NCERT Exemplar for Class 11 Biology Chapter-22 (Book Solutions)

Multiple Choice Questions (MCQs)

1. Select the right match for the endocrine gland and its hormones among the options given below.

Options:

(a) A – (IV), B – (ii), C – (iii), D – (I)  

(b) A – (ii), B – (IV), C – (i), D – (iii)

(c) A – (IV), B – (ii), C – (i), D – (iii)

(d) A – (ii), B – (IV), C – (iii), D – (I)

Ans: (d )A – (ii), B – (IV), C – (iii), D – (I)

2. Which of the following hormones is not secreted by the anterior pituitary gland?

(a) Growth hormone

(b) Follicle-stimulating hormone

(c) Oxytocin

(d) Adrenocorticotropic hormone

Ans: (c) Oxytocin 

Explanation: Oxytocin is produced by the posterior pituitary gland.

3. Mary is about to face an interview. But during the first five minutes before the interview, she experiences sweating, increased rate of heartbeat, respiration, etc. Which hormone is responsible for her restlessness?

(a) Estrogen and progesterone

(b) Oxytocin and vasopressin

(c) Adrenaline and noradrenaline 

(d) Insulin and glucagon

Ans: (c) Adrenaline and noradrenaline 

Explanation: These are also called stress hormones. Their primary role is to maintain the body's homeostasis in order to prepare for stressful or harmful situations. The response they produce is known as the fight-or-flight response.

4. The steroid hormone responsible for the balance of water and electrolytes in our body is

(a) Insulin

(b) Melatonin

(c)Testosterone 

(d) Aldosterone

Ans: (d) Aldosterone

Explanation: Aldosterone stimulates reabsorption of ${Na}^{+}$ and water and excretion of ${K}^{+}$ and phosphate ions. Thus, it maintains the balance of water and electrolytes.

5. Thymosin is responsible for

(a) Raising the blood sugar level

(b) Raising the blood calcium level

(c) Differentiation of T lymphocytes 

(d) Decrease in RBC

Ans: (c) Differentiation of T lymphocytes
Explanation: Thymosin is responsible for the differentiation of T lymphocytes

6. In the mechanism of action of a protein hormone, one of the second messengers is

(a) Cyclic AMP

(b) Insulin

(c) ${T_3}$

(d) Gastrin 

Ans:(a)Cyclic AMP

Explanation: Hormones that interact with membrane-bound receptors normally do not enter the target cell, but generate second messengers (Cyclic AMP, $IP_3$, ${Ca}^{2+}$, etc.)

7. Leydig cells produce a group of hormones called

(a) Androgens

(b) Estrogens

(c) Aldosterone

(d) Gonadotropins 

Ans: (a) Androgens

Explanation: Leydig cells produce a group of hormones called androgens.

8. Corpus luteum secretes a hormone called

(a) Prolactin

(b) Progesterone

(c) Aldosterone

(d) Testosterone

Ans: (b) Progesterone

Explanation: Corpus luteum secretes a hormone called Progesterone

9. Cortisol is secreted from

(a) Pancreas

(b) Thyroid 

(c) Adrenal 

(d) Thymus

Ans: (c) Adrenal

Explanation: Cortisol is described as "the stress hormone" by many people. As a "fight or flight" response to stress, the adrenal glands secrete the hormone, which is then released into the bloodstream.

10. A hormone responsible for the normal sleep-wake cycle is

(a) Epinephrine

(b) Gastrin

(c) Melatonin 

(d) Insulin 

Ans: (c) Melatonin

Explanation: A hormone responsible for the normal sleep-wake cycle is Melatonin

11. Hormones are called chemical signals that stimulate specific target tissues. Which is the correct location of these receptors in the case of protein hormones?

(a) Extracellular matrix

(b) Blood

(c) Plasma membrane

(d) Nucleus

Ans: (c) Plasma membrane

Explanation:  Plasma membrane consists of receptors that include protein hormones.

12. Choose the correct option among the following

Options:

(a) A – (ii), B – (I), C – (iii), D – (IV)

(b) A – (IV), B – (I), C – (iii), D – (ii)

(c) A – (I), B – (ii), C – (iii), D – (IV)

(d) A – (i), B – (IV), C – (ii), D – (iii)

Ans: (b) A – (IV), B – (I), C – (iii), D – (ii)

13. Which of the following do not play any role in calcium balance in the human body?

(a) Vitamin D

(b) Parathyroid hormone 

(c) Thyrocalcitonin 

(d) Thymosin

Ans:(d) Thymosin

Explanation: T-lymphocyte differentiation is controlled by the protein thymosin.

14. Which of the following organs in mammals does not consist of a central ‘medullary’ region surrounded by a cortical region?

(a) Ovary

(b) Adrenal 

(c) Liver

(d) Kidney

Ans: (c) Liver

15. Which of the following conditions is not linked to the deficiency of thyroid hormone?

(a) Cretinism 

(b) Goitre

(c) Myxedema

(d) Exophthalmosis

Ans: (d) Exophthalmosis

Explanation: Exophthalmosis happens due to hyperthyroidism.

