NCERT Solutions for Class 11 Biology Chapter 19: Chemical Coordination and Integration

(a) Exocrine gland: Exocrine glands are glands that have ducts to carry their secretions to a specific location. Their secretions are released onto the body surface or into body cavities.

• Examples: Salivary glands (secrete saliva), sweat glands (secrete sweat), and sebaceous glands (secrete oil).

(b) Endocrine gland: Endocrine glands are also known as ductless glands. They release their chemical products, called hormones, directly into the bloodstream. The blood then carries these hormones to target cells or organs throughout the body.

• Examples: Pituitary gland, thyroid gland, and adrenal gland.

(c) Hormone: Hormones are non-nutrient chemical messengers produced by endocrine glands in very small amounts. They are transported via the blood to distant target organs, where they regulate various physiological processes like growth, metabolism, and reproduction.

Students should draw a simple outline of the human body and label the following glands at their correct locations:

1. Pineal Gland: Located on the dorsal side of the forebrain.
2. Hypothalamus: Located at the base of the forebrain.
3. Pituitary Gland: Located in a bony cavity called sella turcica, attached to the hypothalamus.
4. Thyroid Gland: Located in the neck region, on either side of the trachea.
5. Parathyroid Glands: Four small glands located on the back side of the thyroid gland.
6. Thymus Gland: Located on the dorsal side of the heart and the aorta.
7. Pancreas: Located in the abdominal cavity, just behind the stomach. (It's both an exocrine and endocrine gland).
8. Adrenal Glands: Located on the anterior part of each kidney (like a cap).
9. Gonads:
   • Testes (in males): Located in the scrotal sac.
   • Ovary (in females): Located in the lower abdominal cavity.

This is a very important question for exams. Here's a clear list:

(a) Parathyroid hormone (PTH): PTH is a hypercalcemic hormone, meaning it increases blood calcium (Ca²⁺) levels.

• It stimulates bone resorption (dissolution), releasing calcium into the blood.
• It promotes reabsorption of Ca²⁺ by the renal tubules in the kidneys.
• It increases Ca²⁺ absorption from digested food.

(b) Thyroid hormones (T3 & T4): These hormones regulate the basal metabolic rate (BMR).

• They support red blood cell formation.
• They control the metabolism of carbohydrates, proteins, and fats.
• They are essential for normal growth and mental development.

(c) Thymosins: Thymosins play a major role in the development of T-lymphocytes, which provide cell-mediated immunity. They also promote antibody production for humoral immunity. The thymus degenerates with age, weakening the immune response in old individuals.

(d) Androgens (e.g., Testosterone): These are male sex hormones that regulate the development of male accessory sex organs, stimulate male secondary sexual characters (deep voice, beard), and promote spermatogenesis.

(e) Estrogens: These are female sex hormones responsible for the development of female secondary sex organs and characters (high-pitched voice, mammary glands). They also regulate the menstrual cycle.

(f) Insulin and Glucagon: These pancreatic hormones are antagonistic and regulate blood glucose.

• Insulin (Hypoglycemic): It lowers blood glucose by promoting its uptake by cells and conversion to glycogen.
• Glucagon (Hyperglycemic): It raises blood glucose by stimulating the breakdown of glycogen into glucose.

(a) Hyperglycemic hormone: Glucagon; Hypoglycemic hormone: Insulin

(b) Hypercalcemic hormone: Parathyroid hormone (PTH)

(c) Gonadotrophic hormones: Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH)

(d) Progestational hormone: Progesterone

(e) Blood pressure lowering hormone: Atrial Natriuretic Factor (ANF)

(f) Androgens: Testosterone; Estrogens: Estradiol

(a) Diabetes mellitus: Caused by the deficiency of Insulin. This leads to high blood sugar (hyperglycemia).

(b) Goitre: Caused by the deficiency of Iodine in the diet, which is required for thyroid hormone synthesis. The thyroid gland enlarges.

(c) Cretinism: Caused by the deficiency of thyroid hormone (hypothyroidism) during pregnancy. It results in stunted growth and mental retardation in the baby.

FSH is a protein hormone and cannot enter the target cell. It uses a second messenger system:

1. Binding to Receptor: FSH binds to a specific receptor on the outer surface of the target cell membrane (e.g., ovarian cell).
2. Response Generation: This activates an enzyme, adenylate cyclase, inside the cell.
3. Second Messenger Formation: Adenylate cyclase converts ATP into cyclic AMP (cAMP), the second messenger.
4. Cellular Response: cAMP activates a cascade of enzymes, leading to physiological responses like the growth of ovarian follicles.

Diabetes Mellitus: Caused by the deficiency of insulin. It is characterized by hyperglycemia (high blood sugar) and the presence of glucose in the urine (glycosuria).

Diabetes Insipidus: Caused by the deficiency of Anti-Diuretic Hormone (ADH). It is characterized by excessive urination (polyuria) and thirst (polydipsia) without high blood sugar.

The pituitary gland is called the 'Master Gland' because it secretes several hormones (like TSH, ACTH, FSH, LH) that control the functioning of almost all other endocrine glands in the body, such as the thyroid, adrenal glands, and gonads.

Antagonistic hormones are pairs of hormones that have opposite effects on a target tissue to maintain homeostasis. A classic example is Insulin and Glucagon. Insulin lowers blood glucose levels by promoting its uptake by cells, while Glucagon raises blood glucose levels by stimulating its release from liver glycogen.

Mechanism of Steroid Hormone Action:

Steroid hormones (like testosterone, estrogen) are lipid-soluble and can easily pass through the cell membrane.

1. Entry into Cell: The hormone diffuses across the cell membrane into the cytoplasm.
2. Binding to Intracellular Receptor: Inside the cell, it binds to a specific intracellular receptor, forming a hormone-receptor complex.
3. Action on Genome: This complex enters the nucleus and binds to a specific region of the DNA.
4. Gene Expression & Protein Synthesis: This binding initiates transcription of specific genes into mRNA, which is then translated to produce new proteins.
5. Physiological Response: These new proteins carry out the physiological effects of the hormone.

Difference from Protein Hormone Action:

The adrenal glands sit on top of the kidneys. Each gland has two parts: the outer adrenal cortex and the inner adrenal medulla.

1. Adrenal Medulla:

This part secretes catecholamines: Adrenaline (Epinephrine) and Noradrenaline (Norepinephrine). They are known as "fight-or-flight" hormones, released during stress.

• Functions: They increase alertness, heart rate, respiration rate, and blood glucose levels.

2. Adrenal Cortex:

This part secretes hormones called corticoids.

• Glucocorticoids (mainly Cortisol): Known as stress-combat hormones. They are involved in carbohydrate metabolism (gluconeogenesis), have anti-inflammatory properties, and suppress the immune response.
• Mineralocorticoids (mainly Aldosterone): Regulate water and electrolyte balance. Aldosterone promotes reabsorption of Na⁺ and water, maintaining blood pressure.
• Sex Corticoids: Small amounts of androgenic steroids that contribute to the growth of hair during puberty.

Based on these symptoms, here are the answers:

1. Which endocrine gland is likely affected?
   The thyroid gland is likely affected.
2. What condition is she suffering from?
   She is likely suffering from Hypothyroidism (under-activity of the gland).
3. What element is crucial for this gland?
   The crucial chemical element is Iodine.
4. If this occurred in a child, what would it be called?
   In a child, this condition leads to Cretinism.