Complete Solutions and Summary of Chemical Coordination and Integration – NCERT Class 11, Biology, Chapter 19 – Summary, Questions, Answers, Extra Questions

Summary of hormones, endocrine glands, mechanisms of hormone action, feedback control, and integration of body functions with NCERT questions.

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Categories: NCERT, Class XI, Biology, Summary, Hormones, Endocrine System, Hormone Action, Feedback Mechanisms, Chapter 19

Tags: Hormones, Endocrine Glands, Chemical Coordination, Feedback Control, Pituitary, Adrenal, Thyroid, Pancreas, Hormone Mechanism, NCERT, Class 11, Biology, Chapter 19, Answers, Extra Questions

Chemical Coordination and Integration Class 11 NCERT Chapter 19 - Ultimate Study Guide, Notes, Questions, Quiz 2025

Full Chapter Summary & Detailed Notes - Chemical Coordination and Integration Class 11 NCERT

Overview & Key Concepts

Chapter Goal: Understand the endocrine system, hormones, and their role in coordination alongside the neural system. Exam Focus: Glands, hormones, functions, disorders, mechanism of action. 2025 Updates: Emphasis on hormonal imbalances and therapies. Fun Fact: Hormones act in trace amounts but regulate major body functions like growth and metabolism. Core Idea: Endocrine system provides long-term, widespread coordination via hormones. Real-World: Insulin therapy for diabetes, stress response via adrenaline.
Wider Scope: Links to human physiology, reproduction, metabolism, and diseases like diabetes and goitre.

19.1 Endocrine Glands and Hormones

The neural system offers point-to-point rapid coordination, but it's short-lived and doesn't reach all cells. Cellular functions require continuous regulation, handled by hormones from the endocrine system.
Endocrine glands are ductless; secretions (hormones) enter blood directly. Classical definition: Chemicals from glands transported to distant targets. Modern: Non-nutrient intercellular messengers in trace amounts.
Includes molecules beyond classical glands. Invertebrates: Simple systems with few hormones. Vertebrates: Complex, many chemicals as hormones. Focus: Human endocrine system.
Key Point: Neural and endocrine systems jointly regulate physiology.

19.2 Human Endocrine System

Comprises glands (pituitary, pineal, thyroid, etc.) and hormone-producing tissues (GI tract, liver, etc.). Figure 19.1 shows locations.

19.2.1 The Hypothalamus

Basal forebrain part; regulates body functions via neurosecretory nuclei producing hormones.
Hormones: Releasing (e.g., GnRH stimulates gonadotrophins) and inhibiting (e.g., somatostatin inhibits GH).
Anterior pituitary regulated via portal system; posterior via neural control (Figure 19.2).
Role: Links neural and endocrine coordination.

19.2.2 The Pituitary Gland

In sella turcica, attached to hypothalamus. Divided: Adenohypophysis (anterior: pars distalis, intermedia) and neurohypophysis (posterior).
Anterior (pars distalis): GH (growth), PRL (milk), TSH (thyroid), ACTH (adrenal), LH/FSH (gonads).
Pars intermedia: MSH (pigmentation).
Posterior: Oxytocin (uterus contraction, milk ejection), Vasopressin/ADH (water reabsorption; deficiency: Diabetes insipidus).
Disorders: GH excess (gigantism/acromegaly), deficiency (dwarfism). LH/FSH: Gonadal activity, spermatogenesis, ovulation.
Key: Master gland, regulated by hypothalamus.

19.2.3 The Pineal Gland

Dorsal forebrain; secretes melatonin.
Regulates 24-hour rhythms (sleep-wake, temperature); influences metabolism, pigmentation, menstrual cycle, immunity.

19.2.4 Thyroid Gland

Two lobes on trachea (Figure 19.3); follicles produce T3/T4 (thyroxine, needs iodine).
Functions: Basal metabolic rate, RBC formation, metabolism of carbs/proteins/fats, water/electrolyte balance.
Also: Thyrocalcitonin (TCT) lowers blood Ca2+.
Disorders: Iodine deficiency (goitre, cretinism in pregnancy); hyperthyroidism (Graves' disease: exophthalmic goitre, weight loss).

19.2.5 Parathyroid Gland

Four glands behind thyroid (Figure 19.3); secrete PTH (peptide).
Regulated by blood Ca2+; increases Ca2+ via bone resorption, renal reabsorption, gut absorption.
Hypercalcemic hormone; balances with TCT.

19.2.6 Thymus

Lobular, between lungs; secretes thymosins.
Role: T-lymphocyte differentiation (cell-mediated immunity), antibody production (humoral).
Degenerates with age, weakening immunity in elderly.

