Samacheer Kalvi Class 11 Bio Zoology Solutions Chapter 6 Respiration

Part I

I. Choose The Best Options

 

Question 1. Breathing is controlled by
(a) cerebrum
(b) medulla oblongata
(c) cerebellum
(d) pons
Answer: (b) medulla oblongata
In simple words: The medulla oblongata is a special part of your brain that automatically makes you breathe without you even thinking about it. It keeps our breathing steady, ensuring we always get enough air.

🎯 Exam Tip: Remember that the medulla oblongata also controls other vital involuntary actions like heartbeat and digestion, making it a critical part of the brainstem.

 

Question 2. Intercostal muscles are found between the
(a) vertebral column
(b) sternum
(c) ribs
(d) glottis
Answer: (c) ribs
In simple words: Intercostal muscles are located right between your ribs and help them move when you breathe in and out. They are essential for changing the size of your chest cavity during breathing.

🎯 Exam Tip: Distinguish between external and internal intercostal muscles, as they play different roles in inspiration and expiration.

 

Question 3. The respiratory structures of insects are
(a) tracheal tubes
(b) gills
(c) green glands
(d) lungs
Answer: (a) tracheal tubes
In simple words: Insects breathe through tiny tubes called tracheal tubes, which carry air directly to their body cells. Unlike humans, they don't use lungs or blood to transport oxygen.

🎯 Exam Tip: Understand that this direct gas exchange system is highly efficient for small organisms but limits their body size.

 

Question 4. Asthma is caused due to
(a) inflammation of bronchus and bronchioles
(b) inflammation of branchiole
(c) damage of diaphragm
(d) infection of lungs
Answer: (a) inflammation of bronchus and bronchioles
In simple words: Asthma happens when the air tubes in your lungs, called bronchi and bronchioles, get swollen and narrow, making it hard to breathe. This inflammation makes the airways very sensitive and prone to tightening.

🎯 Exam Tip: Recognize that asthma is often triggered by allergens, exercise, or cold air, leading to airway constriction.

 

Question 5. The Oxygen Dissociation Curve is
(a) sigmoid
(b) straight line
(c) curved
(d) rectangular hyperbola
Answer: (a) sigmoid
In simple words: The curve that shows how much oxygen binds to hemoglobin at different oxygen levels has an S-shape, which is called a sigmoid curve. This shape reflects how hemoglobin's ability to bind oxygen changes as oxygen levels increase.

🎯 Exam Tip: Remember that the sigmoid shape indicates cooperative binding, meaning as one oxygen molecule binds, it becomes easier for subsequent ones to bind.

 

Question 6. The Tidal Volume of a normal person is
(a) 800 mL
(b) 1000-1200 mL
(c) 500 mL
(d) 1100-1200 mL
Answer: (c) 500 mL
In simple words: Tidal volume is the amount of air you breathe in or out during a normal, relaxed breath. For most people, this is around 500 milliliters.

🎯 Exam Tip: Clearly differentiate tidal volume from other lung volumes like inspiratory reserve volume or vital capacity.

 

Question 7. During inspiration, the diaphragm
(a) expands
(b) unchanged
(c) relaxes to become domed-shaped
(d) contracts and flattens
Answer: (d) contracts and flattens
In simple words: When you breathe in, the diaphragm muscle moves downwards and becomes flatter. This action makes your chest cavity bigger, allowing air to rush into your lungs.

🎯 Exam Tip: Visualize the diaphragm's movement: contracts and flattens for inspiration, relaxes and domes upwards for expiration.

 

Question 8. CO2 is transported through blood to lungs as
(a) carbonic acid
(b) oxyhaemoglobin
(c) carbamino haemoglobin
(d) carboxy haemoglobin
Answer: (c) carbamino haemoglobin
In simple words: Carbon dioxide is mainly carried in your blood to the lungs by attaching to hemoglobin, forming something called carbaminohemoglobin. This is one of the key ways your body moves waste CO2.

🎯 Exam Tip: Remember the three main forms of CO2 transport: as bicarbonate ions (majority), carbaminohemoglobin, and dissolved in plasma.

 

Question 9. When 1500 mL air is in the lungs, it is called
(a) vital capacity
(b) tidal volume
(c) residual volume
(d) inspiratory reserve volume
Answer: (c) residual volume
In simple words: Even after you breathe out as much as you possibly can, some air always stays in your lungs, and this is called residual volume, typically around 1500 mL. This remaining air keeps your lungs from completely collapsing.

🎯 Exam Tip: Residual volume cannot be measured directly with a spirometer because it's the air that always remains in the lungs.

 

Question 10. Vital capacity is
(a) TV + IRV
(b) TV + ERV
(c) RV + ERV
(d) TV + IRV + ERV
Answer: (d) TV + IRV + ERV
In simple words: Vital capacity is the largest amount of air you can breathe out after taking the biggest possible breath in. It includes the normal breath (tidal volume), the extra air you can inhale (inspiratory reserve volume), and the extra air you can exhale (expiratory reserve volume).

🎯 Exam Tip: Vital capacity represents the maximum exchangeable air in the lungs and is an important measure of lung function.

 

Question 11. After a long deep breath, we do not respire for some seconds due to
(a) more CO2 in the blood
(b) more O2 in the blood
(c) less CO2 in the blood
(d) less O2 in the blood
Answer: (b) more O2 in the blood
In simple words: After taking a very deep breath, your blood has a lot of oxygen, which means your body doesn't feel the need to breathe again right away. The high oxygen levels temporarily suppress the urge to inhale.

🎯 Exam Tip: Remember that breathing rate is primarily controlled by CO2 levels, but very high O2 levels can temporarily override this drive.

 

Question 12. Which of the following substances in tobacco smoke damage the gas exchange system?
(a) carbon monoxide and carcinogens
(b) carbon monoxide and nicotine
(c) carcinogens and tar
(d) nicotine and tar
Answer: (b) carbon monoxide and nicotine
In simple words: Carbon monoxide stops oxygen from properly attaching to your blood, and nicotine is addictive and affects heart rate, both harming your breathing system. Tar also causes significant damage to lung tissue.

🎯 Exam Tip: Note that while carcinogens and tar are also damaging, carbon monoxide and nicotine are particularly potent in disrupting gas exchange and overall respiratory function.

 

Question 13. Column I represents diseases and column II represents their symptoms Choose the correctly paired option.

(a) P – iii, Q – ii, R – i
(b) P – iii, Q – i, R – ii
(c) P – ii, Q – iii, R – i
(d) P – ii, Q – i, R -iii
Answer: (b) P – iii, Q – i, R – ii
In simple words: This matching shows that Asthma is related to allergy, Emphysema often causes recurring bronchitis, and Pneumonia leads to white blood cells building up in the air sacs. Understanding these links helps diagnose breathing problems.

🎯 Exam Tip: For matching questions, systematically go through each option and eliminate incorrect pairs until you find the perfect match.

 

Question 14. Which of the following best describes the process of gas exchange in the lungs?
(a) Air moves in and out of the alveoli during breathing.
(b) Carbon dioxide diffuses from deoxygenated blood in capillaries into the alveolar air
(c) Oxygen and carbon dioxide diffuse down their concentration gradients between blood and alveolar air
(d) Oxygen diffuses from alveolar air into deoxygenated blood.
Answer: (c) Oxygen and carbon dioxide diffuse down their concentration gradients between blood and alveolar air
In simple words: Gases like oxygen and carbon dioxide move between the lungs and blood because they always try to go from an area where there's a lot of them to an area where there's less. This natural movement is called diffusion and is crucial for breathing.

🎯 Exam Tip: Focus on the concept of partial pressure gradients as the driving force for gas exchange, ensuring correct directionality for each gas.

 

Question 15. Make the correct pairs.

(a) P – i, Q – ii, R – iii, S – iv
(b) P – ii, Q – iii R – iv, S – i
(c) P – ii, Q – iii, R – i, S – iv
(d) P – iii, Q – iv, R – i, S – ii
Answer: (d) P – iii, Q – iv, R – i, S – ii
In simple words: This matching correctly links respiratory measurements with their definitions: PIC refers to air inhaled after normal expiration, QEC is air exhaled after inspiration, RVC is the maximum air breathed in forcefully, and SFRC is the air left in lungs after normal expiration. These are different ways to measure lung capacity.

🎯 Exam Tip: Learn the full forms of abbreviations like PIC (Inspiratory Capacity), QEC (Expiratory Capacity), RVC (Residual Volume), and SFRC (Functional Residual Capacity) to understand their definitions better.

 

Question 16. Make the correct pairs.

(a) P – ii, Q – iv, R – i, S – iii
(b) P – iii, Q – ii R – iv, S – i
(c) P – ii, Q – iv, R – iii, S – i
(d) P – iii, Q – iv, R – i, S – ii
Answer: (a) P – ii, Q – iv, R – i, S – iii
In simple words: This match correctly assigns typical volume ranges to lung capacities: Tidal volume is about 500 ml, Residual volume is 1100-1200 ml, Expiratory reserve volume is 1000-1100 ml, and Inspiratory reserve volume is 2500-3000 ml. These values help doctors understand how well your lungs work.

🎯 Exam Tip: Memorize the approximate normal values for different lung volumes and capacities, as they are frequently tested.

 

Question 17. Name the respiratory organs of flatworm earthworm, fish, prawn, cockroach, and cat.
Answer:
Flatworm – Body surface
Earthworm – Moist skin
Fish – Gills
Prawn - Gills
Cockroach – Trachea
Cat-Lungs
In simple words: Different animals breathe in different ways; flatworms use their skin, earthworms use moist skin, fish and prawns use gills, cockroaches use tubes called tracheae, and cats use lungs. This shows how living things adapt to their environment.

🎯 Exam Tip: Pay close attention to the specific respiratory structures of diverse organisms, as they reflect evolutionary adaptations to their habitats.

 

Question 18. Name the enzyme that catalyses the bicarbonate formation in RBCs.
Answer: Carbonic anhydrase
In simple words: The enzyme called carbonic anhydrase helps turn carbon dioxide and water into bicarbonate very quickly inside red blood cells. This is important for moving carbon dioxide out of your body.

🎯 Exam Tip: Remember that carbonic anhydrase is one of the fastest enzymes known, playing a crucial role in maintaining blood pH and efficient gas transport.

 

Question 19. Air moving from the nose to the trachea passes through a number of structures. List in order of the structures.
Answer: External nostrils, Nasal cavity, Pharynx, Larynx, Trachea, Bronchi, Bronchioles, and the Lungs (Alveoli)
In simple words: When you breathe in, air goes from your nose, through your nasal cavity, then pharynx, larynx, trachea, bronchi, bronchioles, and finally reaches the tiny air sacs in your lungs called alveoli. This is the exact path air takes to reach your lungs.

🎯 Exam Tip: Practice drawing the respiratory pathway and labeling each part to reinforce your understanding of the air flow sequence.

 

Question 20. Which structures seal the Larynx when we swallow?
Answer: Epiglottis.
In simple words: The epiglottis is a small flap that covers your voice box (larynx) when you swallow, stopping food from going down the wrong tube into your lungs. It acts like a trapdoor to protect your airway.

