GSEB Class 11 Biology Solutions Chapter 18 Body Fluids and Circulation

 

Question 1. Xante the component of the formed elements in the blood and mention one major function of each of them.
Answer: Erythrocytes, leucocytes, and platelets are collectively called the formed components of the blood. Erythrocytes are known as red blood cells (RBCs). These cells play a crucial part in the movement of respiratory gases. Leucocytes are also called white blood cells (WBCs). There are two main kinds of WBCs: granulocytes and agranulocytes. Neutrophils, eosinophils, and basophils are various sorts of granulocytes, while lymphocytes and monocytes are the agranulocytes.
Neutrophils and monocytes are phagocytic cells that eliminate foreign organisms entering the body. Basophils secrete substances like histamine, serotonin, heparin, etc., and are involved in allergic reactions. Lymphocytes are accountable for the immune reactions of the body. Platelets, also known as thrombocytes, are cell fragments produced from megakaryocytes. Platelets are essential for the clotting or coagulation of blood.
In simple words: The main parts of blood are red blood cells, white blood cells, and platelets. Red blood cells carry oxygen. White blood cells fight germs and help with immunity. Platelets make blood clot.

Exam Tip: When asked to name components and their functions, list each component clearly and provide one distinct, major function for each to ensure full marks.

 

Question 2. What is the importance of plasma proteins?
Answer: Fibrinogen, globulins, and albumins are the main plasma proteins.
1. Fibrinogens are required for the clotting or coagulation of blood.
2. Globulins primarily take part in the body's defense mechanisms.
3. The albumins help in maintaining osmotic balance.
In simple words: Plasma proteins like fibrinogen help blood clot, globulins protect the body from illness, and albumins keep the body's fluid balance correct.

Exam Tip: Remember the three major plasma proteins and their distinct roles: Fibrinogen for clotting, Globulins for immunity, and Albumins for osmotic balance.

 

Question 3. Match column I with column II:
Column I
(i) Ecosinophils
(ii) RBC
(iii) AB Group
(iv) Platelets
(v) Systole
Column II
(a) Coagulation
(b) Universal Recipient
(c) Resist Infections
(d) Contraction of Heart
(e) Gas transport
Answer:
1. (c) Resist Infections
2. (e) Gas transport
3. (b) Universal Recipient
4. (a) Coagulation
5. (d) Contraction of Heart
In simple words: Eosinophils help fight infections. Red blood cells move gases. AB blood type can get blood from anyone. Platelets make blood clot. Systole is when the heart squeezes.

Exam Tip: For matching questions, connect each item from Column I to its correct function or description in Column II, ensuring all pairs are accurately linked.

 

Question 4. Why do we consider blood as a connective tissue?
Answer: Connective tissue usually takes part in structure and support and is formed from the mesoderm. Blood is considered a connective tissue because:
1. It has the same origin (mesodermal) as other connective tissues.
2. Blood connects the body systems together, bringing necessary oxygen, nutrients, hormones, and other vital molecules and getting rid of waste.
In simple words: Blood is a connective tissue because it comes from the same cell layer as other such tissues. It also links all body parts by moving important substances and taking away waste.

Exam Tip: Highlight the shared embryonic origin (mesodermal) and its transport function as the key reasons why blood is classified as a connective tissue.

 

Question 5. What is the difference between lymph and blood?
Answer: Differences between the lymph and blood
Lymph:
Lymph is a transparent fluid containing specific lymphocytes that are accountable for the body's immune reactions. Lymph is also a significant carrier for nutrients, hormones, etc. Fats are taken in through lymph in the lacteals present in the intestinal villi.
Blood:
Blood is made up of a liquid medium called plasma, in which three kinds of blood cells float: red blood cells, white blood cells, and blood platelets. Blood cells are produced in the bone marrow.
In simple words: Lymph is a clear fluid with special white blood cells for immunity and carries fats. Blood is a red fluid with plasma, red blood cells (for oxygen), white blood cells (for fighting sickness), and platelets (for clotting), all made in bone marrow.

Exam Tip: Clearly distinguish between lymph and blood based on color, primary cell types, composition, and main functions like immunity vs. general transport and oxygenation.

 

Question 6. What is meant by double circulation? What is its significance?
Answer: Double circulation means the separate systems of pulmonary circulation and systemic circulation. The deoxygenated blood pumped into the pulmonary artery is sent to the lungs, from where the oxygenated blood is carried by the pulmonary veins into the left atrium. This pathway is called pulmonary circulation.
The oxygenated blood entering the aorta is carried by arteries and capillaries to the tissues, from where the deoxygenated blood is collected by a system of venules, veins, and vena cava and emptied into the right atrium. This is known as systemic circulation.
The systemic circulation is responsible for giving nutrients, \( \text{O}_2 \), and other necessary substances to the tissues and taking away \( \text{CO}_2 \) and other harmful substances for elimination.
In simple words: Double circulation means blood goes through the heart twice in one complete circuit. First, it goes to the lungs to get oxygen (pulmonary circulation). Then, it goes to the rest of the body to deliver oxygen and nutrients, and collect waste (systemic circulation). This makes sure oxygen-rich blood reaches the body effectively.