Very Short Answer Type Questions

1. There are many endocrine glands in the human body. Name the gland which is absent in males and the one which is absent in females.

Ans: Ovary is absent in males and testis is absent in females.

2. Which of the two adrenocortical layers, zona glomerulosa, and zona reticularis lies outside enveloping the other?

Ans: Zone glomerulus is the outermost layer and zone reticular is the innermost layer of the adrenal gland.

3. What is erythropoiesis? Which hormone stimulates it?

Ans: The formation of RBCs from the bone marrow is called erythropoiesis. It is stimulated by the hormone erythropoietin.

4. Name the only hormone secreted by pars intermediate of the pituitary gland.

Ans: Melanocyte Stimulating Hormone (MSH)

5. Name the endocrine gland that produces calcitonin and mention the role played by this hormone.

Ans: Calcitonin or procalcitonin is secreted by the thyroid gland. Calcitonin regulates blood calcium levels.

6. Name the hormone that helps in cell-mediated immunity.

Ans: Thymosin is the hormone that helps in cell-mediated immunity.

7. What is the role of the second messenger in the mechanism of protein hormone action?

Ans: The metabolism of cells is regulated by the second messenger. Hormones that interact with membrane receptors do not ordinarily penetrate the cell. Instead, they produce second messengers, which impact the target cells' function.

8. State whether true or false:

(a) Gastrointestinal tract, kidney, and heart also produce hormones. 

Ans: The given statement is true.

(b) Pars distal produces six trophic hormones.

Ans: The given statement is true.

(c) B-lymphocytes provide cell-mediated immunity.

Ans: The given statement is false. 

(d) Insulin resistance results in a disease called diabetes mellitus. 

Ans: The given statement is true.

9. A patient complains of constant thirst, excessive passing of urine, and low blood pressure. When the doctor checked the patients' blood glucose and blood insulin level, the levels were found to be normal or slightly low. The doctor diagnosed the condition as diabetes insipidus. But he decided to measure one more hormone in the patient's blood. Which hormone does the doctor intend to measure?

Ans: Vasopressin, also known as the Antidiuretic Hormone, because a low quantity of this hormone can cause excessive urine production and low blood pressure.

10. Correct the following statements by replacing the term in the bracket.

(a) Insulin is a (steroid) hormone. 

Ans: (a) Insulin is a peptide hormone.

(b) TSH is secreted from the (corpus) luteum. 

Ans: (b) TSH is secreted from the anterior pituitary gland.

(c) Tetraiodothyronine is an (emergency) hormone.

Ans: (c) Tetraiodothyronine is a maintenance hormone.

(d) The (pineal gland) is located on the anterior part of the kidney.

Ans: (d) The adrenal gland is located on the anterior part of the kidney.

11. Rearrange the following hormones in Column I so as to match with their chemical nature in Column II.

Ans: (a) (iii), (b) (I), (c) (ii), (d) (IV)

Short Answer Type Questions

1. What is the role played by luteinizing hormone in males and females respectively?

Ans: Luteinizing hormones play the following roles: In Males: It stimulates Leydig cell production of testosterone. In Females: It stimulates ovulation.

2. What is the role of the second messenger in hormone action?

Ans: First messengers are extracellular molecules that do not pass the plasma membrane, such as certain hormones. Second messengers are released to enter the cell in such instances. Second messengers cause a cell to undergo a variety of physiological changes. Second messengers are responsible for relaying signals from first messengers.

3. On an educational trip to Uttaranchal, Ketki and her friends observed that many local people were having swollen necks. Please help Ketki and her friends to find out the solutions to the following questions.

(a) Which probable disease are these people suffering from?

Ans: (a) These people are suffering from goiter.

(b) How is it caused?

Ans:(b) Goiter is a disease which is due to deficiency of iodine in the human body.

(c) What effect does this condition have on pregnancy? 

Ans:(C) If a woman is suffering from goiter (which is associated with hypothyroidism); it can have deleterious effects on the fetus. Due to this, the growth of the baby has stopped.

4. George comes on a vacation to India from the US. The long journey disturbs his biological system and he suffers from jet lag. What is the cause of his discomfort?

Ans: The biological clock of 24 hours is a predetermined schedule that is followed by the body. The term for this pattern is circadian rhythm. A person's circadian rhythm gets interrupted when he travels through many time zones over a long period of time. As a result, the person may have jet lag. This could be indicated by sleep abnormalities, bowel habits, anorexia, and other symptoms.

5. Inflammatory responses can be controlled by a certain steroid. Name the steroid, the source from which it is obtained, and also mention its other important functions.

Ans: Cortisol is a steroid that controls inflammatory responses. This hormone is produced by the adrenal cortex. Cortisol is one of the corticoids produced by the adrenal gland. Cortisol influences or modulates many of the physiological changes that occur in response to stress, as well as increasing RBC creation.