19.2.7 Adrenal Gland

Pair above kidneys (Figure 19.4); cortex (outer) and medulla (inner).
Medulla: Adrenaline/noradrenaline (catecholamines; fight/flight: alertness, heart rate, glycogenolysis).
Cortex layers: Glomerulosa (mineralocorticoids: aldosterone - Na+/water reabsorption), fasciculata/reticularis (glucocorticoids: cortisol - gluconeogenesis, anti-inflammatory; androgens).
Disorder: Addison's (cortex underproduction: weakness).

19.2.8 Pancreas

Composite (exocrine/endocrine); islets: α-cells (glucagon: hyperglycemia via glycogenolysis/gluconeogenesis), β-cells (insulin: hypoglycemia via uptake/glycogenesis).
Balance blood glucose; deficiency: Diabetes mellitus (ketone bodies, urine glucose).

19.2.9 Testis

In scrotum; Leydig cells produce androgens (testosterone).
Functions: Male accessory organs, secondary characters (hair, voice), spermatogenesis, libido, anabolic effects.

19.2.10 Ovary

In abdomen; follicles produce estrogen (growth of accessories, secondary characters, behavior), corpus luteum produces progesterone (pregnancy, mammary alveoli).

19.3 Hormones of Heart, Kidney and Gastrointestinal Tract

Heart: Atrial natriuretic factor (ANF) lowers BP via vasodilation.
Kidney: Erythropoietin stimulates RBC formation.
GI Tract: Gastrin (HCl/pepsinogen), secretin (pancreatic water/bicarbonate), CCK (enzymes/bile), GIP (inhibits gastric secretion).
Other: Growth factors for tissue growth/repair.

19.4 Mechanism of Hormone Action

Hormones bind specific receptors (membrane-bound or intracellular/nuclear).
Peptide/protein/amino acid derivatives: Second messengers (cAMP, IP3, Ca2+) regulate metabolism (Figure 19.5a).
Steroids/iodothyronines: Enter cell, bind nuclear receptors, regulate gene expression (Figure 19.5b).
Groups: Peptides (insulin), steroids (cortisol), iodothyronines (T3/T4), amino derivatives (epinephrine).

Summary

Hormones provide chemical coordination; endocrine system includes major glands and tissues.
Pituitary: Trophic hormones; thyroid: Metabolism; parathyroid/thymus: Ca2+/immunity; adrenal: Stress/response; pancreas: Glucose; gonads: Reproduction.
Other organs: ANF, erythropoietin, GI hormones. Mechanism: Receptor binding leads to responses.

Why This Guide Stands Out

Complete coverage: All glands, disorders, mechanisms. Exam-ready with detailed notes, Q&A, quiz. Free & ad-free for 2025 boards.

Key Themes & Tips

Coordination: Neural (fast) vs. Endocrine (sustained).
Disorders: Gigantism, diabetes, goitre.
Tip: Memorize gland-hormone pairs with functions; draw Figure 19.1 for locations.

Exam Case Studies

Questions on pituitary disorders, hormone mechanisms, thyroid functions.

Project & Group Ideas

Model endocrine system; discuss diabetes management.

Key Definitions & Terms - Complete Glossary

All terms from chapter; easy to memorize. Detailed explanations for each. Expanded for depth: Over 20 key terms with examples, functions, and relevance.

Endocrine Gland

Ductless glands secreting hormones into blood. Example: Pituitary. Function: Long-term regulation. Relevance: Coordinate body functions beyond neural reach. Disorder: Tumors cause overproduction.

Hormone

Non-nutrient chemical messengers in trace amounts. Example: Insulin. Function: Intercellular signaling. Relevance: Regulate metabolism, growth. Modern view includes non-gland sources.

Releasing Hormone

Stimulates pituitary secretion. Example: GnRH. Function: Triggers gonadotrophins. Relevance: Controls reproduction. From hypothalamus nuclei.

Inhibiting Hormone

Inhibits pituitary secretion. Example: Somatostatin (GH). Function: Prevents overproduction. Relevance: Balances growth. Neural origin.

Growth Hormone (GH)

From anterior pituitary. Function: Body growth. Excess: Gigantism/acromegaly. Deficiency: Dwarfism. Regulated by hypothalamus.

Prolactin (PRL)

Anterior pituitary. Function: Mammary growth, milk production. Relevance: Lactation post-pregnancy.

Thyroid Stimulating Hormone (TSH)

Anterior pituitary. Function: Stimulates thyroid T3/T4. Relevance: Metabolism control.

Adrenocorticotrophic Hormone (ACTH)

Anterior pituitary. Function: Adrenal glucocorticoids. Relevance: Stress response.

Gonadotrophins (LH/FSH)

Anterior pituitary. Function: Gonadal activity, gametogenesis. Relevance: Reproduction.