🎯 Exam Tip: Understand the critical role of the epiglottis in preventing choking and separating the digestive and respiratory tracts.

 

Question 21. Resistance in the airways is typically low why? Give two reasons.
Answer: The airway resistance is low because:
• The diameter of most airways is relatively large.
• For smaller airways there are many in parallel, making their combined diameter large.
• Air has a low viscosity.
In simple words: Your breathing tubes have low resistance because most of them are wide, and even the tiny ones work together, acting like one big wide tube. Also, air itself isn't thick or sticky.

🎯 Exam Tip: Remember that low airway resistance allows for efficient and easy airflow, crucial for proper gas exchange.

 

Question 22. How the body makes long-term adjustments when living in high altitude?
Answer:
• When a person travels from sea level to elevations where the atmospheric pressure and partial pressure of O2 are lowered, there is a poor binding of O2 with haemoglobin which leads to acute mountain sickness.
• When the person lives there for a long time, the kidney synthesizes erythropoietin which stimulates the bone marrow to produce more RBCs.
In simple words: When people go to high mountains, their bodies get less oxygen, which can make them sick at first. But after a while, their kidneys tell their body to make more red blood cells so they can carry more oxygen.

🎯 Exam Tip: Focus on erythropoietin and increased RBC production as the key long-term adaptation to high altitude, which helps compensate for lower oxygen availability.

 

Question 23. Why is pneumonia considered a dangerous disease?
Answer: Inflammation of the lungs due to infection caused by bacteria or viruses is called pneumonia. The symptoms are sputum production, nasal congestion, shortness of breath, sore throat, etc. The alveoli get filled with fluid or pus, making it difficult to breathe (lung abscesses). Pneumonia is dangerous because it severely affects the body's ability to take in oxygen.
In simple words: Pneumonia is dangerous because it makes your lungs get infected and fill with fluid, so you can't breathe well. This makes it hard for your body to get enough oxygen, which is very serious.

🎯 Exam Tip: Recognize that fluid in the alveoli (air sacs) directly impairs gas exchange, leading to reduced oxygen uptake, which is the primary danger of pneumonia.

 

Question 24. Diffusion of gases occurs in the alveolar region and only not in any other part of the respiratory system discuss.
Answer:
• The other parts of the respiratory system do the work of passing the air into the lungs only.
• Real respiration takes place between alveoli and blood capillaries.
The diffusion membrane of the alveolus is made up of three layers.
1. The thin squamous epithelial cells.
2. The endothelium of the alveolar capillaries.
3. The basement substance found in between them.
The thin squamous epithelial cells of the alveoli provide space for gaseous exchange. This thin barrier allows gases to move quickly.
In simple words: Gas exchange only happens in the alveoli, the tiny air sacs in your lungs, because their walls are super thin and have lots of blood vessels nearby. Other parts of the breathing system just move air around.

🎯 Exam Tip: Emphasize the thinness and large surface area of the alveolar membrane as key adaptations for efficient gas diffusion.

 

Question 25. Sketch a flow chart to show the pathway of airflow during respiration.
Answer: Atmospheric air enters into external nostrils \( \implies \) enters into Nasal cavity \( \implies \) passes into \( \implies \) the pharynx \( \implies \) crosses the larynx and then enters into the trachea \( \implies \) reaches the bronchus into \( \implies \) enters bronchioles \( \implies \) enters into the lungs \( \implies \) there enters into the alveoli where exchange of gases taking place.
In simple words: Air goes from your nose to your nasal cavity, then pharynx, larynx, trachea, bronchi, bronchioles, and finally to the alveoli in your lungs where gases are swapped. This is the full journey air takes inside your body.

🎯 Exam Tip: Clearly represent each structure as a distinct step in the flowchart, ensuring correct anatomical order and use of arrows to show direction.

 

Question 26. Explain the conditions which create problems in oxygen transport?
Answer: When a person travels quickly from sea level to elevations above 8000 ft, where the atmospheric pressure and partial pressure of O2 are lowered, the individual responds with symptoms of acute mountain sickness (AMS)-headache, shortness of breath, nausea, and dizziness due to poor binding of O2 with hemoglobin. When the person moves on a long-term basis to mountains from sea level his body begins to make respiratory and hematopoietic adjustments. To overcome this situation, kidneys accelerate the production of the hormone erythropoietin, which stimulates the bone marrow to produce more RBCs. When a person descends deep into the sea, the pressure in the surrounding water increases which causes the lungs to decrease in volume. This decrease in volume increases the partial pressure of the gases within the lungs. This effect can be beneficial, because it tends to drive additional oxygen into the circulation, but this benefit also has a risk, the increased pressure can also drive nitrogen gas into the circulation. This increase in blood nitrogen content can lead to a condition called nitrogen narcosis. When the diver ascends to the surface too quickly, a condition called 'bends' or decompression sickness occurs and nitrogen comes out of solution while still in the blood-forming bubbles. Small bubbles in the blood are not harmful, but large bubbles can lodge in small capillaries, blocking blood flow or can press on nerve endings. Decompression sickness is associated with pain in joints and muscles and neurological problems including a stroke. The risk of nitrogen narcosis and bends is common in scuba divers. During carbon-dioxide poisoning, the demand for oxygen increases. As the O2 level in the blood decreases, it leads to suffocation and the skin turns bluish-black.
In simple words: Problems in oxygen transport happen when there's not enough oxygen in the air, like on high mountains, or when gases behave strangely under high pressure, like when diving deep underwater. These situations can lead to sickness because the body struggles to get enough oxygen or to release dissolved gases safely.

🎯 Exam Tip: Categorize problems into those caused by low atmospheric pressure (high altitude) and those by high ambient pressure (diving) to better understand the different physiological responses.

Part II

I. Choose The Best Options

 

Question 1. What are the respiratory organs of the Limulus?
(a) Trachea
(b) Gills
(c) Bookgills
(d) Green glands
Answer: (c) Bookgills
In simple words: Limulus, also known as horseshoe crabs, breathe using special structures called bookgills. These gills have many thin layers, like pages in a book, to help them take in oxygen from the water.

🎯 Exam Tip: Differentiate unique respiratory structures like bookgills (found in horseshoe crabs) from typical gills (fish) or tracheae (insects).

 

Question 2. The failure of tissues for any reason to receive an adequate supply of oxygen.
(a) apnoea
(b) Dyspnoea
(c) Hypoxia
(d) Opnia
Answer: (c) Hypoxia
In simple words: When your body's tissues don't get enough oxygen, it's called hypoxia. This can happen for many reasons and is a serious medical condition.

🎯 Exam Tip: Understand the difference between hypoxia (low oxygen in tissues) and hypoxemia (low oxygen in blood), as they are related but distinct conditions.

 

Question 3. These are mucous-secreting cells.
(a) Oxynctic cells
(b) Chief cells
(c) Goblet cells
(d) Parietal cells
Answer: (c) Goblet cells
In simple words: Goblet cells are special cells that make mucus, which is a sticky substance that helps protect the linings of your body, like in your breathing tubes. The mucus traps dust and germs.

🎯 Exam Tip: Remember the protective function of mucus in the respiratory tract, trapping pathogens and particles before they reach the lungs.

 

Question 4. These are the respiratory surfaces.
(a) brunchioles
(b) Terminal bronchiole
(c) alveoli
(d) small bronchi
Answer: (c) alveoli
In simple words: The tiny air sacs in your lungs, called alveoli, are where oxygen and carbon dioxide are swapped between the air and your blood. They are the actual sites where breathing does its main job.

🎯 Exam Tip: Always associate alveoli with the primary site of gas exchange due to their thin walls and rich blood supply.

 

Question 5. What is the average rate of respiration of a healthy man?
(a) 12-16 times
(b) 8-10 times
(c) 5-10 times
(d) 15 - 30 times
Answer: (a) 12-16 times
In simple words: A healthy adult usually breathes about 12 to 16 times every minute when resting. This rate ensures a steady supply of oxygen to the body.

🎯 Exam Tip: Note that resting respiratory rate can vary slightly but is an important indicator of overall health.

 

Question 6. Match:

(a) 1) i – iv; 2) i – i; 3) ii; 4) iii
(b) 1) i – i; 2) ii; 3) iii; 4) iv
(c) 1) i – iii; 2) i; 3) iv; 4) ii
(d) 1) iv; 2) iii; 3) ii; 4) i
Answer: (d) 1) iv; 2) iii; 3) ii; 4) i
In simple words: This matching correctly links respiratory volumes and capacities with their typical numerical values. For example, residual volume is 1100-1200 ml, while total lung capacity is around 6000 ml. Knowing these numbers helps understand how much air your lungs can hold and move.

🎯 Exam Tip: Ensure you accurately recall the typical volume ranges for each lung capacity to avoid common errors in matching questions.

 

Question 7.

(a) 1) i – i; 2) ii; 3) iii; 4) iv
(b) 1) i – ii; 2) iii; 3) i; 4) iv
(c) 1) i – iv; 2) iii; 3) ii; 4) i
(d) 1) i – iv; 2) i; 3) ii; 4) iii
Answer: (c) 1) i – iv; 2) iii; 3) ii; 4) i
In simple words: This matching shows the correct partial pressures of oxygen in different parts of the body. For example, atmospheric air has a very high oxygen pressure, while tissues have a lower pressure because they use up oxygen. This difference in pressure helps oxygen move where it's needed.

🎯 Exam Tip: Accurately recalling the partial pressures of oxygen and carbon dioxide in various physiological locations is fundamental to understanding gas exchange dynamics.

I. Choose The Best Options

 

Question 1. Breathing is controlled by
(a) cerebrum
(b) medulla oblongata
(c) cerebellum
(d) pons
Answer: (b) medulla oblongata
In simple words: The medulla oblongata, located in the brainstem, is the main control center for breathing. It automatically regulates how fast and deep we breathe.

🎯 Exam Tip: Remember that the medulla oblongata is responsible for vital involuntary functions, including heart rate and breathing, making it a key part of the brainstem.

 

Question 2. Intercostal muscles are found between the
(a) vertebral column
(b) sternum
(c) ribs
(d) glottis
Answer: (c) ribs
In simple words: The intercostal muscles are located in the spaces between your ribs. They help move the rib cage up and down during breathing, making your chest expand and contract.

🎯 Exam Tip: When describing the location of muscles, visualize the skeletal structure. "Inter-" always means "between" so "intercostal" refers to the space between the "costa" (ribs).

 

Question 3. The respiratory structures of insects are
(a) tracheal tubes
(b) gills
(c) green glands
(d) lungs
Answer: (a) tracheal tubes
In simple words: Insects breathe through a system of tiny tubes called tracheae. These tubes open to the outside through small holes and carry air directly to their body cells.

🎯 Exam Tip: Distinguish between respiratory organs of different animal groups. Insects use tracheae, fish use gills, and mammals use lungs, each adapted to their environment.

