Important Questions Class 11 Biology Chapter 19 Chemical Coordination and Integration

Important Questions Class 11 Biology Chapter 19 Chemical Coordination and Integration

Chemical Coordination and Integration is Chapter 19 of Class 11 Biology. Hormones are chemical messengers made by endocrine glands (glands without ducts) and carried by the blood to the organs where they act. The chapter explains the human endocrine system, including the hypothalamus, pituitary, thyroid, parathyroid, adrenal, pancreas, testis and ovary, the hormones they secrete and how hormones act on their target cells.

This page gives 12 important questions from Chemical Coordination and Integration with clear answers prepared by Extramarks experts. The questions cover insulin and glucagon, hormones of the pituitary gland, the mechanism of action of FSH (follicle stimulating hormone) and steroid hormones, hormone deficiency disorders and the location of the endocrine glands. Students can use them for school tests and CBSE (Central Board of Secondary Education) exam revision, and teachers and parents can use them for quick practice.

Q1. What is insulin and what are its functions?

Answer: Insulin is a peptide hormone secreted by β-cells of the pancreas.

Functions of Insulin:

• It is a hypoglycemic hormone, i.e. it reduces the level of glucose in the blood by stimulating the uptake and utilisation of glucose by tissue cells.
• It acts on the hepatocytes and stimulates the conversion of glucose to glycogen (glycogenesis). Deficiency of insulin causes hyperglycemia and prolonged hyperglycemia leads to a complex disorder called diabetes mellitus.

Q2. Give the name of hormones secreted by pars distalis and pars intermedia.

Answer: Pars distalis region produces growth hormone (GH), prolactin (PRL), thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), luteinizing hormone (LH) and follicle stimulating hormone (FSH). Pars intermedia secretes only one hormone called melanocyte-stimulating hormone (MSH).

Q3. Match the following:

Answer:

Q4. Briefly mention the mechanism of action of FSH.

Answer: Follicle Stimulating Hormone (FSH) is synthesised and secreted by the anterior lobe of the pituitary gland. FSH, being a glycoprotein, is insoluble in lipid thus, cannot enter the target cells. So, these glycoproteins first bind with the specific receptor molecules, that are found on the surface of a cell membrane, form a hormone-receptor complex and activate the cellular system to perform functions.

Mechanism of Action: After the release of FSH from the site of production, it reaches the ovary, uterus or testis and binds to FSH receptor, present at the plasma membrane of these organs. FSH receptor is a transmembrane G-protein coupled receptor protein. The binding of FSH to receptor generates second messengers (cAMP). Secondary messengers start several biochemical changes inside these organs and carry out many important functions.

Functions:

• In the ovary, it results in follicular development.
• In the uterus, it is involved in the development of secretory endometrium during the luteal phase.
• In the males, the FSH is responsible for spermatogenesis.

Q5. Which hormonal deficiency is responsible for the following?
(a) Diabetes mellitus
(b) Goitre
(c) Cretinism

Answer: (a) Diabetes mellitus: Diabetes mellitus is caused by deficiency of insulin. It is also caused when insulin becomes non-responsive to blood glucose level.

(b) Goitre: Goitre is the enlargement of thyroid glands and happens due to the deficiency of thyroid hormones.

(c) Cretinism: It is caused by low level of thyroid hormones during pregnancy that results in the stunted growth of baby.

Q6. 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

Answer: (a) Hyperglycemic hormone and hypoglycemic hormone: Hyperglycemic hormone- Glucagon, Hypoglycemic hormone- Insulin

(b) Hypercalcemic hormone: Parathyroid hormone

(c) Gonadotrophic hormones: Luteinising hormone, follicle-stimulating hormone

(d) Progestational hormone: Progesterone

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

(f) Androgens and estrogens: Androgen- Testosterone, Estrogen- Estradiol

Q7. 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

Answer: (a) Parathyroid hormone (PTH): Parathyroid hormone is a peptide hormone and secreted by parathyroid glands. It plays a significant role in:

Calcium homeostasis in the body. It increases the calcium level in blood. It also stimulates calcium absorption from digested food and reabsorption of Ca⁺⁺ by renal tubules.

It stimulates the dissolution and demineralisation of bones.

(b) Thyroid hormones: Thyroxine (T₄), tri-iodothyronine (T₃) and thyrocalcitonin are collectively called as thyroid hormones. Iodine is essential for an adequate rate of thyroid hormone synthesis. Low level of thyroid hormones (hypothyroidism) results in enlargement of the thyroid gland, commonly called goitre. Excessive synthesis of thyroid hormones is called hyperthyroidism which is also harmful to the body. Thyroid hormones are essential for many physiological processes.

They play an important role in maintaining normal basal metabolic rate (BMR).

They control the metabolism of carbohydrates, proteins and fats.

They also help in red blood cell (RBCs) formation and regulating blood calcium levels.

They also influence water and electrolytes balance.

(c) Thymosins: It is a peptide hormone and secreted by the thymus. Its functions are:

• Differentiation of T-lymphocytes which are essential for cell-mediated immunity.
• Promotes antibody production which provides humoral immunity.

