RBSE Solutions Class 12 Biology Chapter 29 Man-Chemical Coordination

Endocrine Gland	Exocrine Gland
They are ductless	They have ducts
Their secretions are called hormones	Not called
Example: Pituitary	Example: Liver

Endocrine glands release hormones directly into the bloodstream for distant targets, while exocrine glands use ducts to secrete substances locally or externally. This difference in delivery mechanism is fundamental.
In simple words: Endocrine glands release their chemicals directly into your blood, like the pituitary gland. Exocrine glands use small tubes, called ducts, to send their chemicals to specific places, like sweat glands or the liver.

🎯 Exam Tip: Focus on the presence or absence of ducts as the primary distinguishing feature between endocrine and exocrine glands.

 

Question 2. Explain the functions of thyroxin hormone.
Answer: Functions of Thyroxine hormone:

• It increases oxidative metabolism, which means it helps the body produce more energy faster. This makes our body functions more efficient.
• It helps in making proteins and also in gluconeogenesis (making new sugar). It increases body temperature and helps nerves work well.
• It helps the small intestine absorb glucose and increases how much oxygen the body uses. It also boosts the basic metabolic rate (BMR).
• It makes the heartbeat faster.
• It plays a big part in changing tadpoles into frogs (metamorphosis). This shows its important role in development.
• It helps cold-blooded animals control how much water is in their bodies (osmotic regulation). It also makes the activity of neurosecretion adrenaline and nor-adrenaline higher.

In simple words: Thyroxine hormone controls how fast your body uses energy and helps with growth. It affects many things, from your heartbeat to how tadpoles grow into frogs.

🎯 Exam Tip: When listing functions of a hormone, group related actions together (e.g., metabolism, growth, development) to ensure completeness and clarity.

 

Question 4. Write a source of thyroxin hormone.
Answer: Cells of thyroid follicles. These cells are specialized to produce and store thyroid hormones.
In simple words: Thyroxin hormone is made by special cells found in the small sacs, or follicles, inside the thyroid gland.

🎯 Exam Tip: Always identify the specific gland and the particular cells or structures within it that produce a given hormone.

 

Question 5. Write the name of releasing and inhibiting hormones secreted by the hypothalamus.
Answer:

The hypothalamus produces a variety of releasing and inhibiting hormones that regulate the anterior pituitary gland, thereby controlling many other endocrine functions. These hormones ensure precise control over the body's hormonal balance.
In simple words: The hypothalamus in your brain makes special hormones that either tell other glands to release their hormones (releasing hormones) or stop releasing them (inhibiting hormones). This helps to control the body's overall hormone system.

🎯 Exam Tip: Understanding the feedback loop between the hypothalamus, pituitary, and other glands is key to comprehending endocrine regulation.

 

Diseases:

1. Addison's disease: It is caused due to deficiency of mineralocorticoids. Symptoms: Reduced hunger, vomiting, reduced BMR & body temperature, dehydration & bronzing of the skin.
2. Conn's disease: It is caused due to excess secretion of mineralocorticoids. Symptoms: Muscle weakness, high BP, malfunctioning of kidneys etc.
3. Cushing's disease: It is caused due to hypersecretion of corticosteroids. It is caused due to hypersecretion of corticosteroids which is due to excess of ACTH. Symptoms: Virilism, oedema, hyperglycaemia etc. In virilism, opposite secondary sexual characters appear and it is more common in women. The virilism in a female is also called as hirsutism.

These conditions illustrate how critical the balance of adrenal hormones is for overall health, with both too little and too much causing serious symptoms.

 

Question 7. "Goiter disease frequently occurs in the persons living on the hills". Explain with reasons.
Answer: The drinking water at high altitude is without dissolved iodine. Moreover, there is a lack of aquatic food at hills which is a good source of iodine. This explains why goitre is common in these regions.
In simple words: People living in hilly areas often get goitre because their drinking water does not have iodine. Also, they don't eat much seafood, which is a good natural source of iodine.

🎯 Exam Tip: Always link environmental factors (like altitude or diet) to their direct biological consequences when explaining health conditions.

 

Question 8. Write names of hormones secreted by Adenohypophysis.
Answer:

• Growth Hormone
• Melanophore Stimulating Hormone

The adenohypophysis, or anterior pituitary, produces and secretes several vital hormones that regulate other endocrine glands and various body functions.
In simple words: The adenohypophysis, which is the front part of the pituitary gland, makes hormones like Growth Hormone and Melanophore Stimulating Hormone. These hormones help with growth and skin color, among other things.

🎯 Exam Tip: Remember that the anterior pituitary is responsible for producing and releasing many trophic hormones that control other glands, making it a "master gland."