 

Question 4. Asthma is caused due to
(a) inflammation of bronchus and bronchioles
(b) inflammation of branchiole
(c) damage of diaphragm
(d) infection of lungs
Answer: (a) inflammation of bronchus and bronchioles
In simple words: Asthma occurs when the air passages in the lungs, like the bronchi and bronchioles, become inflamed and narrow. This makes it hard to breathe and can cause wheezing.

🎯 Exam Tip: Focus on the specific parts of the respiratory system affected by diseases. Asthma primarily involves inflammation and narrowing of the airways.

 

Question 5. The Oxygen Dissociation Curve is
(a) sigmoid
(b) straight line
(c) curved
(d) rectangular hyperbola
Answer: (a) sigmoid
In simple words: The oxygen dissociation curve, which shows how much oxygen binds to hemoglobin at different oxygen levels, has an S-shape. This sigmoid shape shows how hemoglobin's ability to pick up oxygen changes.

🎯 Exam Tip: Visualizing key biological curves helps understand physiological processes. The sigmoid shape of the oxygen dissociation curve is crucial for efficient oxygen transport and release.

 

Question 6. The Tidal Volume of a normal person is
(a) 800 mL
(b) 1000-1200 mL
(c) 500 mL
(d) 1100-1200 mL
Answer: (c) 500 mL
In simple words: Tidal volume is the amount of air a person breathes in or out during a normal, relaxed breath. For an adult, this is usually about 500 milliliters.

🎯 Exam Tip: Know the typical values for lung volumes. Tidal volume is a fundamental measure representing the air exchanged during quiet breathing.

 

Question 7. During inspiration, the diaphragm
(a) expands
(b) unchanged
(c) relaxes to become domed-shaped
(d) contracts and flattens
Answer: (d) contracts and flattens
In simple words: When you breathe in, your diaphragm muscle tightens and moves downwards, becoming flatter. This action makes your chest cavity bigger, allowing air to rush into your lungs.

🎯 Exam Tip: Remember the opposing actions: during inspiration, the diaphragm contracts and flattens; during expiration, it relaxes and becomes dome-shaped.

 

Question 8. CO2 is transported through blood to lungs as
(a) carbonic acid
(b) oxyhaemoglobin
(c) carbamino haemoglobin
(d) carboxy haemoglobin
Answer: (c) carbamino haemoglobin
In simple words: Carbon dioxide is carried in the blood in a few ways. One important way is when it attaches to hemoglobin, forming carbaminohemoglobin, which then travels to the lungs.

🎯 Exam Tip: Note the different forms of gas transport: oxygen as oxyhemoglobin, carbon dioxide mainly as bicarbonate ions, but also significantly as carbaminohemoglobin and dissolved in plasma.

 

Question 9. When 1500 mL air is in the lungs, it is called
(a) vital capacity
(b) tidal volume
(c) residual volume
(d) inspiratory reserve volume
Answer: (c) residual volume
In simple words: Residual volume is the amount of air that always stays in your lungs, even after you try to push out as much air as possible. It is essential to keep the alveoli open.

🎯 Exam Tip: Distinguish residual volume from other lung capacities. It's the air that cannot be exhaled, preventing lung collapse.

 

Question 10. Vital capacity is
(a) TV + IRV
(b) TV + ERV
(c) RV + ERV
(d) TV + IRV + ERV
Answer: (d) TV + IRV + ERV
In simple words: Vital capacity is the maximum amount of air a person can exhale after taking the deepest possible breath. It includes the normal breath volume plus all the extra air that can be breathed in and out.

🎯 Exam Tip: Clearly know the formulas for different lung capacities. Vital capacity is the sum of tidal volume (TV), inspiratory reserve volume (IRV), and expiratory reserve volume (ERV).

 

Question 11. After a long deep breath, we do not respire for some seconds due to
(a) more CO2 in the blood
(b) more O2 in the blood
(c) less CO2 in the blood
(d) less O2 in the blood
Answer: (b) more O2 in the blood
In simple words: When you take a deep breath, your blood gets a lot of oxygen. This high oxygen level temporarily slows down the breathing signal to the brain, so you don't feel the need to breathe right away.

🎯 Exam Tip: While oxygen levels influence breathing, the primary trigger for breathing is usually the buildup of carbon dioxide in the blood. However, a very high \( O_2 \) can briefly suppress the urge to breathe.

 

Question 12. Which of the following substances in tobacco smoke damage the gas exchange system?
(a) carbon monoxide and carcinogens
(b) carbon monoxide and nicotine
(c) carcinogens and tar
(d) nicotine and tar
Answer: (b) carbon monoxide and nicotine
In simple words: Tobacco smoke contains harmful substances like carbon monoxide and nicotine. Carbon monoxide reduces oxygen transport, and nicotine narrows blood vessels, both negatively affecting the body's gas exchange and overall health.

🎯 Exam Tip: Remember the specific effects of each component in tobacco smoke. Carbon monoxide impacts oxygen transport, while nicotine affects the cardiovascular system and causes addiction.

 

Question 13. Column I represents diseases and column II represents their symptoms Choose the correctly paired option.

(a) P - iii, Q - ii, R - i
(b) P - iii, Q - i, R - ii
(c) P - ii, Q - iii, R - i
(d) P - ii, Q - i, R -iii
Answer: (b) P - iii, Q - i, R - ii
In simple words: Asthma is often triggered by allergies. Emphysema can lead to recurring bronchitis. Pneumonia is characterized by white blood cells (W.B.C) accumulating in the alveoli.

🎯 Exam Tip: When matching diseases and symptoms, recall the primary characteristics of each condition to make the correct links.

 

Question 14. Which of the following best describes the process of gas exchange in the lungs?
(a) Air moves in and out of the alveoli during breathing.
(b) Carbon dioxide diffuses from deoxygenated blood in capillaries into the alveolar air
(c) Oxygen and carbon dioxide diffuse down their concentration gradients between blood and alveolar air
(d) Oxygen diffuses from alveolar air into deoxygenated blood.
Answer: (c) Oxygen and carbon dioxide diffuse down their concentration gradients between blood and alveolar air
In simple words: Gas exchange in the lungs happens because oxygen and carbon dioxide naturally move from an area where there is more of them to an area where there is less. This concentration difference drives them across the lung and blood barriers.

🎯 Exam Tip: The principle of diffusion down concentration gradients is fundamental to understanding gas exchange in both the lungs and tissues.

 

Question 15. Make the correct pairs.

(a) P - i, Q - ii, R - iii, S - iv
(b) P - ii, Q - iii R - iv, S - i
(c) P - ii, Q - iii, R - i, S - iv
(d) P - iii, Q - iv, R - i, S - ii
Answer: (d) P - iii, Q - iv, R - i, S - ii
In simple words: This question pairs lung capacity terms with their descriptions. PIC (Inspiratory Capacity) is the maximum air breathed in after normal expiration. QEC (Expiratory Capacity) is the maximum air exhaled after normal inspiration. RVC (Residual Volume) is the air left in lungs after maximal expiration. SFRC (Functional Residual Capacity) is the air remaining in the lungs after a normal expiration.

🎯 Exam Tip: Carefully learn the definitions of lung volumes and capacities, as they are often tested with matching questions.

 

Question 16. Make the correct pairs.

(a) P - ii, Q - iv, R - i, S - iii
(b) P - iii, Q - ii R - iv, S - i
(c) P - ii, Q - iv, R - iii, S - i
(d) P - iii, Q - iv, R - i, S - ii
Answer: (a) P - ii, Q - iv, R - i, S - iii
In simple words: Tidal volume (P) is about 500 ml (ii). Residual volume (Q) is roughly 1100-1200 ml (iv). Expiratory reserve volume (R) is about 1000-1100 ml (i). Inspiratory reserve volume (S) is around 2500-3000 ml (iii). These are the typical amounts of air associated with different breathing actions.

🎯 Exam Tip: Mastering the numerical ranges for different lung volumes (like tidal, residual, inspiratory, expiratory) is crucial for respiratory physiology questions.

 

Question 17. Name the respiratory organs of flatworm earthworm, fish, prawn, cockroach, and cat.
Answer:
Flatworm - Body surface
Earthworm - Moist skin
Fish - Gills
Prawn - Gills
Cockroach - Trachea
Cat - Lungs
In simple words: Different animals have special body parts for breathing. Flatworms and earthworms breathe through their skin. Fish and prawns use gills. Cockroaches use tiny tubes called tracheae, and cats breathe with lungs, just like humans.

🎯 Exam Tip: Understand how respiratory organs are adapted to the environment and lifestyle of different organisms. Simple organisms use body surfaces, while complex ones have specialized structures.

 

Question 18. Name the enzyme that catalyses the bicarbonate formation in RBCs.
Answer: Carbonic anhydrase
In simple words: Carbonic anhydrase is an enzyme found in red blood cells that quickly helps turn carbon dioxide and water into carbonic acid. This step is important for carrying carbon dioxide in the blood.

🎯 Exam Tip: Remember carbonic anhydrase as a key enzyme in carbon dioxide transport, facilitating its conversion into bicarbonate ions.

 

Question 19. Air moving from the nose to the trachea passes through a number of structures. List in order of the structures.
Answer: External nostrils, Nasal cavity, Pharynx, Larynx, Trachea, the bronchi, bronchioles, and the lungs (alveoli)
In simple words: Air first enters through your nostrils, then goes into your nasal cavity. After that, it moves through the pharynx and larynx, then down the trachea. From there, it goes into smaller tubes called bronchi and bronchioles, finally reaching the tiny air sacs in the lungs called alveoli.

🎯 Exam Tip: Be able to trace the complete pathway of air through the respiratory system, starting from entry to the site of gas exchange. This sequence is important for understanding how air is conditioned and transported.

 

Question 20. Which structures seal the Larynx when we swallow?
Answer: Epiglottis.
In simple words: When you swallow, a small flap called the epiglottis closes over the larynx (voice box). This stops food and liquids from going into your windpipe and lungs, preventing choking.

🎯 Exam Tip: The epiglottis plays a crucial role in preventing aspiration during swallowing, acting as a protective barrier for the respiratory tract.

 

Question 21. Resistance in the airways is typically low why? Give two reasons.
Answer: The airway resistance is low because:

• The diameter of most airways is relatively large.
• For smaller airways there are many in parallel, making their combined diameter large.
• Air has a low viscosity.

In simple words: Air flows easily in our airways for two main reasons: first, the main breathing tubes are wide. Second, even the tiny air passages are numerous and arranged in parallel, which together offer a large pathway for air to flow smoothly. Air itself is also not very thick or sticky, making it easy to move.

🎯 Exam Tip: Explain resistance in terms of the physical properties of the airways (diameter, branching) and the air itself (viscosity). The large total cross-sectional area of smaller airways keeps overall resistance low.

 

Question 22. How the body makes long-term adjustments when living in high altitude?
Answer:

• When a person travels from sea level to elevations where the atmospheric pressure and partial pressure of \( O_2 \) is lowered, a poor binding of \( O_2 \) with hemoglobin leads to acute mountain sickness.
• When the person lives there for a long time, the kidney synthesizes erythropoietin which stimulates the bone marrow to produce more RBCs.