Melanocyte Stimulating Hormone (MSH)

Pars intermedia. Function: Skin pigmentation. Relevance: Melanocyte regulation.

Oxytocin

Posterior pituitary (hypothalamic origin). Function: Uterus contraction, milk ejection. Relevance: Parturition, lactation.

Vasopressin/ADH

Posterior pituitary. Function: Water reabsorption in kidneys. Deficiency: Diabetes insipidus. Relevance: Osmoregulation.

Melatonin

Pineal gland. Function: Diurnal rhythms (sleep-wake). Relevance: Circadian control, immunity.

Thyroxine (T4)/Triiodothyronine (T3)

Thyroid. Function: Basal metabolism, growth. Iodine essential. Disorder: Goitre (deficiency).

Thyrocalcitonin (TCT)

Thyroid. Function: Lowers blood Ca2+. Relevance: Calcium balance with PTH.

Parathyroid Hormone (PTH)

Parathyroid. Function: Raises blood Ca2+ (bone resorption). Relevance: Hypercalcemic, homeostasis.

Thymosins

Thymus. Function: T-cell maturation, immunity. Relevance: Degenerates with age.

Adrenaline/Noradrenaline

Adrenal medulla. Function: Fight/flight (heart rate, glycogenolysis). Relevance: Emergency hormones.

Glucocorticoids (Cortisol)

Adrenal cortex. Function: Gluconeogenesis, anti-inflammatory. Relevance: Stress, metabolism.

Mineralocorticoids (Aldosterone)

Adrenal cortex. Function: Na+/water retention. Relevance: Electrolyte balance.

Insulin

Pancreas β-cells. Function: Lowers blood glucose (uptake). Deficiency: Diabetes mellitus.

Glucagon

Pancreas α-cells. Function: Raises blood glucose (glycogenolysis). Relevance: Glucose homeostasis.

Androgens (Testosterone)

Testis. Function: Male secondary characters, spermatogenesis. Relevance: Puberty, libido.

Estrogen/Progesterone

Ovary. Function: Female characters, pregnancy support. Relevance: Menstrual cycle, lactation.

Atrial Natriuretic Factor (ANF)

Heart. Function: Lowers BP (vasodilation). Relevance: Pressure regulation.

Erythropoietin

Kidney. Function: RBC formation. Relevance: Oxygen transport.

Gastrin/Secretin/CCK/GIP

GI tract. Function: Digestion (acid, enzymes, bile). Relevance: Nutrient absorption.

Second Messenger

Intracellular signals (cAMP, Ca2+). Function: Amplifies hormone effects. Relevance: Peptide hormone action.

Receptor

Target proteins for hormones. Types: Membrane/intracellular. Relevance: Specificity in action.

Tip: Group by gland; use flashcards for disorders. This glossary covers all NCERT terms with examples for retention.

Additional Depth: Hormones are classified chemically (peptides, steroids, etc.), affecting action mechanisms. Trace amounts suffice due to high affinity. Feedback loops (e.g., TSH-TH feedback) maintain balance. Evolutionary: Simple in invertebrates, complex in humans for homeostasis.

Real-Life: Hormone therapies (e.g., insulin injections) mimic natural regulation. Disruptions from pollution affect endocrine health.

60+ Questions & Answers - NCERT Based (Class 11)

Structured as Part A (1 mark, short answers), Part B (4 marks, ~6 lines/medium length), Part C (8 marks, detailed/long). 20 per part, based on chapter, answers matching scheme.

Part A: 1 Mark Questions (Short Answers)

1. What is an endocrine gland?

1 Mark Answer: Ductless gland secreting hormones into blood.

2. Modern definition of hormone?

1 Mark Answer: Non-nutrient intercellular messenger in trace amounts.

3. Hypothalamus hormones types?

1 Mark Answer: Releasing and inhibiting.

4. Example of releasing hormone?

1 Mark Answer: GnRH.

5. Pituitary divided into?

1 Mark Answer: Adenohypophysis and neurohypophysis.

6. GH excess causes?

1 Mark Answer: Gigantism.

7. ADH function?

1 Mark Answer: Water reabsorption.

8. Pineal hormone?

1 Mark Answer: Melatonin.

9. Thyroid hormones?

1 Mark Answer: T3, T4.

10. Iodine deficiency causes?

1 Mark Answer: Goitre.

11. PTH function?

1 Mark Answer: Increases blood Ca2+.

12. Thymus secretes?

1 Mark Answer: Thymosins.

13. Adrenal medulla hormones?

1 Mark Answer: Adrenaline, noradrenaline.

14. Cortisol is?

1 Mark Answer: Glucocorticoid.

15. Aldosterone function?

1 Mark Answer: Na+ reabsorption.

16. Insulin from?

1 Mark Answer: β-cells.

17. Glucagon effect?

1 Mark Answer: Hyperglycemia.

18. Testis hormone?

1 Mark Answer: Testosterone.

19. Ovary hormones?

1 Mark Answer: Estrogen, progesterone.

20. ANF from?

1 Mark Answer: Heart.

Part B: 4 Marks Questions (Medium Length Answers ~6 Lines)