Exam Tip: When defining double circulation, explain both pulmonary and systemic circulation clearly, and emphasize that it ensures efficient separation of oxygenated and deoxygenated blood.

 

Question 7. Write the differences between:
1. Blood and lymph
2. The open and closed system of circulation
3. Systole and diastole
4. P-wave and T-wave

Answer:
(1) Difference between the blood and lymph
Lymph:
Lymph is a colorless fluid containing specific lymphocytes that are accountable for the body's immune reactions. Lymph is also an important carrier for nutrients, hormones, etc. Fats are absorbed through lymph in the lacteals found in the intestinal villi.
Blood:
Blood is made up of a fluid medium called plasma, in which three kinds of blood cells float: red blood cells, white blood cells, and blood platelets. Blood cells are manufactured in the bone marrow.

(2) Difference between Open circulatory system and Closed circulatory system
Open circulatory system:
The open circulatory system is found in arthropods and mollusks, where blood pumped by the heart goes through large vessels into open spaces or body cavities called sinuses.
Closed circulatory system:
Annelids and chordates have a closed circulatory system in which the blood pumped by the heart is always moved through a closed network of blood vessels. This pattern is considered more beneficial as the flow of fluid can be more precisely managed.

(3) Difference between Systole and Diastole
Systole:
Ventricular systole raises the ventricular pressure, causing the closure of the tricuspid and bicuspid valves due to the attempted backflow of blood into the atria. As ventricular pressure rises further, the semilunar valve guarding the pulmonary artery (right side) and the aorta (left side) is forced open, allowing blood in the ventricles to flow through these vessels into the circulatory pathways. Systolic pressure is higher and happens during ventricular contraction.
Diastole:
The ventricles now relax (ventricular diastole), and the ventricular pressure drops, causing the closure of semilunar valves which stop blood from flowing back into the ventricles. As the ventricular pressure keeps falling, the tricuspid and bicuspid valves are pushed open by the pressure in the atria, caused by blood being emptied into them by the veins. Diastolic pressure is lower and happens during ventricular expansion.

(4) Difference between P-wave and T-wave
P-wave:
The P-wave shows the electrical excitation (or depolarization) of the atria, which leads to the contraction of both atria.
T-wave:
The T-wave shows the return of the ventricles from an excited to a normal state (repolarization). The end of the T-wave marks the end of the systole.
In simple words: Lymph and blood differ in composition and role. Open circulation sends blood to open spaces, while closed circulation keeps it in vessels. Systole is heart contraction, diastole is relaxation. P-wave shows atrial electrical activity, and T-wave shows ventricular relaxation.

Exam Tip: For differentiation questions, use clear, concise comparisons for each pair. Ensure you mention key characteristics for both sides of the comparison to earn full credit.

 

Question 8. Describe the evolutionary change in the pattern of heart among the vertebrates.
Answer: All vertebrates have a muscular, chambered heart. Fish have a two-chambered heart with one atrium and one ventricle. Amphibians and reptiles (except crocodiles) have a three-chambered heart with two atria and a single ventricle, while crocodiles, birds, and mammals have a four-chambered heart with two atria and two ventricles. In fish, the heart pumps out deoxygenated blood, which then gets oxygenated by the gills and goes to the body parts. From there, deoxygenated blood returns to the heart (this is single circulation).
In amphibians and reptiles, the left atrium gets oxygenated blood from the gills, lungs, or skin, and the right atrium gets deoxygenated blood from other body parts. However, these two types of blood mix in the single ventricle, which then pumps out mixed blood (this is incomplete double circulation). In birds and mammals, oxygenated and deoxygenated blood goes to the left and right atria, respectively, and then passes to the ventricles on the same sides. The ventricles pump out blood without any mixing, meaning two separate circulatory paths are present in these animals, which is known as double circulation.
In simple words: Hearts in vertebrates changed over time. Fish have two chambers. Amphibians and most reptiles have three, leading to some blood mixing. Crocodiles, birds, and mammals have four chambers, which completely separates clean and used blood, making circulation more efficient.

Exam Tip: Trace the evolution of the heart by focusing on the number of chambers and the efficiency of blood separation (single, incomplete double, double circulation) across different vertebrate groups.

 

Question 9. Why do we call our heart myogenic?
Answer: We call our heart myogenic because its normal functions are regulated intrinsically, meaning it is self-regulated by specialized muscles (nodal tissue). A special neural center in the medulla oblongata can change cardiac function through the autonomic nervous system (ANS). Neural signals from the sympathetic system affect ventricular contraction and thus cardiac output. On the other hand, parasympathetic neural signals (another part of ANS) slow down the heart rate, the speed of action potential conduction, and consequently the cardiac output. Adrenal medullary hormones can also raise cardiac output.
In simple words: Our heart is called myogenic because it can beat on its own, without external nerves, due to special muscle tissue. While nerves can adjust its beat, the heart itself starts the rhythm.