In simple words: At high altitudes, there is less oxygen in the air. To cope, the body makes more red blood cells (RBCs) to carry more oxygen. This happens because the kidneys produce a hormone called erythropoietin, which tells the bone marrow to make more RBCs. This helps the body get enough oxygen even with less in the air.

🎯 Exam Tip: Long-term adaptation to high altitude involves an increase in red blood cell count, primarily stimulated by erythropoietin from the kidneys, to improve oxygen-carrying capacity.

 

Question 23. Why is pneumonia considered a dangerous disease?
Answer: Inflammation of the lungs due to infection caused by bacteria or viruses is called pneumonia. The symptoms are sputum production, nasal congestion, shortness of breath, sore throat, etc. The alveoli get filled with fluid or pus, making it difficult to breathe (lung abscesses). Pneumonia is dangerous because it can severely impair the lungs' ability to exchange gases, potentially leading to respiratory failure.
In simple words: Pneumonia is serious because it causes the lungs to get swollen and filled with fluid or pus due to an infection. This makes it very hard to breathe and get enough oxygen, which can be life-threatening.

🎯 Exam Tip: Highlight the key physiological impact of pneumonia: inflammation and fluid accumulation in the alveoli, leading to impaired gas exchange and severe breathing difficulties.

 

Question 24. Diffusion of gases occurs in the alveolar region and only not in any other part of the respiratory system discuss.
Answer:

• The other parts of the respiratory system do the work of passing the air into the lungs only.
• Real respiration takes place between alveoli and blood capillaries.

The diffusion membrane of the alveolus is made up of three layers.
1. The thin squamous epithelial cells.
2. The endothelium of the alveolar capillaries.
3. The basement substance found in between them.
The thin squamous epithelial cells of the alveoli provide space for gaseous exchange.
In simple words: Gas exchange, where oxygen enters the blood and carbon dioxide leaves, happens mainly in the alveoli, which are tiny air sacs in the lungs. This is because the alveoli have very thin walls, made of three super-thin layers, allowing gases to easily pass between the air and the blood. Other parts of the breathing system just move air in and out.

🎯 Exam Tip: Emphasize the thinness and large surface area of the alveolar-capillary membrane as crucial adaptations for efficient gas diffusion, unlike other thicker parts of the respiratory tract.

 

Question 25. Sketch a flow chart to show the pathway of airflow during respiration.
Answer: Atmospheric air enters into external nostrils
\( \implies \) enters into Nasal cavity
\( \implies \) passes into the pharynx
\( \implies \) crosses the larynx and then enters into the trachea
\( \implies \) reaches the bronchus
\( \implies \) enters bronchioles
\( \implies \) enters into the lungs
\( \implies \) there enters into the alveoli where exchange of gases takes place.
In simple words: Air starts at your nose, goes through your nasal cavity, then your throat (pharynx and larynx), down your windpipe (trachea). It then splits into smaller tubes (bronchi, then bronchioles) and finally reaches tiny air sacs (alveoli) in your lungs, where oxygen enters your blood.

🎯 Exam Tip: When listing a pathway, ensure all key structures are included in the correct sequential order. Using arrows or bullet points clearly shows the flow.

 

Question 26. Explain the conditions which create problems in oxygen transport?
Answer: When a person travels quickly from sea level to elevations above 8000 ft, where the atmospheric pressure and partial pressure of \( O_2 \) are lowered, the individual responds with symptoms of acute mountain sickness (AMS) - headache, shortness of breath, nausea, and dizziness due to poor binding of \( O_2 \) with hemoglobin. When the person moves on a long-term basis to mountains from sea level, his body begins to make respiratory and hematopoietic adjustments. To overcome this situation, kidneys accelerate the production of the hormone erythropoietin, which stimulates the bone marrow to produce more RBCs. When a person descends deep into the sea, the pressure in the surrounding water increases which causes the lungs to decrease in volume. This decrease in volume increases the partial pressure of the gases within the lungs. This effect can be beneficial, because it tends to drive additional oxygen into the circulation, but this benefit also has a risk, the increased pressure can also drive nitrogen gas into the circulation. This increase in blood nitrogen content can lead to a condition called nitrogen narcosis. When the diver ascends to the surface too quickly a condition called 'bends' or decompression sickness occurs and nitrogen comes out of solution while still in the blood-forming bubbles. Small bubbles in the blood are not harmful, but large bubbles can lodge in small capillaries, blocking blood flow or can press on nerve endings. Decompression sickness is associated with pain in joints and muscles and neurological problems including a stroke. The risk of nitrogen narcosis and bends is common in scuba divers. During carbon-dioxide poisoning, the demand for oxygen increases. As the \( O_2 \) level in the blood decreases it leads to suffocation and the skin turns bluish-black.
In simple words: Oxygen transport can have problems at high altitudes due to low oxygen, causing mountain sickness, where the body makes more red blood cells to adapt. Deep-sea diving also poses risks; high pressure can lead to nitrogen narcosis or "the bends" if one ascends too quickly, causing nitrogen bubbles to form in the blood. Also, carbon monoxide poisoning reduces oxygen availability, leading to bluish skin and suffocation.

🎯 Exam Tip: Address how both high altitude (low pressure) and deep-sea diving (high pressure) can impact oxygen transport and cause specific medical conditions like AMS, nitrogen narcosis, and decompression sickness.

II. Very Short Questions

 

Question 1. What is excretion?
Answer: Excretion is the exchange of oxygen and carbon dioxide between the environment and cells of our body, where organic nutrients are broken down oxygenatically to release energy. This essential process allows our bodies to fuel all cellular activities.
In simple words: Excretion is the process where the body takes in oxygen and uses it to break down food for energy, while also getting rid of carbon dioxide.

🎯 Exam Tip: Remember to define excretion as the process of eliminating metabolic waste products from the body to maintain homeostasis.

 

Question 2. How much air can be respired by a normal human adult?
Answer: A normal adult can respire approximately 6000 to 8000 ml of air per minute. During vigorous exercise, the tidal volume is about 4-10 times higher, demonstrating the body's adaptability.
In simple words: A typical adult breathes in and out about 6000 to 8000 milliliters of air every minute. When exercising hard, the amount of air they breathe with each breath can increase by 4 to 10 times.

🎯 Exam Tip: Be sure to distinguish between tidal volume (normal breath) and minute ventilation (total air per minute), and how these values change during activity.

 

Question 3. The rate of breathing in aquatic animals is faster than the of terrestrial animals. Give reason.
Answer: The amount of dissolved oxygen is very low in water compared to the amount of oxygen in the air. Hence, the rate of breathing in aquatic animals is faster than that of terrestrial animals to compensate for the lower oxygen availability.
In simple words: Aquatic animals breathe faster than land animals because there is much less oxygen dissolved in water compared to the air. They need to process more water to get enough oxygen.

🎯 Exam Tip: The principle of gas solubility and availability directly impacts respiratory rates across different environments and organisms. Low oxygen concentration requires higher ventilation rates.

 

Question 4. What is residual volume?
Answer: The residual volume is the volume of air remaining in the lungs after a forceful expiration. For instance, in adults, it typically ranges from 1100-1200ml. This air prevents the lungs from completely collapsing.
In simple words: Residual volume is the amount of air that always stays in your lungs, even after you try to push out as much air as possible. It usually ranges from 1100 to 1200 milliliters.

🎯 Exam Tip: Remember that residual volume is the air that can never be fully exhaled and is essential for maintaining lung inflation and continuous gas exchange.

 

Question 5. What is the function of epiglottis?
Answer: The epiglottis is a thin, elastic flap located at the junction of the nasopharynx and larynx. Its main function is to prevent food from entering the larynx and windpipe, thus avoiding choking on food.
In simple words: The epiglottis is a small, flexible flap located at the back of your throat. Its job is to close over your windpipe when you swallow, making sure food goes down your food pipe and not into your lungs, which prevents choking.

🎯 Exam Tip: The epiglottis is a key structure for separating the digestive and respiratory pathways, ensuring food and liquid do not enter the lungs.

 

Question 6. What is meant by inspiratory capacity?
Answer: Inspiratory capacity is the total amount of air a person can breathe in after a normal exhale. This includes the air breathed in normally (tidal volume) plus any extra air they can inhale (inspiratory reserve volume). The formula for inspiratory capacity is \( IC = TV + IRV \).
In simple words: It's how much air you can take into your lungs after a normal breath out. It combines your normal breath and an extra deep breath.

🎯 Exam Tip: To remember this, think of "inspiratory" as "breathing in" and "capacity" as "how much total."

 

Question 7. What is expiratory capacity?
Answer: Expiratory capacity is the total amount of air a person can breathe out after a normal inhale. This includes the air breathed out normally (tidal volume) and any extra air they can forcefully exhale (expiratory reserve volume). The formula for expiratory capacity is \( EC = TV + ERV \).
In simple words: It's how much air you can push out of your lungs after a normal breath in. It combines your normal breath out and an extra forceful breath out.

🎯 Exam Tip: Contrast with inspiratory capacity; "expiratory" means "breathing out."

 

Question 8. How are lungs protected?
Answer: Our lungs are soft, spongy organs found inside the chest. They are kept safe within an airtight space called the thoracic cavity. This cavity is protected at the back by the backbone (vertebral column), in the front by the chest bone (sternum), and on the sides by the ribs. Below the lungs is a dome-shaped muscle called the diaphragm, which also helps protect them.
In simple words: Lungs are protected by our ribs, backbone, and chest bone in an airtight box called the chest cavity. A muscle below, called the diaphragm, also helps.

🎯 Exam Tip: Remember the key bony structures: ribs, sternum, vertebral column, and the muscular diaphragm.

 

Question 9. What is meant by minute respiratory volume?
Answer: Minute respiratory volume is the total amount of air that moves into and out of our lungs each minute. For a normal adult, the tidal volume (air per breath) is about 500 ml, and they breathe about 12 times per minute. So, the minute respiratory volume is typically 6 liters per minute (500 ml x 12 = 6000 ml = 6 liters).
In simple words: It's the total air you breathe in and out in one minute. You can calculate it by multiplying how much air you breathe in one go by how many breaths you take per minute.

🎯 Exam Tip: Understand that "minute respiratory volume" combines both the volume per breath and the breathing rate over a minute.

 

Question 10. What are the characteristic features of the respiratory surface?
Answer: A good respiratory surface has specific features to help with gas exchange. First, it must be very large to allow a lot of gas to be exchanged quickly. Second, it needs many blood vessels right next to it to carry gases away. Third, it must be extremely thin and moist, making it easy for gases to pass through. Finally, it should be directly exposed to the outside air or water to get oxygen and release carbon dioxide, and its membrane must allow respiratory gases to pass through easily.
In simple words: A good breathing surface is big, has lots of blood, is very thin and wet, and lets breathing gases go through easily.

🎯 Exam Tip: Key characteristics are large surface area, rich blood supply, thinness, moisture, and permeability.

 

Question 11. Give short notes on a shaped cartilage of bronchi?
Answer: The bronchi, which are air tubes in our lungs, have C-shaped cartilage rings. These strong, flexible rings act like a support structure. They prevent the air passages from collapsing or bursting open when the air pressure inside changes during breathing. This ensures that air can always flow freely.
In simple words: Bronchi have C-shaped rings made of cartilage. These rings keep the air tubes open so they don't flatten or break when we breathe.

