NCERT Solutions for Class 11 Biology Chapter 22: Chemical Coordination and Integration

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1. Define the following:

(a) Exocrine gland

(b) Endocrine gland

(c) Hormone

Ans. (a) Exocrine gland: Exocrine gland is a gland that secretes on the surface or into a particular region of the body through a duct. Example: sebaceous glands, salivary glands and sweat glands etc.

(b) Endocrine gland: The gland that does not secret into the duct but directly discharges in the bloodstream and then conveys it to the target organ is called the endocrine gland. Example: Pituitary gland, thyroid gland, adrenal gland, etc.

(c) Hormone: Hormones are non-nutrient chemicals which are produced in trace amounts and delivered through the bloodstream at the required locations to act
as an intercellular messenger and influence in synthesising, activation and inhibition of metabolic processes in the body.

2. Diagrammatically indicate the location of the various endocrine glands in our body.

Ans. The location of the various endocrine glands in our body is shown below:

Chemical Coordination andans2

3. List the hormones secreted by the following:
(a) Hypothalamus (e) Adrenal (i) Thymus
(b) Pituitary (f) Pancreas (j) Atrium
(c) Thyroid (g) Testis (k) Kidney
(d) Parathyroid (h) Ovary (l) G-I Tract

Ans. (a) Hypothalamus: There are two types of hormones produced by the hypothalamus and known as releasing hormones and inhibiting hormones.

Releasing hormones Inhibiting hormones
  1. Thyrotrophin releasing hormone
 Somatostatin hormone
  1. Adrenocorticotrophin releasing hormone
 Growth-inhibiting hormone
  1. Growth hormone releasing hormone
 Melanocyte inhibiting hormone [MSH]
  1. Melanocyte stimulating hormone [MSH]
  1. Gonadotrophins

(b) Pituitary:

Adenohypophysis Neurohypophysis
Pars distalis portion Pars intermedia portion
  1. Growth hormone (GH)
 Melanocyte stimulating hormone [MSH]. Oxytocin
  1. Prolactin (PRL)
 Vasopressin
  1. Thyroid Stimulating Hormone (TSH)
  1. Adrenocorticotrophic Hormone (ACTH)
  1. Luteinizing Hormone (LH)
  1. Follicle-stimulating Hormone (FSH)

(c) Thyroid:

Hormones
  1. Calcitonin.
  1. Tri-iodothyronine (T3)
  1. Tetra-iodothyronine / Thyroxine (T4)

(d) Parathyroid:

Hormones
  1. Parathormone

(e) Adrenal: Hormones of the adrenal cortex are grouped into three categories:

Adrenal cortex Adrenal medulla
Glucocorticoids Mineralocorticoids Sexcorticoids
Cortisol Aldosterone Testosterone Adrenaline
Tri-iodothyronine (T3) Nor-adrenaline
Tetra-iodothyronine / Thyroxine (T4)

(f) Pancreas:

Hormones
  1. Insulin
  1. Glucagon
  1. Somatostatin

(g) Testis:

Hormones
  1. Testosterone
  1. Androsterone

(h) Ovary:

Hormones
  1. Relaxin
  1. Oestrogen
  1. Progesterone

(i) Thymus:

Hormones
  1. Thymosin

(j) Atrium:

Hormones
  1. Atrial natriuretic factor

(k) Kidney:

Hormones
  1. Erythropoietin

(1) G-I tract:

4. Fill in the blanks:

Intestine Stomach Liver
  1. Secretin
 Gastrin Angiotensinogen
  1. Enterogastrone
  1. Enterocrinin
  1. Duocrinin
  1. Cholecystokinin
Hormones Target gland
(a) Hypothalamic hormones __________
(b) Thyrotrophin (TSH) __________
(c) Corticotrophin (ACTH) __________
(d) Gonadotrophins (LH, FSH) __________
(e) Melanotrophin (MSH) __________

Ans. 

Hormones → Target gland
(a) Hypothalamic hormones → Pituitary gland.
(b) Thyrotrophin (TSH) → Thyroid gland.
(c) Corticotrophin (ACTH) → Adrenal cortex.
(d) Gonadotrophins (LH, FSH) → Testis and Ovaries.
(e) Melanotrophin (MSH) → Pigment (melanocyte) cells of the skin.

