Chemical Coordination and Integration
NCERT Class 11 Biology • Chapter 19 Solutions
Endocrine System Basics
1. Define (a) Exocrine gland (b) Endocrine gland (c) Hormone.
- (a) Exocrine Gland: Glands that secrete their products (enzymes, saliva, etc.) through ducts to a specific location (e.g., Sweat glands, Salivary glands).
- (b) Endocrine Gland: Ductless glands that secrete their products (hormones) directly into the blood stream to be transported to distant target organs (e.g., Thyroid, Pituitary).
- (c) Hormone: Non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts.
2. Diagrammatically indicate the location of various endocrine glands.
Locations:
- Head: Hypothalamus, Pituitary, Pineal.
- Neck: Thyroid, Parathyroid.
- Thorax: Thymus.
- Abdomen: Pancreas, Adrenal.
- Pelvis: Testis (Male), Ovary (Female).
Hormones Secreted by Glands
3. List the hormones secreted by the following:
| Gland/Organ | Hormones Secreted |
|---|---|
| (a) Hypothalamus | Releasing Hormones (e.g., GnRH), Inhibiting Hormones (e.g., Somatostatin). |
| (b) Pituitary | GH, PRL, TSH, ACTH, LH, FSH, MSH (Adenohypophysis); Oxytocin, Vasopressin (Neurohypophysis). |
| (c) Thyroid | Thyroxine ($T_4$), Triiodothyronine ($T_3$), Thyrocalcitonin (TCT). |
| (d) Parathyroid | Parathyroid Hormone (PTH). |
| (e) Adrenal | Cortex: Cortisol, Aldosterone, Androgens. Medulla: Adrenaline, Noradrenaline. |
| (f) Pancreas | Insulin, Glucagon. |
| (g) Testis | Androgens (Testosterone). |
| (h) Ovary | Estrogen, Progesterone. |
| (i) Thymus | Thymosins. |
| (j) Atrium | Atrial Natriuretic Factor (ANF). |
| (k) Kidney | Erythropoietin. |
| (l) G-I Tract | Gastrin, Secretin, Cholecystokinin (CCK), GIP. |
Target Organs & Functions
4. Fill in the blanks: Hormones -> Target Gland.
- (a) Hypothalamic hormones $\rightarrow$ Pituitary Gland
- (b) Thyrotrophin (TSH) $\rightarrow$ Thyroid Gland
- (c) Corticotrophin (ACTH) $\rightarrow$ Adrenal Cortex
- (d) Gonadotrophins (LH, FSH) $\rightarrow$ Gonads (Testis/Ovary)
- (e) Melanotrophin (MSH) $\rightarrow$ Skin (Melanocytes)
5. Write short notes on the functions of the following hormones.
- (a) PTH: Increases blood $Ca^{2+}$ levels (Hypercalcemic) by bone resorption and reabsorption by renal tubules.
- (b) Thyroid Hormones: Regulate Basal Metabolic Rate (BMR), support RBC formation, control metabolism of carbohydrates, proteins, and fats.
- (c) Thymosins: Differentiate T-lymphocytes (Cell-mediated immunity) and promote antibody production (Humoral immunity).
- (d) Androgens: Regulate development of male accessory sex organs and secondary sexual characters (facial hair, low pitch voice).
- (e) Estrogens: Stimulate growth of female secondary sex organs, appearance of secondary sexual characters (high pitch voice), and mammary gland development.
- (f) Insulin & Glucagon:
- Insulin: Lowers blood glucose (Hypoglycemic) by enhancing cellular uptake.
- Glucagon: Increases blood glucose (Hyperglycemic) by stimulating glycogenolysis.
Examples & Disorders
6. Give examples of hormones.
- (a) Hyperglycemic: Glucagon; Hypoglycemic: Insulin.
- (b) Hypercalcemic: Parathyroid Hormone (PTH).
- (c) Gonadotrophic: LH, FSH.
- (d) Progestational: Progesterone.
- (e) Blood pressure lowering: Atrial Natriuretic Factor (ANF).
- (f) Androgens: Testosterone; Estrogens: Estradiol.
7. Which hormonal deficiency causes the following?
- (a) Diabetes mellitus: Insulin deficiency.
- (b) Goitre: Thyroxine ($T_3/T_4$) deficiency (due to Iodine deficiency).
- (c) Cretinism: Thyroid hormone deficiency (Hypothyroidism) during pregnancy/infancy.
Mechanism of Action
8. Briefly mention the mechanism of action of FSH.
[Image of Protein Hormone Mechanism Diagram]
FSH is a peptide/protein hormone (lipid insoluble). It cannot enter the target cell directly.
- Binding: FSH binds to specific membrane-bound receptors on the ovarian cell surface.
- Second Messenger: This binding generates a second messenger (e.g., Cyclic AMP or $Ca^{++}$).
- Cascade: The second messenger triggers a cascade of biochemical responses inside the cell.
- Result: Physiological changes occur (e.g., ovarian follicle growth).
9. Match the following.
| Column I | Column II |
|---|---|
| (a) $T_4$ | (ii) Thyroid |
| (b) PTH | (iv) Parathyroid |
| (c) GnRH | (i) Hypothalamus |
| (d) LH | (iii) Pituitary |