🎯 Exam Tip: The C-shaped cartilage is crucial for maintaining the patency (openness) of the airways, especially during pressure changes.

 

Question 12. What should be the characteristic features of the respiratory surface?
Answer: The features of an effective respiratory surface include having a very large area and a rich supply of blood vessels, which are vital for efficient gas exchange. It must also be very thin and consistently moist, allowing gases to dissolve and pass through easily. Furthermore, it needs to be in direct contact with the external environment, whether that's air or water, and its membrane must be fully permeable to respiratory gases like oxygen and carbon dioxide.
In simple words: For proper breathing, the surface must be big, have lots of blood, be very thin and wet, and let gases move through it easily.

🎯 Exam Tip: Recognize that these features ensure maximum and efficient exchange of oxygen and carbon dioxide.

 

Question 13. What is meant by breathing?
Answer: Breathing is the process where air moves in and out of the lungs. It involves taking oxygen from the atmosphere into our bodies and releasing carbon dioxide from our bodies back into the atmosphere. This continuous movement of air is essential for life.
In simple words: Breathing is simply air going into and out of our lungs, bringing in oxygen and taking out carbon dioxide.

🎯 Exam Tip: Differentiate breathing (mechanical air movement) from respiration (cellular gas exchange).

 

Question 14. Name the muscle that helps in respiration?
Answer: Several muscles work together to help us breathe. The main muscle is the diaphragm, a large, dome-shaped muscle located below the lungs. Other important muscles are the intercostal muscles, which are found between the ribs. These include both external and internal intercostal muscles, all playing a role in moving the rib cage during inhalation and exhalation.
In simple words: The diaphragm (a big muscle under your lungs) and the muscles between your ribs (intercostal muscles) help you breathe.

🎯 Exam Tip: Remember that the diaphragm is the primary muscle, but intercostal muscles also have a significant role.

 

Question 15. What is meant by expiratory reserve volume?
Answer: Expiratory reserve volume (ERV) is the extra amount of air a person can forcefully breathe out after a normal exhalation. This is the air you can push out with effort even after breathing out normally. For an average person, this volume is usually between 1000 and 1100 ml.
In simple words: It's the extra air you can force out of your lungs after you've already breathed out normally. It's like an additional puff of air.

🎯 Exam Tip: Think of ERV as the "extra push" of air you can exhale beyond a normal breath.

 

Question 16. What is the cause for the reduction in the elasticity of the lungs?
Answer: The elasticity of our lungs comes from a special protein called elastin, found in the connective tissues around the tiny air sacs (alveoli). When lungs are healthy, this elastin helps them stretch and recoil easily. However, in conditions like emphysema and chronic bronchitis, an enzyme called elastase can destroy this elastin. When elastin is damaged, the lungs lose their ability to stretch and shrink, making it very hard to breathe out.
In simple words: Lungs are stretchy because of a protein called elastin. Diseases like emphysema damage this elastin, making the lungs stiff and hard to push air out.

🎯 Exam Tip: Connect "elastin" with "elasticity" and its destruction by "elastase" in diseases like emphysema.

 

Question 17. Give notes on Asthma.
Answer: Asthma is a long-term respiratory condition often triggered by allergens, which are substances that cause an allergic reaction. These allergens can include things like dust, pollen, or certain foods such as seafood. When someone with asthma encounters an allergen, their body reacts with an inflammatory response. This causes the airways in the lungs to swell and narrow, making it difficult to breathe, often leading to symptoms like sneezing and coughing.
In simple words: Asthma is a breathing problem caused by things like dust or pollen. When these trigger it, your airways get swollen and narrow, making you cough and feel breathless.

🎯 Exam Tip: Focus on the key words: "allergens," "inflammatory response," "narrowing of airways," and common symptoms like "sneezing and coughing."

 

Question 18. Why do some people snore?
Answer: Snoring happens during sleep when a person breathes with a loud, rough sound. This sound is caused by the vibration of the soft palate, a tissue at the back of the roof of the mouth. It occurs because the upper airway (parts of the nose and throat) becomes partly blocked, making the passage too narrow for air to flow smoothly. As air struggles to pass through this tight space, the soft tissues around it vibrate, creating the characteristic snoring sound.
In simple words: Snoring happens when air can't flow easily through a narrow throat during sleep. This makes the soft tissues in the throat vibrate and create a loud noise.

🎯 Exam Tip: Key factors for snoring are a partially blocked airway and the vibration of soft tissues, particularly the soft palate.

 

Question 19. Why we should not laugh loudly during eating.
Answer: We should avoid laughing loudly while eating because of the way our throat is structured. Both the food pipe (oesophagus) and the windpipe (trachea) are close together in the pharynx. Normally, a thin, flexible flap called the epiglottis covers the windpipe when we swallow, stopping food from going into the lungs. If we talk or laugh while swallowing, this action can disrupt the epiglottis, causing it to fail to close the windpipe properly. This allows food to accidentally enter the windpipe, which can lead to choking or coughing.
In simple words: Don't laugh while eating because a flap called the epiglottis covers your windpipe when you swallow. If you laugh, this flap might not close fully, and food could go into your windpipe instead of your food pipe, making you choke.

🎯 Exam Tip: The epiglottis is the key structure; its primary function is to prevent food from entering the trachea during swallowing.

 

Question 20. Breathing through the nose is healthy than through the mouth? why?
Answer: Breathing through the nose is healthier than breathing through the mouth because the nose acts as a natural filter. The air we breathe contains dust and tiny germs (microbes). When we inhale through the nose, small hairs (bristles) and a sticky lining (mucous membrane) in the nasal cavity trap these particles, preventing them from reaching the lungs. If we breathe through the mouth, these dust and microbes bypass this filtering system and can enter the body, potentially ending up in the stomach or lungs.
In simple words: Breathing through your nose is better because your nose hairs and sticky lining trap dust and germs in the air, stopping them from entering your body. Your mouth does not have this filter.

🎯 Exam Tip: The nasal cavity's filtering mechanism (hairs and mucus) is the primary reason for preferring nasal breathing.

 

Question 21. Write the structure of the alveoli.
Answer: Alveoli are tiny air sacs in the lungs where gas exchange occurs. Their structure is designed for efficiency:

1. Diffusion Membrane: This membrane, where gases cross, has three very thin layers.
   • Thin Squamous Epithelial Cells: The inner lining of the alveolus itself is made of extremely thin, flat cells called Type-I pneumocytes. These cells are very thin, allowing gases to pass through quickly.
   • Endothelium of Alveolar Capillaries: The next layer is the wall of the tiny blood vessels (capillaries) that surround the alveolus.
   • Basement Substance: A thin layer exists between these two cell layers.
2. Type-II Cells: Besides the thin Type-I cells, some thicker cells called Type-II pneumocytes are also present in the alveoli. These cells produce and release a special substance called surfactant, which helps keep the alveoli from collapsing.

In simple words: Alveoli are tiny air sacs with very thin walls made of three layers, including special cells (Type-I) for gas exchange and other cells (Type-II) that make a substance (surfactant) to keep them open.

🎯 Exam Tip: Remember the three layers of the diffusion membrane and the roles of Type-I and Type-II pneumocytes.

 

Question 22. Give the passage of breathing.
Answer: The path air takes during breathing starts when it enters the body through the external nostrils. From there, it goes into the nasal cavity, then passes through the pharynx (throat) and the larynx (voice box). Next, the air moves down into the main air tubes called bronchi, which then branch into smaller tubes called bronchioles. Finally, the air reaches the tiny air sacs known as alveoli, which are located inside the lungs, where oxygen and carbon dioxide are exchanged.
In simple words: Air goes from your nose, through your nasal cavity, pharynx, larynx, bronchi, and bronchioles, until it reaches the alveoli inside your lungs.

🎯 Exam Tip: Memorize the sequence of structures in the respiratory pathway.

 

III. Short Questions

 

Question 1. What is meant by dead space?
Answer: Dead space refers to the volume of air that is breathed in but does not participate in gas exchange. This air fills parts of the respiratory system, like the nose, pharynx, larynx, trachea, and bronchi, but never reaches the alveoli where oxygen and carbon dioxide are swapped. Since gas exchange doesn't happen in these areas, the air there is considered "dead air." In humans, this volume is typically around 150 ml.
In simple words: Dead space is the air you breathe in that doesn't reach the lung parts where oxygen and carbon dioxide are exchanged. It just fills the breathing tubes. This is about 150 ml of air.

🎯 Exam Tip: Distinguish between anatomical dead space (air in conducting airways) and physiological dead space (anatomical plus non-functional alveoli).

 

Question 2. Give an account of the structures of haemoglobin?
Answer: Hemoglobin (Hb) is a complex protein found in red blood cells that carries oxygen. It is a type of conjugated protein, meaning it has a non-protein part attached. This non-protein part, called heme, contains iron and makes up about 4% of hemoglobin. Heme is responsible for binding oxygen. The remaining and larger part of hemoglobin is a colorless protein called globin. Hemoglobin has a molecular weight of around 68,000. Each hemoglobin molecule contains four iron atoms, and each of these iron atoms can bind with one molecule of oxygen, allowing a single hemoglobin molecule to carry four oxygen molecules.
In simple words: Hemoglobin is a protein in red blood cells that carries oxygen. It's mostly a protein called globin, with a small part called heme that has iron. Each hemoglobin can pick up four oxygen molecules. It is a large molecule.

🎯 Exam Tip: Key components are heme (with iron) and globin, and its ability to carry four oxygen molecules.

 

Question 3. What is meant by methaemoglobin?
Answer: Methaemoglobin is a form of hemoglobin where the iron in the heme part is in the ferric (\( Fe^{3+} \)) state, instead of its normal ferrous (\( Fe^{2+} \)) state. In its normal ferrous state, hemoglobin can bind to oxygen. However, when iron is in the ferric state, methaemoglobin loses its ability to bind and transport oxygen effectively. This can reduce the blood's oxygen-carrying capacity.
In simple words: Methaemoglobin is like regular hemoglobin, but its iron part is changed, so it cannot carry oxygen. Normally, hemoglobin has a certain type of iron, but in methaemoglobin, the iron is different and can't pick up oxygen.

🎯 Exam Tip: The crucial difference is the oxidation state of iron (ferric vs. ferrous) and the resulting loss of oxygen-binding capacity.

 

Question 4. What Are Surfactants?
Answer: Surfactants are special substances that form a thin, non-cellular film. This film is made of proteins and phospholipids, and it covers the inner surface of the alveolar membrane in the lungs. Their main job is to reduce the surface tension inside the tiny air sacs (alveoli), which helps prevent them from collapsing when we exhale.
In simple words: Surfactants are a thin layer of proteins and fats that line your lung's air sacs. They help keep the air sacs open so they don't stick together when you breathe out.

🎯 Exam Tip: Remember that surfactants are a protein-phospholipid mix and their key function is reducing surface tension to prevent alveolar collapse.