1. Differentiate neural and endocrine coordination.

4 Marks Answer: Neural: Point-to-point, rapid, short-lived via nerve fibers. Doesn't innervate all cells. Endocrine: Widespread, slow, long-lasting via hormones in blood. Jointly regulate physiology. Neural for quick responses; endocrine for sustained. Example: Adrenaline (neural trigger, hormonal effect).

2. Explain hypothalamus role.

4 Marks Answer: Basal forebrain; neurosecretory nuclei produce releasing/inhibiting hormones. Regulate pituitary: GnRH stimulates gonadotrophins; somatostatin inhibits GH. Anterior via portal system; posterior neural. Links neural-endocrine. Wide body function spectrum.

3. Describe pituitary structure and hormones.

4 Marks Answer: In sella turcica; anterior (adenohypophysis: GH, PRL, TSH, ACTH, LH/FSH), intermediate (MSH), posterior (oxytocin, ADH from hypothalamus). Functions: Growth, lactation, thyroid/adrenal/gonadal stimulation. Disorders: Gigantism, diabetes insipidus.

4. Functions of thyroid hormones.

4 Marks Answer: T3/T4 regulate basal metabolism, RBC formation, carb/protein/fat metabolism, water balance. TCT lowers Ca2+. Iodine essential; deficiency: Goitre/cretinism. Hyper: Graves' disease (weight loss, exophthalmos).

5. Role of PTH and TCT.

4 Marks Answer: PTH (parathyroid): Raises Ca2+ via bone resorption, renal/gut absorption. Hypercalcemic. TCT (thyroid): Lowers Ca2+. Together maintain calcium homeostasis. Regulated by blood Ca2+ levels.

6. Adrenal gland functions.

4 Marks Answer: Medulla: Catecholamines for fight/flight (heart rate, glycogenolysis). Cortex: Glucocorticoids (cortisol: metabolism, anti-inflammatory), mineralocorticoids (aldosterone: electrolytes), androgens (puberty hair). Addison's: Weakness.

7. Pancreas as endocrine gland.

4 Marks Answer: Islets: α-glucagon (hyperglycemia: glycogenolysis), β-insulin (hypoglycemia: uptake/glycogenesis). Maintain glucose homeostasis. Diabetes: Insulin deficiency, ketone bodies.

8. Gonadal hormones in males.

4 Marks Answer: Testis: Androgens (testosterone) from Leydig cells. Develop accessories, secondary characters, spermatogenesis, libido, anabolic effects.

9. Gonadal hormones in females.

4 Marks Answer: Ovary: Estrogen (follicles: accessories, characters), progesterone (corpus luteum: pregnancy, mammary). Regulate cycle, behavior.

10. GI tract hormones.

4 Marks Answer: Gastrin (HCl), secretin (bicarbonate), CCK (enzymes/bile), GIP (inhibits secretion). Aid digestion, absorption.

11. Second messenger role.

4 Marks Answer: For membrane receptors (peptides): cAMP/IP3/Ca2+ amplify signals, regulate metabolism without hormone entry.

12. Steroid hormone action.

4 Marks Answer: Enter cell, bind nuclear receptors, regulate gene expression for protein synthesis, physiological effects.

13. Diabetes mellitus cause.

4 Marks Answer: Insulin deficiency/resistance; hyperglycemia, glucosuria, ketonuria. Treated with insulin.

14. Thymus importance.

4 Marks Answer: Thymosins for T-cell immunity (cell-mediated, humoral). Degenerates, weakens elderly immunity.

15. ANF function.

4 Marks Answer: From heart atria; lowers BP via vessel dilation when pressure high.

16. Erythropoietin source.

4 Marks Answer: Kidney juxtaglomerular cells; stimulates erythropoiesis.

17. Acromegaly symptom.

4 Marks Answer: GH excess in adults; facial disfigurement.

18. Cretinism cause.

4 Marks Answer: Hypothyroidism in pregnancy; stunted growth, mental retardation.

19. Oxytocin role in females.

4 Marks Answer: Uterus contraction at birth, milk ejection.

20. Hyperthyroidism form.

4 Marks Answer: Exophthalmic goitre/Graves' disease.

Part C: 8 Marks Questions (Detailed Long Answers)

1. Describe human endocrine system overview.

8 Marks Answer: Endocrine system: Ductless glands (pituitary, thyroid, etc.) and tissues (GI, heart) secrete hormones for coordination. Neural: Fast/point-specific; endocrine: Slow/widespread/sustained. Joint regulation of physiology. Hypothalamus links via releasing/inhibiting hormones to pituitary (master gland). Major glands: Pineal (rhythms), thyroid (metabolism), parathyroid (Ca2+), thymus (immunity), adrenal (stress), pancreas (glucose), gonads (reproduction). Other: ANF (BP), erythropoietin (RBC), GI (digestion). Hormones: Trace, specific receptors. Disorders: Imbalances like diabetes, goitre. Evolutionary: Complex in vertebrates for homeostasis. Figure 19.1 locations essential for diagrams.