Exam Tip: The key to explaining "myogenic" is to state that the heart's contraction originates within the cardiac muscle tissue itself (nodal tissue), independent of external nervous stimulation.

 

Question 10. The Sinoatrial node is called the pacemaker of our heart. Why?
Answer: The sinoatrial node (SAN) can produce the highest number of action potentials, about 70-75 per minute, and is accountable for initiating and maintaining the heart's rhythmic contractile activity. Therefore, it is called the pacemaker, meaning our heart typically beats 70-75 times per minute (an average of 72 beats/minute). The entire heart is made of cardiac muscle. The walls of the ventricles are much thicker than those of the atria. A specialized cardiac muscle tissue, known as nodal tissue, is also found in the heart (Fig 18.2). A patch of this tissue is located in the upper right corner of the right atrium and is called the sino-atrial node (SAN).
In simple words: The Sinoatrial node is the heart's pacemaker because it starts the electrical signals that make the heart beat regularly, about 70-75 times a minute. It sets the heart's natural rhythm.

Exam Tip: Emphasize the SAN's ability to generate the maximum number of action potentials (impulses) per minute and its role in initiating and regulating the heartbeat rhythm.

 

Question 11. What is the significance of the atrioventricular node and atrioventricular bundle in the functioning of the heart?
Answer: The heartbeat impulse, started by the Sinoatrial node, is picked up by the Atrioventricular node, and the action potential is sent to the ventricular side. From the AV node, the heartbeat is then transmitted to the AV bundle (Bundle of HiS), which moves it through the entire ventricular muscle.
In simple words: The atrioventricular node (AV node) receives the heart's electrical signal from the top chambers and passes it to the atrioventricular bundle (Bundle of His), which then spreads it to the bottom chambers, making them contract. This ensures proper coordination between the heart's upper and lower parts.

Exam Tip: Focus on the AV node's role in delaying and transmitting impulses from atria to ventricles, and the AV bundle's role in distributing these impulses rapidly to ensure synchronized ventricular contraction.

 

Question 12. Define cardiac cycle and cardiac output.
Answer: This sequence of events in the heart, which repeats in a cycle, is called the cardiac cycle, and it includes the systole and diastole of both the atria and ventricles. The heart beats 72 times per minute, meaning that many cardiac cycles are completed per minute. From this, it can be calculated that the length of one cardiac cycle is 0.8 seconds. During a cardiac cycle, each ventricle pumps out approximately 70ml of blood, which is called the stroke volume. The stroke volume multiplied by the heart rate (number of beats per minute) gives the cardiac output.
Therefore, cardiac output can be defined as the volume of blood pumped out by each ventricle per minute, and it averages 5000ml or 5 liters in a healthy person. We have the ability to change the stroke volume as well as the heart rate, and by doing so, we can alter the cardiac output. For instance, the cardiac output of an athlete will be much higher than that of an average person.
In simple words: A cardiac cycle is one full heartbeat, including squeezing and relaxing. Cardiac output is how much blood the heart pumps out each minute, calculated by multiplying how much blood is pumped per beat (stroke volume) by the number of beats per minute.

Exam Tip: Clearly define both cardiac cycle (sequential events of a single heartbeat) and cardiac output (volume of blood pumped per minute), and state the formula for cardiac output.

 

Question 13. Explain heart sounds.
Answer: During each cardiac cycle, two main sounds, 'lub' and 'dub,' are heard. The first heart sound (lub) is linked to the closure of the tricuspid and bicuspid valves, lasting for 0.16–0.9 seconds. The second heart sound (dub) is linked to the closure of the semilunar valves and lasts for 0.10 seconds.
In simple words: The heart makes two main sounds: "lub" and "dub." "Lub" happens when the valves between the atria and ventricles close. "Dub" happens when the valves leaving the heart (semilunar valves) close.

Exam Tip: Remember the two main heart sounds ('lub' and 'dub') and associate each with the specific valve closures (tricuspid/bicuspid for lub, semilunar for dub).

 

Question 14. Draw a standard ECG and explain the different segments in it.
Answer: Diagrammatic presentation of a standard ECG:

Each peak in the ECG is identified with a letter from P to T, which corresponds to a specific electrical activity of the heart. The P-wave represents the electrical excitation (or depolarization) of the atria, which causes both atria to contract.
The QRS complex represents the depolarization of the ventricles, which starts the ventricular contraction. The contraction begins shortly after Q and marks the beginning of the systole.
The T-wave represents the return of the ventricles from an excited state to a normal state (repolarization). The end of the T-wave marks the end of the systole.
In simple words: An ECG shows the heart's electrical activity. The P-wave is when the top chambers contract. The QRS complex is when the bottom chambers contract. The T-wave is when the bottom chambers relax.

Exam Tip: When drawing and explaining an ECG, clearly label the P-wave, QRS complex, and T-wave, and describe the specific cardiac event (atrial depolarization, ventricular depolarization, ventricular repolarization) each represents.