(d) Androgens: Androgens are a group of hormones. Main androgen hormone is testosterone hormone. Androgens are secreted by leydig cells of testes. The main functions of androgens are:

• It stimulates the development of male secondary sex characteristics.
• It is required for the development, maturation and functions of the male accessory sex organs like epididymis, vas deferens, seminal vesicles, prostate gland, urethra, etc.
• It stimulates spermatogenesis (formation of spermatozoa) and influence male sexual behaviour (libido).

(e) Estrogens: Estrogen is a steroid hormone produced by the ovaries. The main functions of estrogen are:

• It stimulates the development of female secondary sex organs.
• It helps in the development of ovarian follicles and mammary glands.
• It also regulates female sexual behaviour.

(f) Insulin and Glucagon: Functions of Insulin and glucagon:

Insulin stimulates uptake of excess glucose and its utilisation by liver cells by the process of glycogenesis. In glycogenesis, excess glucose is converted into its polymer glycogen and stored in the liver cells. Deficiency of insulin results in a disease, called diabetes mellitus. Glucagon acts in just the opposite manner. In case of low glucose level in blood, it stimulates the breakdown of glycogen and release of glucose in the bloodstream. It also stimulates the synthesis of glucose from non-carbohydrate substrates like pyruvate, lactate, glycerol, etc., by the process of gluconeogenesis.

Q8. List the hormones secreted by the following:
(a) Hypothalamus
(b) Pituitary
(c) Thyroid
(d) Parathyroid
(e) Adrenal
(f) Pancreas
(g) Testis
(h) Ovary
(i) Thymus
(j) Atrium
(k) Kidney
(l) G-I Tract

Answer: (a) Hypothalamus: Two types of hormones are secreted by hypothalamus:

(i) Releasing hormones: Gonadotropin releasing hormone, thyrotrophin releasing hormone, somatotrophin releasing hormone and adrenocorticotrophin releasing hormone

(ii) Inhibiting hormones: Somatostatin, growth-inhibiting hormone and melanocyte-inhibiting hormone

(b) Pituitary: List of hormones secreted by two different parts of the pituitary gland:

(i) Hormones secreted by Adenohypophysis: Growth hormone (GH), prolactin, thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), luteinizing hormone (LH), melanocyte stimulating hormone (MSH) and follicle stimulating hormone (FSH)

(ii) Hormones secreted by Neurohypophysis: Oxytocin and vasopressin

(c) Thyroid: Thyroxin (T₄), triiodothyronine (T₃) and thyrocalcitonin

(d) Parathyroid: Parathyroid hormone (PTH)

(e) Adrenal: List of hormones secreted by adrenal gland:

• Corticoid hormones are secreted by adrenal cortex. Corticoids are further divided into
• -glucocorticoid (hormone secreted is cortisol)
• -mineralocorticoid (hormone secreted is aldosterone).
• Catecholamines are secreted by adrenal medulla. It secretes adrenaline (also called epinephrine) and noradrenaline (also called norepinephrine).

(f) Pancreas: Insulin and glucagon

(g) Testis: Testosterone

(h) Ovary: Estrogen and progesterone

(i) Thymus: Thymosins

(j) Atrium: Atrial natriuretic hormone (ANH)

(k) Kidney: Erythropoietin

(l) G-I Tract: Gastrin, secretin, cholecystokinin and gastric inhibitory peptide (GIP, also known as glucose-dependent insulinotropic peptide).

Q9. Diagrammatically indicate the location of the various endocrine glands in our body.

Answer: Diagrammatic representation of the location of various endocrine glands in our body:

Q10. Define the following:
(a) Exocrine gland
(b) Endocrine gland
(c) Hormone

Answer: (a) Exocrine gland: The glands which secrete their products via a duct are called exocrine glands. Examples: sweat glands, salivary glands, mammary glands and liver.

(b) Endocrine gland: The glands that do not secrete their products (hormones) via any duct, but directly secrete them into the bloodstream or into its surrounding tissues are known as endocrine glands. Examples: adrenal gland, pituitary gland and thyroid glands.

(c) Hormone: The secretions of endocrine glands that perform their function at a distant location, away from the location of their origin by travelling through the bloodstream are called hormones. They can also diffuse to their neighbouring tissues.

Current scientific definition defines hormones as “Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts.” Example: thyroid hormone, follicle stimulating hormone, testosterone.

Q11. What is CCK-PZ? What are its functions?

Answer: CCK-PZ is cholecystokinin pancreozymin. It is a hormone secreted from the duodenal walls in response to fatty food in the duodenum. It stimulates contraction of gall bladder for release of bile and secretion of enzymes from pancreas.

Q12. How does a steroid hormone act on its target cell?

Answer:

• Steroids are lipid soluble hormones which can easily cross the cell membrane and hence bind with cytosolic receptor.
• The hormone-receptor complex enters the nucleus and binds to specific regulatory sites on the chromosomes.
• The binding alters the pattern of gene expression, initiating the transcription of some genes (DNA), while repressing the transcription of others.
• This results in the production of specific mRNA translation products, proteins and usually enzymes.
• The actions of lipid soluble hormones are slower and last longer than the actions of water soluble hormones.

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