 

Question 5. What are the significances of surfactants?
Answer: Surfactants play several important roles in the lungs. Their primary significance is to lower the surface tension within the alveoli (tiny air sacs). This reduction in surface tension helps to keep the alveoli open and prevents them from collapsing, especially during exhalation. Additionally, surfactants help to prevent pulmonary edema, which is the accumulation of fluid in the lungs, by maintaining the correct fluid balance in the alveoli.
In simple words: Surfactants are important because they make sure the air sacs in your lungs stay open and don't collapse. They also help stop fluid from building up in your lungs.

🎯 Exam Tip: Two main functions: prevent alveolar collapse (by reducing surface tension) and prevent pulmonary edema.

 

Question 6. What is new born respiratory distress syndrome (NRDS)?
Answer: Newborn Respiratory Distress Syndrome (NRDS) is a breathing problem seen in premature babies. It happens because these babies are born with low levels of surfactant in their lungs. Surfactant is a substance crucial for keeping the tiny air sacs (alveoli) open. Since the production of surfactant usually starts only after the 25th week of pregnancy, babies born very early might not have enough, leading to difficulties in breathing.
In simple words: NRDS is when premature babies have trouble breathing because their lungs don't have enough surfactant, a substance that helps keep lung air sacs open. This happens because surfactant is made late in pregnancy.

🎯 Exam Tip: Key points are "premature babies," "low surfactant levels," and "alveolar collapse."

 

Question 7. What is the reason for yawning?
Answer: Yawning is a reflex action often triggered when there's a slight shortage of oxygen in the body. Our brain detects this imbalance in oxygen demand and sends a signal to the central nervous system (CNS) to initiate a yawn. The act of yawning involves taking a deep, involuntary breath, which helps to bring more oxygen into the lungs and increase blood oxygen levels. It's the body's way of quickly getting more oxygen when needed.
In simple words: We yawn when our body senses it needs more oxygen. Yawning makes us take a deep breath, bringing more oxygen into our lungs and helping to balance our oxygen levels.

🎯 Exam Tip: Yawning is primarily a response to a perceived oxygen deficit, helping to increase oxygen intake.

 

Question 8. Why are hiccups occured?
Answer: Hiccups are involuntary spasms of the diaphragm, the main muscle involved in breathing, often combined with a sudden closure of the vocal cords. They can happen for various reasons, such as eating or drinking too quickly, which might irritate the diaphragm. These spasms cause a sudden intake of breath, which is then abruptly stopped by the closing vocal cords, creating the "hic" sound.
In simple words: Hiccups happen when your diaphragm muscle, which helps you breathe, suddenly twitches. This can be caused by eating too fast or drinking fizzy drinks.

🎯 Exam Tip: Relate hiccups directly to involuntary spasms of the diaphragm and the abrupt closing of vocal cords.

 

Question 9. What is the need of respiration?
Answer: Respiration is essential because all our body's activities require energy. We get this energy from the food we eat. During respiration, organisms use oxygen to break down complex food molecules, like glucose, into simpler forms. This process releases the energy stored in food, which the body then uses for everything from movement to thinking. Therefore, respiration is vital for producing the energy that sustains life.
In simple words: We need to breathe to get energy. Our body uses oxygen from the air to break down food and make the energy we need for all our actions.

🎯 Exam Tip: The core purpose of respiration is energy production through the breakdown of food using oxygen.

 

Question 10. Why the rate of respiration in aquatic animals is high?
Answer: Aquatic animals have a higher respiration rate compared to land animals because there is much less dissolved oxygen available in water than in air. To extract enough oxygen from their watery environment, aquatic organisms need to move a larger volume of water over their respiratory surfaces more frequently. This increased water flow helps them compensate for the low oxygen concentration, leading to a faster breathing rate.
In simple words: Aquatic animals breathe faster because water has less oxygen than air. They need to move more water over their gills to get enough oxygen.

🎯 Exam Tip: The low concentration of dissolved oxygen in water is the primary reason for faster respiration rates in aquatic animals.

 

Question 11. What is the importance of mucus in the respiratory tract?
Answer: Mucus plays a crucial role in protecting our respiratory tract. Specialized cells called goblet cells in the mucous membrane produce mucus, a sticky, glycoprotein-rich substance. This mucus forms a protective layer that traps harmful particles such as dust, pollen, and microorganisms that we inhale. Tiny hairs (cilia) then sweep this mucus, along with the trapped particles, upwards towards the throat. From there, it is usually swallowed and destroyed by stomach acid, preventing these harmful substances from reaching the lungs.
In simple words: Mucus in your breathing tubes traps dust and germs you breathe in. Small hairs then move this sticky mucus up to your throat, where you swallow it, keeping your lungs clean.

🎯 Exam Tip: Mucus acts as a sticky trap, and cilia as a conveyor belt, protecting the lungs from inhaled foreign particles.

 

Question 12. What is dead space?
Answer: Dead space refers to the volume of inhaled air that occupies the respiratory passages (like the trachea and bronchi) but does not participate in the crucial process of gas exchange within the lungs. This air fills areas where oxygen and carbon dioxide cannot be exchanged with the blood. Essentially, it's air that doesn't contribute to respiration. This volume typically measures about 150 ml in an adult.
In simple words: Dead space is the amount of air that enters your breathing system but does not reach the parts of the lungs where oxygen and carbon dioxide are exchanged. It's about 150 mL of air.

🎯 Exam Tip: Remember that dead space is about the volume of air not involved in actual gas exchange.

 

Question 13. Why should we avoid breathing with our mouths?
Answer: We should generally avoid breathing through our mouths because it can lead to certain physiological effects. One such effect is that mouth breathing might cause the bladder to shrink, which could then create a stronger urge to urinate, especially during the night.
In simple words: Breathing through your mouth can make your bladder smaller, which might make you want to pee more often, even at night.

🎯 Exam Tip: While common reasons for nasal breathing include air filtration and humidification, this answer highlights a less common physiological consequence related to bladder function.

 

IV. Competitive Exam Corner

 

Question 1. Sarojini's father has congestion of the lungs. His doctor advised him to take bed rest and prescribed him an inhaler. What disease is he suffering from? List the symptoms of the disease.
Answer: Based on the symptoms of lung congestion and the doctor's advice for bed rest and an inhaler, Sarojini's father is likely suffering from pneumonia. The common symptoms of pneumonia include:

1. Sputum Production: Coughing up thick mucus or phlegm.
2. Nasal Congestion: A blocked or stuffy nose.
3. Shortness of Breath: Difficulty breathing or feeling like you can't get enough air.
4. Sore Throat: Pain or irritation in the throat.

In simple words: Sarojini's father probably has pneumonia. He would have symptoms like coughing up mucus, a stuffy nose, trouble breathing, and a sore throat.

🎯 Exam Tip: When diagnosing from symptoms, look for a combination that points to a specific condition, and then list all related symptoms clearly.

 

Question 2. A villager who came to the city was affected by severe respiratory illness due to the inhalation of particulate pollutants. Suggest the reason for his illness and how do particulate pollutants affect him.
Answer: The villager is likely suffering from asthma, triggered by a severe dust allergy caused by inhaling particulate pollutants in the city. When he entered the polluted city area, the allergens (pollutants like dust particles) affected his respiratory tracts. This caused an inflammatory response, leading to symptoms like sneezing and coughing. Prolonged exposure to such allergens can worsen the allergy, causing long-term asthma. Particulate pollutants directly irritate and inflame the airways, making breathing difficult and potentially leading to chronic respiratory issues.
In simple words: The villager has asthma caused by a dust allergy from city pollution. The small dust particles irritated his breathing tubes, making them swell and causing him to sneeze and cough.

🎯 Exam Tip: Connect "particulate pollutants" to "allergens" and "inflammatory response," leading to conditions like "asthma."

 

Question 3. Kumar's mother works in a stone grinding factory. Suddenly she faints and taken to the hospital. The doctor notices fibers in the lungs. What kind of disease is she affected with? How can it be rectified?
Answer: Kumar's mother is likely suffering from a disease called silicosis or another type of pulmonary fibrosis. Working in a stone grinding factory means long-term exposure to fine sand particles (silica dust). Inhaling these particles over time causes severe inflammation in the lungs, leading to the formation of fibrous tissue (fibrosis). This fibrosis makes the lungs stiff and unable to function properly, which can cause fainting due to lack of oxygen. To rectify this, she would need to be hospitalized for medical management. Treatment typically involves medications to reduce inflammation and manage symptoms. While some treatments, like Imatinib (mentioned in the source but usually for other forms of fibrosis or cancers, not typical for silicosis directly), are used to fight fibrotic diseases, the primary approach involves supportive care, oxygen therapy, and sometimes lung transplantation in severe cases. Preventing further exposure is also crucial.
In simple words: Kumar's mother has a lung disease called silicosis because she breathed in tiny stone dust for a long time. This dust made her lungs scarred and stiff, making it hard to breathe and causing her to faint. She needs hospital care and medicines to help her lungs.

🎯 Exam Tip: Identify the occupational hazard (stone grinding, sand particles) and connect it to lung fibrosis, which is a key characteristic of silicosis. Note that specific medication might vary.

 

V. Essay Questions

 

Question 1. List the primary functions of the respiratory system?
Answer: The respiratory system performs several essential functions for our body:

1. Gas Exchange: Its main role is to facilitate the exchange of oxygen (\( O_2 \)) and carbon dioxide (\( CO_2 \)) between the air we breathe and our blood. We take in oxygen, and we release carbon dioxide.
2. pH Regulation: It helps maintain a stable acid-base balance (pH) in the body. By controlling how much carbon dioxide is exhaled, it influences blood acidity.
3. Protection: The system acts as a defense against harmful substances. It filters out inhaled pathogens (germs) and pollutants, preventing them from reaching the lungs.
4. Vocalization: It enables normal communication by providing the airflow necessary for the vocal cords to vibrate and produce sound.
5. Heat Removal: Through the process of breathing, it also helps to remove excess heat generated during cellular respiration from the body.

In simple words: The breathing system helps us swap oxygen and carbon dioxide, keeps our body's acid levels balanced, protects us from germs and dirt in the air, lets us talk, and helps remove extra heat from our bodies.

🎯 Exam Tip: When listing functions, aim for a comprehensive overview that covers both primary (gas exchange) and secondary (pH, protection, vocalization, heat) roles.

 

Question 2. Describe the structure of trachea with a diagram.
Answer: The trachea, also known as the windpipe, is a key part of the respiratory system. It is a semi-flexible tube that extends from the larynx (voice box) down into the chest. The trachea is supported by strong, C-shaped rings made of cartilage, which prevent it from collapsing and ensure a constant open airway for air to pass through. At its lower end, within the lungs, the trachea divides into two main tubes: the right and left primary bronchi. These primary bronchi then branch further into smaller secondary and tertiary bronchi. These, in turn, divide repeatedly into even smaller terminal bronchioles and then respiratory bronchioles, eventually leading to the tiny air sacs called alveoli where gas exchange takes place. The C-shaped cartilage plates in the bronchi also help maintain their structure, ensuring they remain open despite changes in air pressure during breathing.