5. Write short notes on the functions of the following hormones:

(a) Parathyroid hormone (PTH)

(b) Thyroid hormones

(c) Thymosins

(d) Androgens

(e) Estrogens

(f) Insulin and Glucagon

Ans. (a) Parathyroid hormone (PTH): Parathyroid hormone maintains the calcium level in the body and stimulates bone absorption which demineralises bones increasing blood calcium levels. It also helps to increase calcium absorption by renal tubules and from the digested food.

(b) Thyroid hormone: These are two types namely Thyroxine (T4) and Tri-iodothyronine (T3). Former hormone i.e., T4 regulates the basal metabolic rate and controls body weight, body growth and metamorphosis of the tadpole larva into an adult frog. This also suppresses RBC formation. The T3 hormone increases oxygen content in body cells and energy consumption. It also increases the heart rate and force of contraction which increases the cardiac output.

(c) Thymosins: Thymosin stimulates the differentiation of T-lymphocytes and provides cell-mediated immunity. It also promotes the production of antibodies to provide humoral immunity.

(d) Androgens: These are of two types: Testo-sterone and Androsterone. Testosterone helps in the maturation of sperms and stimulates the growth of the reproductive system. It also helps in the development of secondary sexual characters of men. It produces anabolic effects on protein and carbohydrate metabolism. Androsterone affects the masculinisation of the foetus and child and also maintains or creates masculine traits in adults.

(e) Estrogens: The primary function of estrogens is the development of female secondary sexual characteristics. These include breasts, endometrium, regulation of the menstrual cycle, etc. In males, estrogen helps in the maturation of the sperm and the maintenance of a healthy libido.

(f) Insulin and glucagon: Insulin plays a major role in the regulation of glucose homeostasis. It regulates the transport of glucose from the blood to the muscles. It promotes the oxidation of glucose and conversion to glycogen by the glycogenesis process. On the other hand, glucagon maintains the normal glucose level in the blood. It acts on hepatocytes and stimulates the conversion of glycogen to glucose by the glycogenolysis process. It also stimulates the Gluconeogenesis process for the conversion of non-carbohydrates to glucose.

6. Give example(s) of:

(a) Hyperglycemic hormone and hypoglycemic hormone

(b) Hypercalcemic hormone

(c) Gonadotrophic hormones

(d) Progestational hormone

(e) Blood pressure lowering hormone

(f) Androgens and estrogens

Ans. (a) Hyperglycemic hormone and hypoglycemic hormone: Glucagon and Insulin.

(b) Hypercalcemic hormone: Parathormone.

(c) Gonadotrophic
hormones: Follicle-stimulating hormone and Luteinizing hormone.

(d) Progestational hormone: Progesterone.

(e) Blood pressure lowering hormone: Atrial natriuretic factor.

(f) Androgens and estrogens: Testosterone and Estradiol.

7. Which hormonal deficiency is responsible for the following:

(a) Diabetes mellitus

(b) Goitre

(c) Cretinism

Ans. (a) Diabetes mellitus: Responsible hormone is insulin.

(b) Goitre: Responsible hormone is thyroxine.

(c) Cretinism: Responsible hormone is thyroxine.

8. Briefly mention the mechanism of action of FSH.

Ans. Follicle-stimulating hormone is a glycoprotein and hence it is insoluble in lipids. Therefore it cannot enter the target cells. It binds to the specific receptor molecules located on the surface of the cell membrane to form a hormone-receptor complex. This complex causes the release of an enzyme adenylate cyclase from the receptor site. This enzyme forms the cyclic adenosine monophosphate (cAMP) from ATP. This cAMP activates the existing enzyme system of the cell which results in accelerated metabolic reactions in the cell. The hormone is called the first messenger and the cAMP is termed as the second messenger. The hormone-receptor complex changes the permeability of the cell membrane to facilitate the passage of materials through it. This increases the activities of the cell as it receives the desired materials.

9. Match the following:

Column I Column II
(a) T4 (i) Hypothalamus
(b) PTH (ii) Thyroid
(c) GnRH (iii) Pituitary
(d) LH (iv) Parathyroid

Ans. The correct match is as follows:

Column I Column II
(a) T4 (ii) Thyroid
(b) PTH (iv) Parathyroid
(c) GnRH (i) Hypothalamus
(d) LH (iii) Pituitary

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