2. Explain pituitary gland in detail.

8 Marks Answer: Attached to hypothalamus in sella turcica; adenohypophysis (anterior: pars distalis GH/PRL/TSH/ACTH/LH/FSH for growth/lactation/thyroid/adrenal/gonads; pars intermedia MSH pigmentation) and neurohypophysis (posterior: oxytocin milk ejection/uterus contraction, ADH water reabsorption - deficiency diabetes insipidus). Regulated by hypothalamic portal/neural. Disorders: GH excess gigantism (child)/acromegaly (adult - facial changes, complications); low dwarfism. LH/FSH: Males spermatogenesis/androgens; females ovulation/corpus luteum/FSH follicles. ACTH glucocorticoids. PRL mammary. Hard to diagnose early acromegaly. Key trophic role.

3. Discuss thyroid and parathyroid glands.

8 Marks Answer: Thyroid: Two lobes on trachea (isthmus); follicles synthesize T3/T4 (iodine needed) for BMR, RBC, metabolism, balance; TCT lowers Ca2+. Deficiency: Hypothyroidism - goitre (enlargement), cretinism (pregnancy: stunted/mental issues), irregular menses. Hyper: Cancer/nodules - Graves' (protruding eyes, high BMR, loss). Parathyroid: Four behind thyroid; PTH peptide raises Ca2+ (bones dissolve, renal/gut absorption) - hypercalcemic, balances TCT. Regulated by Ca2+ levels. Both crucial homeostasis; iodine diet prevents goitre. Figures 19.3a/b show positions.

4. Elaborate adrenal gland functions and disorders.

8 Marks Answer: Pair above kidneys; medulla (central: adrenaline/noradrenaline catecholamines - emergency/fight/flight: alertness, dilation, sweating, heart/respiration up, glycogen/lipid/protein breakdown). Cortex (outer layers: glomerulosa mineralocorticoids aldosterone Na+/water retain/excrete K+ for BP/volume; fasciculata glucocorticoids cortisol gluconeogenesis/lipolysis/proteolysis, anti-inflammatory, RBC, CV/kidney; reticularis androgens puberty hair). Addison's: Cortex low - weakness/fatigue from carb issues. Figure 19.4 shows structure. Stress response key; cortisol suppresses immunity.

5. Explain pancreas role in glucose regulation.

8 Marks Answer: Composite gland; endocrine islets (1-2% tissue: α-glucagon hyperglycemia via liver glycogenolysis/gluconeogenesis/reduced uptake; β-insulin hypoglycemia via hepatocyte/adipocyte uptake/glycogenesis). Homeostasis: Antagonistic balance. Prolonged high glucose: Diabetes mellitus - glucosuria, ketonemia (harmful bodies), treated insulin. Islets ~1-2 million. Deficiency/resistance complex; urine loss, complications. Essential for metabolism; links to nutrition/diet.

6. Describe gonadal hormones and functions.

8 Marks Answer: Testis: Dual (seminiferous tubules sperm, Leydig androgens testosterone - accessories epididymis/vas/seminal/prostate, secondary hair/voice/aggression, spermatogenesis, libido, anabolic protein/carb). Ovary: Follicles estrogen (accessories/follicles growth, secondary voice/breast, behavior); post-ovulation corpus luteum progesterone (pregnancy maintenance, mammary alveoli/milk). Regulate reproduction/puberty. Figure 19.1 positions. Disruptions: Infertility, PCOS.

7. Hormones from non-endocrine organs.

8 Marks Answer: Heart: ANF peptide from atria lowers BP (vessel dilation on high pressure). Kidney: Juxtaglomerular erythropoietin for RBC (erythropoiesis). GI: Endocrine cells - gastrin gastric HCl/pepsinogen, secretin exocrine pancreas water/bicarbonate, CCK pancreas enzymes/gallbladder bile, GIP inhibits gastric motility/secretion. Growth factors from tissues for repair/growth. Broaden hormone concept; aid digestion, hematopoiesis, pressure. Essential integration.