6. Old people have weak immune systems. What could be the reason?

Ans: Thymosin, a hormone secreted by the thymus gland, is important for T-lymphocyte development. Cell-mediated immune responses are mediated by T-lymphocytes. The thymus gland degenerates with age, resulting in decreased thymosin output. As a result, elderly adults have a weakened immune system.

7. What are the effects of hypothyroidism (observed during pregnancy) on the development and maturation of a growing baby?

Ans: Hypothyroidism in a pregnant woman can have a negative impact on the growth and maturation of the fetus. The fetus’s growth can be stunted (cretinism), resulting in an underweight infant. Hypothyroidism has long-term consequences, even after birth. The brain of the kid may not develop normally, resulting in mental retardation. A child's skin may be abnormal, and he or she may be deaf.

8. Mention the difference between hypothyroidism and hyperthyroidism

Ans: The difference between hypothyroidism and hyperthyroidism are-

9. You have learned that a characteristic feature of the endocrine system is the presence of feedback loops. By this what is meant is that if hormone A stimulates gland ‘X’ to secrete hormone B, the production of ‘A’ could be modified when the level of B changes in our blood. An example is a relationship between hormones LH and estrogen ($E_2$). An old woman exhibits the following features. High levels of LH in blood but low levels of $E_2$ in the blood. Another woman exhibits a high level of LH in blood and also a high level of $E_2$ in the blood. Where lies the defect in both these women? Provide suitable diagrams to support the answer.

Ans: Before puberty, the level of LH in the blood is normally low, but it rises during the reproductive phase. The amount of LH in the blood during the reproductive phase is determined by the ovulation cycle's phase. When ovulation is approaching, the LH level rises, as does the $E_2$ level. This demonstrates a very regular situation. However, in older women, LH levels are higher, but $E_2$ levels are lower. The presence of a low level of $E_2$ indicates the end of the reproductive period. Menopause is the end of the reproductive cycle, as we all know. There are no or few oocytes remaining in the ovary after menopause. As a result, LH is not being used as effectively as it was during the reproductive period. This explains why elderly women have a higher level of LH in their blood.

Long Answer Type Questions

1. A milkman is very upset one morning as his cow refuses to give any milk. The milkman's wife gets the calf from the shed. On fondling by the calf, the cow gave sufficient milk. Describe the role of the endocrine gland and the pathway associated with this response?

Ans: Milk secretion in mammals is stimulated by the hormone oxytocin which works on a positive feedback mechanism. 

(a) When the calf sucks the cow's udder; it triggers nerve impulses. 

(b) Nerve impulses send signals to the hypothalamus which starts secreting oxytocin.

(c) Oxytocin causes the contraction of smooth muscles around the alveoli (in udder) and milk is released. The following figure shows the positive feedback mechanism of oxytocin.

2. A sample of urine was diagnosed to contain high content of glucose and ketone bodies. Based on this observation, answer the following:

(a) Which endocrine gland and hormone are related to this condition?

Ans:(a) the pancreas is an endocrine gland that produces insulin, which is linked to this illness.

(b) Name the cells on which this hormone acts?

Ans:(b) Insulin affects hepatocytes (liver cells) and adipocytes (fat cells) (cells of fat tissue)

(c) What is the condition called and how can it be rectified?

Ans:(c) Diabetes is the medical term for this illness. Changes in eating habits, medications, and other factors can help. The patient may need to take insulin on a daily basis in some circumstances.

3. Calcium plays a very important role in the formation of bones. Elaborate the role of endocrine glands and hormones responsible for maintaining Calcium homeostasis.

Ans: Calcium homeostasis is the movement of calcium ions between bodily fluids and cells. Calcium plays an important role in various metabolic processes and is also an integral part of the bones. Hence, relative levels of calcium in body fluids, cells, and bones are highly important. Both thyroid and parathyroid hormones have an important role in calcium homeostasis. 

The Role of Thyrocalcitonin (TCT): This hormone is secreted by the thyroid gland. It reduces the blood ${Ca}^{2+}$ Level. Thus, it helps in increasing the availability of calcium to the bones. The function of Parathyroid Hormone: This function is controlled by hormones secreted from the parathyroid gland. It increases the blood ${Ca}^{2+}$ level. Through which the availability of calcium is considered for metabolic functions. It can be said that the roles of TCT and PTH are antagonistic to each other which creates the balance of the effects of each other.

4. Illustrate the differences between the mechanism of action of a protein and a steroid hormone.

Ans:

5. Hypothalamus is a super master endocrine gland. Elaborate.

Ans: The hypothalamus contains nuclei, which are groupings of neuron secretory cells that create hormones. These hormones control the generation and secretion of pituitary hormones. It produces two types of hormones: releasing hormones (which promote pituitary hormone release) and inhibitory hormones (which inhibit pituitary hormone secretion) (that inhibit secretion of pituitary hormones) the pituitary gland secretes the most hormones of all the glands. However, the pituitary gland secretes a number of hormones that regulate the function of other endocrine glands. In reality, the hormones secreted by the pituitary gland influence all of the other endocrine glands. Here are a few examples: Thyroid Stimulating Hormone (TSH) is a hormone that regulates the activity of the thyroid gland.