In simple words: The trachea, or windpipe, is a tube with C-shaped cartilage rings that keep it open. It starts from the voice box and splits into two main tubes called bronchi, which then branch into smaller tubes leading to the lungs' air sacs. These rings stop the tubes from collapsing when we breathe.

🎯 Exam Tip: A good diagram of the trachea should clearly show the C-shaped cartilage rings and its bifurcation into the primary bronchi.

 

Question 3. Describe the process of inspiration & expiration with a diagram?
Answer: Breathing involves two main phases: inspiration (inhaling) and expiration (exhaling). These processes rely on changes in the volume of the thoracic cavity and, consequently, the pressure inside the lungs.Inspiration:

1. Muscle Contraction: During inspiration, the diaphragm muscle contracts and flattens, moving downwards. At the same time, the external intercostal muscles between the ribs contract, pulling the ribs and sternum (breastbone) upwards and outwards.
2. Volume Increase: These muscle actions increase the overall volume of the thoracic cavity, particularly along its front-to-back (dorsoventral) and top-to-bottom axes.
3. Pressure Drop: As the thoracic cavity expands, the pressure inside the lungs (pulmonary pressure) drops and becomes lower than the atmospheric pressure outside the body.
4. Air Entry: Because of this pressure difference, fresh air from the outside atmosphere is forced into the air passages and rushes into the lungs until the pressure inside equalizes with the outside pressure.

Expiration:

1. Muscle Relaxation: Expiration is generally a passive process. The diaphragm relaxes and returns to its original dome-shaped position. The external intercostal muscles also relax. For forceful expiration, internal intercostal muscles can contract.
2. Volume Decrease: The relaxation of these muscles causes the rib cage to move downwards and inwards, and the diaphragm rises. This reduces the volume of the thoracic cavity and, consequently, the volume of the lungs.
3. Pressure Increase: As the lung volume decreases, the pressure inside the lungs (intrapulmonary pressure) increases and becomes slightly higher than the atmospheric pressure.
4. Air Expulsion: This higher pressure inside the lungs forces the air out of the lungs and into the atmosphere until the pressures equalize.

In simple words: Breathing in (inspiration) happens when your diaphragm and rib muscles contract, making your chest bigger and sucking air in because the pressure inside drops. Breathing out (expiration) happens when these muscles relax, making your chest smaller and pushing air out because the pressure inside rises.

🎯 Exam Tip: Focus on the role of the diaphragm and intercostal muscles, and how changes in thoracic cavity volume lead to pressure differences that drive airflow.

 

Question 4. Describe the structure of lung with a diagram.
Answer: The lungs are two large, spongy organs vital for breathing, located within the thoracic cavity.

1. Location and Protection: The lungs sit inside the airtight thoracic cavity, which is protected by the vertebral column at the back, the sternum at the front, and the ribs on the sides. Below the lungs is the dome-shaped diaphragm.
2. Pleural Membranes: Each lung is enclosed by a double-layered membrane called the pleura. The space between these layers, known as the pleural cavity, contains a lubricating fluid (pleural fluid). This fluid helps to reduce friction as the lungs expand and contract during breathing.
3. Trachea and Bronchial Tree: Air enters the lungs through the trachea, a semi-flexible tube supported by cartilage rings. The trachea divides into the right and left primary bronchi, which enter the respective lungs. Inside the lungs, these bronchi continue to branch repeatedly into smaller and smaller tubes, forming the bronchial tree, which includes secondary bronchi, tertiary bronchi, and finally tiny bronchioles.
4. Alveoli: At the ends of the smallest bronchioles are clusters of microscopic air sacs called alveoli. These are the primary sites where oxygen and carbon dioxide are exchanged between the air and the blood.

In simple words: Lungs are spongy organs in your chest, protected by ribs and a muscle called the diaphragm. Each lung has two thin coverings with fluid in between to reduce rubbing. Air comes in through a tube (trachea) that branches into smaller tubes (bronchi, bronchioles) leading to tiny air sacs (alveoli) where oxygen enters the blood.

🎯 Exam Tip: A good diagram should show the overall shape of the lungs, their connection to the trachea and bronchi, and the diaphragm below. Ensure to mention the pleural membranes and alveoli.

 

Question 5. Describe the process of transport of oxygen.
Answer: Oxygen is transported throughout the body by the blood in two main ways:

1. Dissolved in Plasma: A small amount, about 3% of the oxygen, dissolves directly into the blood plasma and is carried this way.
2. Bound to Hemoglobin: The majority of oxygen, about 97%, is transported by binding to a protein called hemoglobin, which is found inside red blood cells. When oxygen binds to hemoglobin, it forms oxyhemoglobin. Each hemoglobin molecule can carry up to four molecules of oxygen.

The binding and release of oxygen are influenced by various factors:

• Oxygen Binding (in lungs): In the alveoli of the lungs, where oxygen pressure (\( PO_2 \)) is high, carbon dioxide pressure (\( PCO_2 \)) is low, temperature is low, and hydrogen ion (\( H^+ \)) concentration is low, oxygen readily binds to hemoglobin to form oxyhemoglobin.
• Oxygen Release (in tissues): In the body tissues, where oxygen pressure is low, carbon dioxide pressure is high, temperature is high, and hydrogen ion concentration is high, oxyhemoglobin easily breaks apart, releasing oxygen to the cells.

Efficiently, every 100 ml of oxygenated blood circulating in the body can deliver approximately 5 ml of oxygen to the tissues that need it.
In simple words: Oxygen travels in your blood in two ways: a tiny bit dissolves in the blood, but most of it attaches to a protein called hemoglobin in red blood cells. In the lungs, where there's lots of oxygen, it sticks to hemoglobin. In your body's tissues, where oxygen is needed, it unbinds and goes to the cells. About 5 ml of oxygen is delivered to tissues by every 100 ml of blood.

🎯 Exam Tip: Remember the two forms of transport (dissolved, oxyhemoglobin) and the factors (PO2, PCO2, temperature, pH) that affect oxygen loading and unloading.

 

Question 6. Give the tabulated column of partial pressure of O2 and CO2 in comparison to the gases in the atmosphere.
Answer: The partial pressures of oxygen (\( O_2 \)) and carbon dioxide (\( CO_2 \)) vary significantly across different locations in the body, driving the movement of these gases. The table below illustrates these differences, which are crucial for efficient gas exchange from the atmosphere to the cells. These pressure gradients ensure oxygen is picked up in the lungs and released in tissues, while carbon dioxide moves in the opposite direction.

In simple words: The table shows how much oxygen and carbon dioxide pressure there is in the air, in your lungs, and in your blood and body parts. These different pressures help gases move to where they are needed.

🎯 Exam Tip: Focus on understanding the pressure gradients: \( PO_2 \) is highest in atmospheric air and alveoli, lowest in tissues; \( PCO_2 \) is highest in tissues, lowest in atmospheric air.

 

Question 7. Describe the process of CO2 transport.
Answer: Carbon dioxide (\( CO_2 \)) is transported from the body tissues to the lungs through the blood in three primary ways:

1. Dissolved in Plasma: A small portion, about 7-10% of the \( CO_2 \), dissolves directly into the blood plasma and is transported in this simple form.
2. As Carbaminohemoglobin: Another 20-25% of the \( CO_2 \) binds with the amino groups of hemoglobin within red blood cells, forming a compound called carbaminohemoglobin. This binding is more efficient when oxygen levels are low.
3. As Bicarbonate Ions: The largest amount, about 70% of the \( CO_2 \), is transported as bicarbonate ions (\( HCO_3^- \)). This process occurs mainly within red blood cells:
   • When \( CO_2 \) diffuses from tissues (where \( PCO_2 \) is high due to metabolic activity) into red blood cells, it quickly reacts with water (\( H_2O \)).
   • This reaction is catalyzed by a rapid enzyme called carbonic anhydrase, forming carbonic acid (\( H_2CO_3 \)).
     \( CO_2 + H_2O \xrightarrow{\text{Carbonic anhydrase}} H_2CO_3 \)
   • Carbonic acid then quickly dissociates (breaks down) into hydrogen ions (\( H^+ \)) and bicarbonate ions (\( HCO_3^- \)).
     \( H_2CO_3 \leftrightarrow HCO_3^- + H^+ \)
   • The bicarbonate ions then move into the plasma, and in exchange, chloride ions move into the red blood cells to maintain electrical balance (chloride shift).

Overall, this efficient system ensures that every 100 ml of deoxygenated blood can deliver approximately 4 ml of \( CO_2 \) to the alveoli in the lungs for exhalation.
In simple words: Carbon dioxide travels in your blood in three main ways: a little bit dissolves in the blood, some attaches to hemoglobin (forming carbaminohemoglobin), but most is carried as bicarbonate ions. This happens quickly inside red blood cells where carbon dioxide mixes with water to become carbonic acid, which then splits into bicarbonate and hydrogen ions. About 4 ml of carbon dioxide is carried to your lungs by every 100 ml of deoxygenated blood.

🎯 Exam Tip: Remember the three forms of \( CO_2 \) transport and especially the crucial role of carbonic anhydrase in forming bicarbonate ions, which is the major transport mechanism.

 

Question 8. Describe the process of regulation of respiration.
Answer:

• The medulla oblongata acts as the main control center for breathing. This part of the brain makes sure we breathe without thinking.
• The pons varoli also has a special center that helps control the rhythm of our breathing. It fine-tunes how quickly and deeply we breathe.
• There is a sensitive area near the rhythm center that reacts to levels of \( \text{CO}_2 \) and \( \text{H}^+ \) (hydrogen ions). When these levels are high, it signals the body to breathe more.
• Excess \( \text{H}^+ \) ions are removed from the body through the breathing process.
• Certain sensors in the aortic arch and carotid artery also send signals to the brain's breathing center to help adjust our breath as needed.

In simple words: Our brain controls how we breathe using special centers. These centers adjust breathing speed and depth based on things like carbon dioxide levels in the blood, ensuring we get enough oxygen and remove waste gases.

🎯 Exam Tip: Remember the main brain areas (medulla oblongata, pons varoli) and chemical factors (\( \text{CO}_2 \) and \( \text{H}^+ \)) involved in regulating breathing rate.

 

Question 9. Write an essay on respiratory disorders.
Answer: The respiratory system can be affected by various environmental, occupational, and personal factors, leading to several disorders. These conditions often involve inflammation or damage to the respiratory pathways, making breathing difficult.
Asthma: This is a common disorder where the airways (bronchi and bronchioles) become narrow and inflamed, causing difficulty in breathing. Allergens like dust, pollen, certain foods, or even drugs can trigger asthma attacks.
Emphysema: This is a chronic lung disease characterized by long-term breathlessness. It happens when the thin walls of the alveoli (air sacs) gradually break down, reducing the total surface area for gas exchange. Cigarette smoking is a major cause, as it damages the alveolar walls.
Bronchitis: This involves inflammation of the bronchi, the main air passages to the lungs. It often leads to mucous buildup and a persistent cough. Pollution and cigarette smoke are common causes.
Pneumonia: This is an inflammation of the lungs, usually caused by infection from bacteria or viruses. Symptoms include sputum production, nasal congestion, shortness of breath, and a sore throat. In severe cases, the alveoli fill with fluid or pus, making breathing very difficult.
Tuberculosis: Caused by the bacterium Mycobacterium tuberculosis, this infection mainly affects the lungs but can also spread to bones. It can lead to fluid accumulation between the lungs and the chest wall, which is a serious complication. Recognizing symptoms early can help in effective management and treatment.
In simple words: Respiratory disorders are lung problems that make it hard to breathe. They can be caused by allergies, smoking, or infections. Asthma narrows airways, emphysema damages air sacs, bronchitis inflames tubes, pneumonia fills lungs with fluid, and tuberculosis is a serious infection.