8. Mechanism of hormone action in detail.

8 Marks Answer: Bind specific target receptors (membrane for peptides/derivatives; intracellular/nuclear for steroids/thyroid). Complex formation: Biochemical changes regulate metabolism/physiology. Peptides (insulin/glucagon/pituitary): Don't enter, generate second messengers (cAMP/IP3/Ca2+) for responses (Figure 19.5a). Steroids (cortisol/testosterone): Enter, nuclear bind, gene expression/chromosome function for proteins/differentiation (Figure 19.5b). Groups: Peptides, steroids, iodothyronines, amino derivatives. Specificity: One hormone per receptor. Cumulative effects developmental.

9. Discuss endocrine disorders.

8 Marks Answer: Gigantism/dwarfism (GH), acromegaly (adult GH excess - face issues), diabetes insipidus (ADH low - dehydration), goitre/cretinism (thyroid low - iodine), Graves' (thyroid high - eyes/BMR), Addison's (adrenal cortex low - fatigue), diabetes mellitus (insulin - glucose/ketones). Causes: Deficiency/excess, cancer, pregnancy. Treatments: Supplements (iodine/insulin), therapy. Impact: Growth, metabolism, immunity. Early diagnosis key; e.g., acromegaly undetected years.

10. Role of thymus and pineal glands.

8 Marks Answer: Thymus: Behind sternum, lobular; thymosins differentiate T-lymphocytes (cell-mediated/humoral immunity via antibodies). Major immune development; degenerates old age - weak responses. Pineal: Dorsal forebrain; melatonin regulates 24-hr rhythms (sleep-wake, temperature), influences metabolism/pigmentation/menstrual/defense. Circadian key; light-sensitive. Both specialized: Immunity rhythms. Age-related decline thymus; pineal seasonal effects.

11. Compare glucocorticoids and mineralocorticoids.

8 Marks Answer: Both adrenal cortex; glucocorticoids (cortisol main): Carb metabolism (gluconeogenesis/lipolysis/proteolysis, inhibit amino uptake), maintain CV/kidney, anti-inflammatory/suppress immunity, stimulate RBC. Mineralocorticoids (aldosterone): Renal Na+/water reabsorb, K+/phosphate excrete; maintain electrolytes/fluid/osmotic/BP. Layers: Fasciculata/reticularis glucocorticoids, glomerulosa mineralocorticoids. Stress: Cortisol up; volume: Aldosterone. Androgens minor. Addison's affects both.

12. Explain feedback in hormone regulation.

8 Marks Answer: Hypothalamus-pituitary axis: Releasing hormones stimulate pituitary tropic (TSH/ACTH/LH/FSH) which target glands (thyroid/adrenal/gonads) feedback inhibit. E.g., High T3/T4 inhibit TSH/GnRH. Ca2+ regulates PTH/TCT. Glucose: Insulin/glucagon antagonistic. ADH: Osmolarity. Ensures balance; disruptions cause disorders like hyperthyroidism. Negative feedback common; positive rare (ovulation). Evolutionary for homeostasis.

13. Significance of trace hormone amounts.

8 Marks Answer: High receptor affinity amplifies signals via second messengers/gene expression. E.g., Insulin trace lowers glucose rapidly. Efficiency: No waste, specific. Disorders from imbalance show potency. Modern definition emphasizes. Vs. nutrients: Messengers, not energy. Trace enables fine control; excess toxicity.

14. Hormones in reproduction.

8 Marks Answer: Hypothalamus GnRH → pituitary LH/FSH → gonads. Males: FSH/androgens spermatogenesis; LH testosterone. Females: FSH follicles/estrogen; LH ovulation/corpus/progesterone. Oxytocin labor/milk. Progesterone pregnancy. Estrogen characters/behavior. Disruptions: Infertility. Cycle: Feedback loops.

15. Digestion hormones overview.

8 Marks Answer: GI peptides: Gastrin stimulates gastric HCl/pepsinogen for protein digestion. Secretin: Pancreatic bicarbonate neutralizes acid. CCK: Pancreatic enzymes (proteases/lipases/amylase), gallbladder bile for fats. GIP: Inhibits gastric to slow, allows absorption. Coordinate phases: Cephalic/gastric/intestinal. Essential breakdown/absorption; disorders like ulcers from imbalance.

16. Compare membrane and intracellular receptors.

8 Marks Answer: Membrane (peptides/derivatives): Hormone binds outside, second messengers (cAMP/Ca2+) inside for quick metabolism changes. Intracellular/nuclear (steroids/thyroid): Hormone enters, binds, gene expression for long-term growth/differentiation. Specificity: One per hormone. Figures 19.5a/b illustrate. Determines action speed/type.