 

Question 9. If thyroidectomy performs in man, what will happen?
Answer: It will cause hypothyroidism in the body which in turn will result in cretinism or Goitre or Myxaedena. Removing the thyroid gland eliminates the source of essential thyroid hormones, leading to severe metabolic disruption.
In simple words: If a man has his thyroid gland removed (thyroidectomy), his body will not make enough thyroid hormone. This can lead to health problems like cretinism (in children), goitre, or myxedema (in adults).

🎯 Exam Tip: Understand that surgical removal of an endocrine gland (like thyroidectomy) directly leads to a deficiency of the hormones produced by that gland, with specific health consequences.

 

Question 10. Write symptoms of Myxedema disease.
Answer: Puffiness of skin on face & hands, Reduced blood pressure, BMR & heartbeats, increased obesity, Rough & dry skin, Loss of Hair etc. Myxedema is a severe form of hypothyroidism that affects multiple body systems.
In simple words: Myxedema symptoms include puffy skin on the face and hands, low blood pressure, a slower heartbeat, weight gain, dry and rough skin, and hair loss. It happens when the body does not have enough thyroid hormone.

🎯 Exam Tip: When describing disease symptoms, categorize them by body system (e.g., skin, cardiovascular, metabolic) for a more structured and comprehensive answer.

 

Rbse Class 12 Biology Chapter 29 Essay Type Questions

 

Question 1. Draw a labelled diagram of the pituitary gland and Describe the hormones secreted by Neurohypophysis.
Answer:Hormones of Neurohypophysis:

• The pars nervosa stores & releases two hormones which are secreted by supraoptic nucleus & paraventricular nucleus viz., oxytocin & vasopressin respectively. These hormones are actually made in the hypothalamus but stored in the neurohypophysis.
• Both the oxytocin & vasopressin are octapeptide & each has 8 amino acids.

1. Oxytocin:

• It is found only in females & it is also called as Pitocin.
• It helps in parturition by stimulating contraction of the uterine muscles.
• It also helps in the release of the milk from the mammary glands after parturition.

2. Vasopressin:

• It is also called antidiuretic hormone (ADH) because it helps reduce urine production.
• It increases water reabsorption in the kidneys, helping the body retain water.
• Vasopressin also plays a role in regulating blood pressure by constricting blood vessels.

In simple words: The neurohypophysis (back part of the pituitary gland) stores and releases two hormones: oxytocin and vasopressin. Oxytocin helps with childbirth and milk release in women. Vasopressin helps the body keep water and controls blood pressure.

🎯 Exam Tip: Remember that the neurohypophysis stores hormones produced by the hypothalamus, unlike the adenohypophysis which produces its own hormones.

 

Question 2. Describe in brief the hormones secreted by the thyroid gland and diseases caused by their irregular secretions.
Answer: The thyroid gland secretes two hormones.
1. Thyroxine
2. Calcitonin

Disorders Related to Thyroxine Hormone:
(1) Hypothyroidism:

• Hypothyroidism, or low thyroid hormone, happens if the thyroid gland does not work well or if there is not enough iodine in the diet. This is a common cause of thyroid issues.
• and Basal metabolic rate (BMR) are below normal. Such individuals may be sterile.

2. Myxedema:

• It occurs in adults due to deficiency of thyroxine. There is puffiness of skin on the face and hands.
• The person becomes dull, lacks intelligence and alertness, and has poor memory.
• Blood pressure, heart rate, and BMR are below normal. The skin becomes yellowish, and reproductive ability decreases. It can be cured by treating the patient with thyroxin tablets orally.

3. Goitre:

• This disease happens because there is not enough iodine in the food. The thyroid gland gets bigger, and the patient's neck swells up. There is less thyroxine made because iodine, which is needed for it, is not available.
• This disease is more common in people living in high places because their water does not have enough iodine.

4. Hashimoto's Disease:

• It is caused by the body making antibodies against the medicines given to cure diseases due to low thyroid hormone. These antibodies destroy the thyroid gland. It is also called as Suicide of thyroid gland. It is an autoimmune disorder where the body attacks its own cells.

(2) Hyperthyroidism:

• Increased activity of the thyroid gland leads to too much hormone in the body. This speeds up metabolic activities, changes the heartbeat rate, affects behavior, and causes more sweating. It also makes hands and feet shake. Too much thyroxine results in the following diseases.

1. Exophthalmic Goiter:

• The gland releases too much hormone, causing swelling in the neck. In this disease, goitre comes with bulging eyeballs, making the person's vision look scary and eyes look staring. This condition is known as Grave's disease.

In simple words: The thyroid gland makes thyroxine and calcitonin. If thyroxine is too low (hypothyroidism), it can lead to conditions like myxedema (puffy skin, low energy) or goitre (swollen neck) due to lack of iodine. If it's too high (hyperthyroidism), it speeds up the body and can cause exophthalmic goiter (bulging eyes).