🎯 Exam Tip: When describing respiratory disorders, always state the cause, main symptoms, and the part of the respiratory system affected for each condition.

 

Question 10. List the ill effects of smoking.
Answer:

• Smoking makes the heart beat faster, increasing the heart rate.
• It narrows blood vessels, which leads to higher blood pressure and can cause coronary heart diseases.
• Smoking harms the airways and alveoli (air sacs) in the lungs, leading to diseases like emphysema and chronic bronchitis. The tar from tobacco also damages the gas exchange system.
• Carbon monoxide from smoke reduces the amount of oxygen that blood can carry.
• Smoking is linked to various cancers, including lung, stomach, pancreas, and bladder cancer.
• It can also lower sperm count in men, affecting fertility. It's clear that smoking has many serious health consequences.

In simple words: Smoking makes your heart work harder, raises blood pressure, damages your lungs, reduces oxygen in your blood, and can cause many types of cancer. It is very harmful to overall health.

🎯 Exam Tip: Focus on listing at least five distinct negative impacts of smoking on different body systems (cardiovascular, respiratory, reproductive, immune) to score well.

 

Question 11. Tabulate the organism. respiratory organs and the
Answer: The table below shows different organisms and their primary respiratory organs.

In simple words: Different animals breathe in different ways. Some use their skin or body surface, while others have special organs like gills or lungs to take in oxygen from their environment.

🎯 Exam Tip: When listing respiratory organs, be precise with the animal group and ensure the organ matches its primary breathing method (e.g., gills for aquatic, lungs for terrestrial).

 

Question 12. What are the steps involved in the respiratory process?
Answer: The respiratory process involves several key steps to ensure gas exchange in the body:

1. Air is exchanged between the atmosphere and the lungs. This is what we call breathing.
2. Oxygen (\( \text{O}_2 \)) and carbon dioxide (\( \text{CO}_2 \)) are exchanged between the lungs and the blood. Oxygen enters the blood, and carbon dioxide leaves it.
3. The blood then transports both \( \text{O}_2 \) and \( \text{CO}_2 \) throughout the body.
4. Gas exchange also happens between the blood and the body cells. Oxygen moves into the cells, and carbon dioxide moves out.
5. Finally, cells take in \( \text{O}_2 \) for various activities and release \( \text{CO}_2 \) as a waste product.

In simple words: Respiration means breathing in air, getting oxygen into the blood from the lungs, carrying it to cells, and then getting carbon dioxide out of cells and breathing it out.

🎯 Exam Tip: Remember to differentiate between external respiration (atmosphere to lungs, lungs to blood) and internal respiration (blood to cells, cells to blood).

 

Question 13. Tabulate the disorders of respiratory system.
Answer: Here is a table listing common respiratory disorders and their associated symptoms.

In simple words: This table shows different breathing problems and what happens in each one. For example, bronchitis means your breathing tubes are swollen, and asthma makes airways narrow with extra mucus.

🎯 Exam Tip: For tabulation questions, clearly list the disorder and a concise, distinct symptom or characteristic for each one.

 

Question 14. List the problems in oxygen transport.
Answer: Problems in oxygen transport can arise in various situations, especially with changes in altitude or pressure:

• When a person goes to high places (above 8000 feet), the air pressure and oxygen levels are lower. This makes it harder for oxygen (\( \text{O}_2 \)) to attach to hemoglobin in the blood.
• This difficulty in oxygen binding can lead to symptoms like headache, shortness of breath, nausea, and dizziness, collectively known as acute mountain sickness.
• To adjust to high altitudes over time, the kidneys produce more of a hormone called erythropoietin. This hormone stimulates the bone marrow to make more red blood cells, which helps carry more oxygen.
• When a person dives deep into the sea, the water pressure increases, which causes the lungs to decrease in volume. This also increases the partial pressure of gases inside the lungs, helping oxygen go into the blood.
• However, increased pressure can also push nitrogen gas into the blood. If a diver comes up to the surface too quickly, this dissolved nitrogen can form bubbles in the blood, causing a condition called 'bends' or decompression sickness. These bubbles can cause joint and muscle pain and can block blood flow, leading to serious neurological problems.

In simple words: Oxygen transport can be difficult in high mountains because there's less oxygen in the air. Deep-sea diving can also cause problems, like 'bends', if nitrogen gas gets trapped in the blood when a diver comes up too fast.

🎯 Exam Tip: For questions about oxygen transport, consider both high-altitude effects (reduced \( \text{O}_2 \) binding, AMS, erythropoietin response) and deep-sea diving effects (nitrogen narcosis, decompression sickness).

 

Question 15. List the toxic substances present in tobacco. What are the ill-effects of smoking.
Answer:
(a) Toxic substances present in tobacco: Tobacco contains many harmful substances, including nicotine, tar, carbon monoxide, ammonia, arsenic, and sulfur dioxide.
(b) Ill effects of smoking:

• Carbon monoxide and nicotine severely damage the heart and blood vessel system.
• Tar harms the system responsible for gas exchange in the lungs.
• Nicotine makes the heart beat faster and narrows the blood vessels, resulting in high blood pressure and coronary heart diseases.
• Carbon monoxide reduces the amount of oxygen that the blood can carry.
• Smoking leads to various cancers, such as lung, stomach, pancreas, and bladder cancer.
• It also decreases sperm count in men.

In simple words: Tobacco has bad chemicals like nicotine and tar. Smoking these harms your heart and blood vessels, damages your lungs, causes cancer, and can make men have fewer sperm.

🎯 Exam Tip: When listing the toxic substances in tobacco, include nicotine, tar, and carbon monoxide. For ill effects, describe how smoking impacts the cardiovascular and respiratory systems.

 

Question 16. What is meant by chronic obstructive pulmonary disease?
Answer:

• Smoking is a major cause of lung diseases because it damages the airways and alveoli (air sacs). This damage can lead to emphysema and chronic bronchitis.
• These two conditions, emphysema and chronic bronchitis, along with asthma, are grouped together and called Chronic Obstructive Pulmonary Disease (COPD). COPD makes it very hard to breathe normally.
• When someone smokes, about 85% of the smoke is inhaled by them. The people around them who breathe in the smoke indirectly are called passive smokers, and they are also affected by these harmful substances. Protecting your lungs from smoke is crucial for preventing COPD.

In simple words: Chronic Obstructive Pulmonary Disease (COPD) is a group of long-term lung problems, like emphysema and chronic bronchitis, mostly caused by smoking. It makes breathing difficult because the airways and air sacs get damaged.

🎯 Exam Tip: Define COPD as a group of diseases (emphysema, chronic bronchitis, asthma) and highlight smoking as the primary risk factor, explaining its impact on airways and alveoli.

 

Question 17. List the events in inspiration and expiration.
Answer: Here is a comparison of the events that occur during inspiration (breathing in) and expiration (breathing out).

In simple words: When we breathe in, our brain sends signals, muscles work, the chest expands, and air rushes into the lungs. When we breathe out, muscles relax, the chest gets smaller, and air is pushed out.

🎯 Exam Tip: Clearly distinguish between inspiration (active process, muscles contract, volume increases, pressure drops) and expiration (passive process, muscles relax, volume decreases, pressure rises) in your explanation.

 

Question 18. Describe the relationship between partial pressure of O2 and the nature of O2 dissolving the haemoglobin.
Answer: The relationship between the partial pressure of oxygen (\( \text{O}_2 \)) and how \( \text{O}_2 \) binds to hemoglobin is crucial for oxygen transport in the body.

1. Oxygen is carried in the blood in two main ways: a small amount (about 3%) is dissolved in the plasma, and the majority (about 97%) binds to hemoglobin inside red blood cells to form oxyhemoglobin.
2. Each hemoglobin molecule can carry up to four molecules of \( \text{O}_2 \).
3. In the alveoli (air sacs in the lungs), there is a high partial pressure of \( \text{O}_2 \), low partial pressure of \( \text{CO}_2 \), low temperature, and less \( \text{H}^+ \) (which means higher pH). These conditions are perfect for \( \text{O}_2 \) to bind strongly to hemoglobin and form oxyhemoglobin.
4. Conversely, in body tissues, the conditions are different: low partial pressure of \( \text{O}_2 \), high partial pressure of \( \text{CO}_2 \), high temperature, and high \( \text{H}^+ \) (lower pH). These factors make it easier for \( \text{O}_2 \) to detach from hemoglobin (dissociate) and move into the tissues. This process ensures that oxygen is delivered where it's needed most for cellular functions.
5. A graph showing the percentage saturation of hemoglobin with \( \text{O}_2 \) against the partial pressure of \( \text{O}_2 \) creates a specific S-shaped curve called the oxygen dissociation curve. This curve shows that hemoglobin picks up oxygen well when there's a lot of it (like in the lungs) and releases it easily when there's less oxygen (like in the tissues). The curve is steep between 10 and 50 mm Hg and then flattens between 70 and 100 mm Hg.
6. Under normal body conditions, every 100 ml of oxygen-rich blood can deliver about 5 ml of \( \text{O}_2 \) to the tissues.

In simple words: Oxygen travels in blood mostly attached to hemoglobin. In the lungs, where there's lots of oxygen, it sticks to hemoglobin. In body parts that need oxygen, it lets go of hemoglobin. This "sticking and letting go" depends on how much oxygen is around, which is shown by an S-shaped graph.

🎯 Exam Tip: When explaining oxygen-hemoglobin dissociation, focus on the opposing conditions in the lungs (high \( \text{PO}_2 \), low \( \text{PCO}_2 \)) versus tissues (low \( \text{PO}_2 \), high \( \text{PCO}_2 \)) that favor binding and release, respectively.

 

Question 19. List the PO2 and PCO2 during inspiration expiration and in lungs and blood vessels.
Answer: The table below shows the partial pressures of oxygen (\( \text{PO}_2 \)) and carbon dioxide (\( \text{PCO}_2 \)) in different locations during breathing and within the circulatory system.

In simple words: This table shows how much oxygen and carbon dioxide pressure is in different parts of your body, like when you breathe in and out, and in your lungs and blood vessels. It helps to understand how gases move around.

🎯 Exam Tip: Pay close attention to the small differences in partial pressures that drive gas exchange, particularly between alveoli and pulmonary capillaries for both \( \text{O}_2 \) and \( \text{CO}_2 \).