17. Impact of endocrine on immunity/metabolism.

8 Marks Answer: Thymosins: T-cells/immunity. Cortisol: Suppresses inflammation/immune. Thyroid: Metabolism/RBC. Insulin/glucagon: Glucose. PTH/TCT: Ca2+ for bones/cells. Melatonin: Defense. Interlinks: Stress weakens immunity via cortisol. Metabolism: Thyroid/adrenal/pancreas core. Disorders: Autoimmune (Graves'), metabolic (diabetes).

18. Evolutionary aspects of endocrine system.

8 Marks Answer: Invertebrates: Simple, few hormones (ecdysone). Vertebrates: Complex, many (pituitary axis). Human: Integrated with neural for homeostasis. Adaptations: Stress hormones survival, reproduction continuity. Molecular: Similar receptors across species. Future: Endocrine disruptors (plastics) challenge.

19. Therapeutic uses of hormones.

8 Marks Answer: Insulin: Diabetes control. Thyroxine: Hypothyroidism. Cortisol: Inflammation (asthma). Contraceptives: Estrogen/progesterone. GH: Dwarfism. Erythropoietin: Anemia. Challenges: Side effects (weight gain), dependency. Research: Targeted delivery.

20. Integration of systems.

8 Marks Answer: Hypothalamus bridges neural-endocrine. Pituitary tropic links glands. Feedback loops. E.g., Stress: Neural → hypothalamus → ACTH → cortisol. Reproduction: GnRH-LH-FSH-gonads. Digestion: Neural-GI hormones. Ensures holistic response; disruptions systemic diseases.

Practice Tip: Diagrams for glands; link disorders to hormones.

Key Concepts

Core ideas from the chapter, explained in detail. Expanded with examples, diagrams references, real-life ties for depth (equivalent to 3+ pages).

Endocrine vs. Neural Coordination

Neural: Electrical, synaptic, fast/short (e.g., reflex). Endocrine: Chemical, blood-borne, slow/long (e.g., growth). Integration: Hypothalamus uses both. Real-life: Adrenaline rush (neural trigger, hormonal sustain). Importance: All cells regulated, unlike nerves. Disorders: Imbalance leads to systemic issues like hypertension.

Hypothalamic-Pituitary Axis

Master control: Releasing/inhibiting to pituitary tropins. Portal system for anterior. Example: GnRH-LH surge ovulation. Feedback negative. Ties to reproduction/stress. Diagram: Figure 19.2. Clinical: Tumors disrupt axis, causing infertility.

Hormone Classification & Action

Chemical: Peptides (insulin - second messengers), steroids (cortisol - gene expression). Trace potency via affinity. Specificity: Receptors target only. Examples: cAMP in FSH action. Real: Hormone replacement therapy mimics.

Metabolic Regulation

Thyroid/adrenal/pancreas core. Thyroid BMR, cortisol gluconeogenesis, insulin/glucagon glucose. Homeostasis via antagonism. Diabetes: Modern epidemic, lifestyle links. Iodine campaigns prevent goitre globally.

Reproductive Endocrinology

GnRH-LH/FSH-estrogen/progesterone/testosterone cycle. Puberty triggers, menstrual feedback. Oxytocin labor. IVF uses hormone stimulation. Gender differences: Androgens aggression, estrogens behavior.

Stress & Emergency Response

HPA axis: Hypothalamus-CRH-ACTH-cortisol. Adrenaline immediate. Chronic stress: Immunity down, diseases up. Evolutionary: Survival advantage. Modern: Meditation modulates.

Use in: Essays on integration, MCQs on functions. Depth: Feedback loops prevent overload; e.g., high cortisol inhibits CRH. Global health: Endocrine disruptors in plastics mimic estrogen, cause issues.

Additional: Immunity-thymus/cortisol balance; aging degenerates thymus, cortisol rises. Calcium: PTH/TCT dynamic for bones/teeth. Rhythms: Melatonin jet lag therapy.

Interlinks: GI hormones with neural (vagus) for digestion; erythropoietin with kidney function in anemia.

Principles of Hormone Action - Detailed Explanations

Key principles with examples. Expanded: Mechanisms, classifications, regulations (3+ pages worth).

Principle: Specificity & Receptors

Hormone binds only specific target receptors (membrane/intracellular). Ensures precise action. Example: Insulin hepatocytes only. Lock-key model. Mutations cause resistance (diabetes type 2). Amplification: One bind → many signals.

Principle: Second Messenger System

Peptide hormones: Bind membrane, activate G-proteins → cAMP/IP3/Ca2+ cascades. Quick, no entry. Example: FSH ovarian growth via cAMP. Vs. Steroids: Slow gene via nuclear. Diagram 19.5a.

Principle: Gene Expression Regulation

Steroids/thyroid: Complex to DNA, transcribe mRNA → proteins. Long-term. Example: Estrogen mammary development. Feedback integrates.

