NCERT Solutions for Class 11 Biology Chapter 19 Chemical Coordination and Integration
NCERT Solutions for Class 11 Biology Chapter 19 Chemical Coordination and Integration provides revision notes and comprehensive textbook solutions covering endocrine glands, hormones, mechanism of hormone action, non-endocrine tissue secretions, and hormonal disorders.
Overview of Topics & Subtopics (Click to Jump)
1. Endocrine Glands & Definition of Hormones
Short Note:
• Endocrine Glands: Ductless glands that secrete chemical messengers directly into the bloodstream to reach distant target organs.
• Definition of Hormones: Hormones are non-nutrient chemicals produced in trace amounts that act as intercellular messengers.
• Endocrine vs Exocrine Glands: Exocrine glands release secretions via ducts to epithelial surfaces (e.g., salivary, sweat, digestive glands), whereas endocrine glands release hormones directly into extracellular fluid/blood without ducts.
2. Human Endocrine System (Major Glands & Functions)
Short Note:
• Hypothalamus: Basal part of diencephalon. Secretes Releasing Hormones (e.g., GnRH) and Inhibiting Hormones (e.g., Somatostatin) to control the pituitary gland.
• Pituitary Gland (Master Gland): Located in sella turcica of sphenoid bone. Divided into:
- Adenohypophysis (Anterior Pituitary): GH (Growth Hormone), PRL (Prolactin), TSH (Thyroid Stimulating Hormone), ACTH (Adrenocorticotropic Hormone), LH (Luteinizing Hormone), and FSH (Follicle Stimulating Hormone).
- Neurohypophysis (Posterior Pituitary): Stores and releases Oxytocin (uterine contractions, milk ejection) and Vasopressin / ADH (water reabsorption in kidneys), which are synthesized by the hypothalamus.
• Pineal Gland: Secretes Melatonin; regulates 24-hour diurnal (circadian) rhythm, sleep-wake cycle, and body temperature.
• Thyroid Gland: Secretes Thyroxine (T₄), Triiodothyronine (T₃) (regulate basal metabolic rate, BMR), and Thyrocalcitonin (TCT) (lowers blood calcium level).
• Parathyroid Gland: Secretes Parathyroid Hormone (PTH); hypercalcemic hormone that increases blood calcium levels by reabsorbing Ca²⁺ from bones and kidney tubules.
• Thymus Gland: Secretes Thymosins; crucial for differentiation of T-lymphocytes (cell-mediated immunity). Degenerates in old age.
• Adrenal Gland:
- Adrenal Cortex: Secretes Glucocorticoids (e.g., Cortisol - gluconeogenesis, anti-inflammatory) and Mineralocorticoids (e.g., Aldosterone - Na⁺ and water reabsorption).
- Adrenal Medulla: Secretes Catecholamines: Adrenaline / Epinephrine and Noradrenaline / Norepinephrine (emergency / 3F hormones: Fight, Flight, Fright).
• Pancreas (Composite Gland): Islets of Langerhans contain α-cells (secrete Glucagon - hyperglycemic) and β-cells (secrete Insulin - hypoglycemic).
• Gonads: Testes (Androgens / Testosterone - male secondary sexual characteristics) and Ovaries (Estrogen and Progesterone - female reproduction & menstrual cycle regulation).
3. Hormones of Non-Endocrine Tissues & Mechanism of Hormone Action
Short Note:
• Hormones from Non-Endocrine Tissues:
- Heart: Atrial walls secrete Atrial Natriuretic Factor (ANF) which decreases blood pressure by dilating blood vessels.
- Kidney: Juxtaglomerular (JG) cells produce Erythropoietin which stimulates erythropoiesis (RBC formation).
- Gastrointestinal (GI) Tract: Secretes Gastrin (HCl secretion), Secretin (water and bicarbonate secretion), CCK / Cholecystokinin (bile & pancreatic enzyme secretion), and GIP (inhibits gastric secretion).