🎯 Exam Tip: When describing hormonal disorders, always mention both the hormone involved and whether there is an excess (hyper-) or deficiency (hypo-) to clearly explain the condition.

 

Question 3. Describe briefly the various hormones secreted by Adrenal gland.
Answer: Adrenal cortex:
Structure:

• It is the outer & light yellow colored part which originates from the mesoderm.
• Its weight is about 4 gm & it forms 80 to 85% of the total gland.
• It secretes about many hormones which are collectively called as corticosteroids. They are under the control of ACTH.
• They are also called as life-saving hormones.

The adrenal cortex has 3 parts:
1. Zona glomerulus:

• It is the outer part of the cortex which consists of small & cuboidal cells.
• It secretes mineralocorticoids eg. Aldosterone. These hormones are called as salt retaining hormones.
• These hormones maintain a definite quantity of water, \( Na^{+} \), \( K^{+} \) & \( Cl^{+} \) in the ECF. These hormones stimulate the absorption of \( Na^{+1} \) & \( Cl^{-} \) & excretion of \( K^{+} \) in the kidneys. This precisely regulates electrolyte balance.

2. Zona fasciculate:

• It is the middle part of the cortex which consists of large & polyhedral cells.
• This part secretes glucocorticoids eg. cortisol, corticosterone etc.
• These hormones are used to treat allergy & help in organ transplantation.
• These hormones act as anti-inflammatory & help in the treatment of arthritis.
• These hormones stimulate glycogenesis & gluconeogenesis.

3. Zona reticularis:

• It is the inner zone of the cortex which has cords of polyhedral cells. It also has modified glandular cells.
• Addison's disease: It is caused due to deficiency of mineralocorticoids. Symptoms: Reduced hunger, vomiting, reduced BMR & body temperature, dehydration & bronzing of the skin.
• Conn's disease: It is caused due to excess secretion of mineralocorticoids. Symptoms: Muscle weakness, high BP, malfunctioning of kidneys etc.
• Cushing's disease: It is caused due to hypersecretion of corticosteroids. It is caused due to hypersecretion of corticosteroids which is due to excess of ACTH. Symptoms: Virilism, oedema, hyperglycaemia etc. In virilism, opposite secondary sexual characters appear and it is more common in women. The virilism in a female is also called as hirsutism.

Medulla:

• It is the core part of the adrenal gland which is light brown in color.
• It originates from neural ectoderm.
• This part is not controlled by any pituitary hormone.
• Its chromaffin cells secrete two hormones viz.,
  1. Adrenalin or Epinephrin
  2. Nor-adrenalin or Nor-epinephrin.

These hormones are collectively called as Catecholamines (Amine acid derivatives). These hormones are secreted in the 4:1 ratio. They act as neurotransmitters.
In simple words: The adrenal gland has two main parts: the cortex (outer part) and the medulla (inner part). The cortex makes hormones like aldosterone (for salt balance), cortisol (for stress and sugar), and some sex hormones. The medulla makes adrenaline and nor-adrenaline, which help your body react in emergencies.

🎯 Exam Tip: Clearly differentiate between the adrenal cortex and medulla and the distinct types of hormones each produces, as they have different origins and functions.

 

Question 4. Which hormones are secreted by ovaries? Describe any two of them.
Answer: Ovaries:

• They are female gonads but also act as an endocrine gland. They secrete three types of hormones.
• Its follicular cells & corpus luteum perform an endocrine function.
• In women, the ovaries become active at the age of 12 years. This is known as the beginning of puberty.
• The follicular cells, under the control of FSH, secrete estrogen hormone, also called estradiol or feminizing hormone.
• It is a steroid hormone and performs the following functions:
  It controls oogenesis (egg development).
  It provides secondary sexual characters (like breast development).
  It controls menstrual and oestrous cycles.
  It stimulates the development of mammary glands.
  It controls female sexual accessory organs.
  It controls sexual behavior.
• The corpus luteum of the ovaries secretes progesterone under the control of LH. Progesterone is a steroid hormone also called a pregnancy hormone. It performs the following functions:
  It prepares the uterus for embryonic development. The uterine wall becomes more muscular, glandular & vascular.
  It helps in implantation of the embryo.
  It inhibits oxytocin & ovulation during pregnancy.
  In women, the corpus luteum also secretes relaxin hormone at the time of completion of embryonic development. This hormone helps in parturition by relaxing pubic symphysis.

In simple words: The ovaries make female hormones like estrogen and progesterone. Estrogen helps with female development and the menstrual cycle. Progesterone helps prepare the womb for pregnancy and keeps it healthy during that time.

🎯 Exam Tip: When asked to describe hormones, specify their origin, type (e.g., steroid), and at least two distinct functions for full marks.

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