Principle: Feedback Mechanisms

Negative: Product inhibits release (TSH-TH). Positive: Rare (LH surge). Maintains levels. Disruptions: Hypersecretion diseases.

Principle: Trace Amounts Efficacy

Affinity high; cascades amplify. Example: pg/mL melatonin rhythms. Efficiency for homeostasis.

Principle: Chemical Diversity

Peptides (insulin), steroids (progesterone), iodothyronines (T4), amines (adrenaline). Dictates solubility/action. Water-soluble: Membrane; lipid: Intracellular.

Tip: Compare actions in table. Depth: G-protein cycle (activate/inactivate). IP3 releases Ca2+ stores. Steroid chaperones aid nuclear entry. Clinical: Agonists/antagonists drugs (e.g., tamoxifen estrogen block).

Regulations: Tropic chains (hypothalamus → pituitary → gland). Rhythms: Pulsatile GnRH. Environment: Stress up cortisol. Evolutionary: Conserved pathways across phyla.

Applications: Signal transduction research for cancer (growth factors).

All Textbook Examples - Step by Step Solutions

Chapter illustrative cases: Disorders, mechanisms. Expanded with steps.

Example: Gigantism/Acromegaly (GH)

Step 1: Hypothalamus low somatostatin. Step 2: High GH secretion. Step 3: Child: Gigantism (tall). Adult: Acromegaly (face/hands). Step 4: Complications (heart). Treatment: Surgery.

Example: Diabetes Insipidus (ADH)

Step 1: Hypothalamus/synthesis issue. Step 2: Low ADH storage/release. Step 3: Kidney poor water conserve. Step 4: Dehydration/polyuria. Treatment: Desmopressin.

Example: Goitre/Cretinism (Thyroid)

Step 1: Iodine deficiency. Step 2: Low T3/T4. Step 3: TSH up → enlargement (goitre). Pregnancy: Fetus cretinism (growth/mental). Step 4: Iodine supplements.

Example: Diabetes Mellitus (Insulin)

Step 1: β-cell destruction/resistance. Step 2: High glucose. Step 3: Glucosuria/ketones. Step 4: Therapy insulin/diet. Types 1/2.

Example: Addison's (Adrenal)

Step 1: Cortex damage. Step 2: Low cortisol/aldosterone. Step 3: Weakness/fatigue/electrolyte imbalance. Step 4: Replacement therapy.

Figure 19.5: Hormone Mechanism

(a) Peptide: Bind → G-protein → cAMP → response. (b) Steroid: Enter → nuclear → transcription → protein → effect. Steps amplify specificity.

Tip: Use for disorder essays. Depth: Acromegaly: 5-10 years undetected; MRI diagnosis. Diabetes: HbA1c monitor. Historical: Banting's dog experiments.

Other: Graves' autoimmunity; PTH hyperparathyroidism bones.

Quick Revision Notes & Mnemonics - Exam-Ready

19.1 Endocrine Glands/Hormones

Ductless; hormones: Messengers trace. Inverts simple; verts complex.

19.2.1 Hypothalamus

Releasing (GnRH), inhibiting (somatostatin). Portal anterior.

19.2.2 Pituitary

Ant: GH/PRL/TSH/ACTH/LH/FSH. Post: Oxytocin/ADH. Disorders: Giant/dwarf.

19.2.3 Pineal

Melatonin: Rhythms, metabolism.

19.2.4 Thyroid

T3/T4: Metabolism; TCT: Ca down. Goitre/Graves.

19.2.5 Parathyroid

PTH: Ca up. Balance TCT.

19.2.6 Thymus

Thymosins: T-cells, immunity. Ages degenerates.

19.2.7 Adrenal

Med: Adrenaline fight. Cort: Cortisol (gluco), aldosterone (mineral). Addison.

19.2.8 Pancreas

Insulin down glucose; glucagon up. Diabetes.

19.2.9 Testis

Testosterone: Male chars, sperm.

19.2.10 Ovary

Estrogen chars; progesterone pregnancy.

19.3 Other Hormones

ANF BP down; erythropoietin RBC; GI: Gastrin etc digestion.

19.4 Mechanism

Peptide: 2nd mess (cAMP). Steroid: Gene expr.

Mnemonics: Pituitary Ant: "Goats Produce Tall And Curly Long Fleecy" (GH PRL TSH ACTH LH FSH). Hierarchy none, but glands: "Happy Penguins Take Pictures Through A Panoramic Telescope Of Various Oceans" (Hypo Pineal Thy Parathy Thym Adren Pan Testis Ovary).

Tip: Tables for hormones/functions/disorders. All subtopics covered for quick scan.

This article has been published in CBSE Class 11 Annual Assessment. Explore everything related to it here.

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