• Mechanism of Hormone Action:
- Water-Soluble Hormones (Protein/Peptide Hormones e.g., Insulin, FSH): Bind to extracellular cell-membrane receptors → generate second messengers (e.g., cyclic AMP, IP₃, Ca²⁺) → trigger biochemical response.
- Lipid-Soluble Hormones (Steroid Hormones e.g., Estrogen, Cortisol, Iodothyronines): Pass through plasma membrane → bind to intracellular receptors inside nucleus → interact with genome to regulate gene expression.
4. Endocrine Disorders & Hormonal Imbalances
Short Note:
• Pituitary Disorders:
- Gigantism / Acromegaly: Hypersecretion of Growth Hormone (GH) in childhood / adulthood.
- Pituitary Dwarfism: Hyposecretion of GH during growth years.
- Diabetes Insipidus: Hyposecretion of ADH leading to excessive water loss via urine and severe thirst.
• Thyroid Disorders:
- Goitre: Enlargement of thyroid gland due to iodine deficiency.
- Cretinism: Hypothyroidism during pregnancy causing stunted physical and mental growth in baby.
- Grave's Disease (Exophthalmic Goitre): Hyperthyroidism characterized by enlarged thyroid, protruding eyes, and increased BMR.
• Adrenal Disorders:
- Addison's Disease: Hyposecretion of adrenal cortex hormones causing weakness, skin pigmentation, and low blood pressure.
• Pancreatic Disorders:
- Diabetes Mellitus: Deficiency or hyposecretion of Insulin leading to prolonged hyperglycemia, glycosuria (glucose in urine), and ketone body formation.
Intext & Conceptual Questions
• Peptide / Protein Hormones: These hormones are water-soluble and cannot cross the lipid bilayer of target cell membranes. They bind to specific extracellular receptors on the cell membrane, generating intracellular second messengers (e.g., cAMP, IP₃, Ca²⁺). These second messengers activate cascade enzyme reactions to regulate cellular metabolism.
• Steroid Hormones: These hormones are lipid-soluble and easily cross the cell membrane. They enter the cell and bind to intracellular receptors (mostly nuclear receptors). The hormone-receptor complex interacts directly with the nuclear DNA to regulate transcription and gene expression.
• Diabetes Mellitus: Caused by deficiency or hyposecretion of Insulin (produced by β-cells of pancreas). Characterized by high blood glucose level (hyperglycemia), presence of glucose in urine (glycosuria), and presence of ketone bodies.
• Diabetes Insipidus: Caused by deficiency or hyposecretion of Vasopressin / ADH (released by posterior pituitary). Characterized by excretion of large volumes of dilute urine (polyuria) and extreme thirst, without high blood sugar levels or glucose in urine.
Textbook Chapter End Exercise Questions
| Feature | Hyperthyroidism | Hypothyroidism |
|---|---|---|
| Secretion Level | Excessive synthesis and secretion of thyroid hormones (T₃ & T₄). | Deficient synthesis and secretion of thyroid hormones. |
| Metabolic Rate (BMR) | Significantly increases Basal Metabolic Rate (BMR). | Decreases Basal Metabolic Rate (BMR). |
| Associated Conditions | Grave's Disease (Exophthalmic Goitre), weight loss, protrusion of eyeballs, rapid heart rate. | Simple Goitre, Cretinism (in infants), Myxedema (in adults), weight gain, lethargy. |
| Feature | Exocrine Glands | Endocrine Glands |
|---|---|---|
| Ducts | Possess ducts to carry secretions to target site. | Ductless glands; secretions released directly into bloodstream. |
| Secretory Product | Secrete enzymes, saliva, sweat, mucus, milk, digestive juices. | Secrete non-nutrient chemical messengers called Hormones. |
| Target Location | Secretions act locally or on near epithelial surfaces. | Hormones travel through blood to act on distant target organs. |
| Examples | Salivary glands, Sweat glands, Liver, Gastric glands. | Pituitary gland, Thyroid gland, Adrenal gland, Parathyroid gland. |
Read More & Chapter Resources
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