Chemical Coordination and Integration Class 11 Biology: Endocrine Glands, Hormones and Disorders

What Chemical Coordination and Integration is about

Weightage: This chapter is part of Unit V, Human Physiology, which carries 18 of the 70 theory marks in the school annual exam together with Breathing and Exchange of Gases, Body Fluids and Circulation, Excretory Products and their Elimination, Locomotion and Movement and Neural Control and Coordination.Source: CBSE Biology (044) syllabus 2026-27, Class XI course structure, Unit V Human Physiology

Key concepts

Endocrine glands, hormones and the hypothalamus

NCERT section 19.1 Endocrine Glands and Hormones; 19.2 Human Endocrine System (19.2.1 The Hypothalamus)

Endocrine vs exocrine glands:

• Endocrine: no ducts; secretions (hormones) go into blood, e.g. thyroid, pituitary.
• Exocrine: have ducts carrying secretions to a surface or cavity, e.g. salivary glands, sweat glands.

Hormones: non-nutrient chemicals acting as intercellular messengers, produced in trace amounts. Their effects can be developmental, metabolic or behavioural.

Hypothalamus (basal part of the diencephalon, forebrain):

• Regulates a wide spectrum of body functions.
• Contains several groups of neurosecretory cells (nuclei) that make hormones.
• These hormones regulate the synthesis and secretion of pituitary hormones. Two types:
• Releasing hormones: stimulate pituitary secretion. Example: gonadotrophin releasing hormone (GnRH) stimulates the pituitary to make and release gonadotrophins.
• Inhibiting hormones: inhibit pituitary secretion. Example: somatostatin from the hypothalamus inhibits release of growth hormone from the pituitary.
• These hormones come from hypothalamic neurons, pass through axons and are released from nerve endings.
• They reach the anterior pituitary through a portal circulatory system and regulate its functions.
• The posterior pituitary is under direct neural regulation of the hypothalamus.

Worked example

How does the hypothalamus control the anterior and posterior pituitary differently? Give one example of a releasing and one of an inhibiting hypothalamic hormone. (3 marks)

Try it first, then show the solutionSolution

1. Anterior pituitary: hypothalamic hormones reach it through a portal circulatory system (blood). (1)
2. Posterior pituitary: under direct neural control; axons of hypothalamic neurons extend into it. (1)
3. Releasing: GnRH (stimulates gonadotrophin release); inhibiting: somatostatin (inhibits growth hormone release). (1)

Answer: Portal blood to the anterior lobe, nerves to the posterior lobe; GnRH and somatostatin.

Pituitary and pineal glands

NCERT section 19.2.2 The Pituitary Gland; 19.2.3 The Pineal Gland

Pituitary gland:

• Located in a bony cavity called the sella turcica, attached to the hypothalamus by a stalk.
• Divided anatomically into the adenohypophysis and neurohypophysis.

Adenohypophysis (two portions):

• Pars distalis (often called the anterior pituitary) produces:
• Growth hormone (GH).
• Prolactin (PRL): growth of mammary glands and milk formation.
• Thyroid stimulating hormone (TSH): stimulates synthesis and secretion of thyroid hormones.
• Adrenocorticotrophic hormone (ACTH): stimulates synthesis and secretion of glucocorticoids from the adrenal cortex.
• Luteinising hormone (LH) and follicle stimulating hormone (FSH) (gonadotrophins): in males, LH stimulates synthesis and secretion of androgens from the testis; FSH, together with androgens, controls sperm formation (spermatogenesis). In females, LH triggers release of the ovum from a mature Graafian follicle (ovulation) and keeps the corpus luteum going; FSH stimulates growth and development of ovarian follicles.
• Pars intermedia secretes melanocyte stimulating hormone (MSH), which acts on melanocytes and regulates skin pigmentation. In humans, the pars intermedia is almost merged with the pars distalis.

Neurohypophysis (pars nervosa / posterior pituitary): stores and releases two hormones that are actually made by the hypothalamus and carried down axons:

• Oxytocin: acts on smooth muscles; stimulates vigorous contraction of the uterus at childbirth and milk ejection from the mammary gland.
• Vasopressin (ADH): acts mainly on the kidney, stimulating reabsorption of water and electrolytes by the distal tubules, reducing water loss in urine (diuresis).

GH disorders:

• Over-secretion of GH stimulates abnormal growth: gigantism.
• Low secretion stunts growth: pituitary dwarfism.
• Excess GH in adults, especially in middle age, causes acromegaly: severe disfigurement, especially of the face. It can lead to serious complications and premature death if unchecked; it is hard to diagnose early and often goes undetected for years.
• ADH deficiency: impaired water reabsorption, so water is lost and the person becomes dehydrated: diabetes insipidus.

Pineal gland:

• On the dorsal side of the forebrain.
• Secretes melatonin, which regulates the 24-hour (diurnal) rhythm of the body, e.g. sleep-wake cycle and body temperature.
• Melatonin also influences metabolism, pigmentation, the menstrual cycle and the body's defence capability.

Worked example

Distinguish between gigantism and acromegaly. Which hormone is involved, and which part of the pituitary secretes it? (3 marks)

Try it first, then show the solutionSolution

1. Both are due to excess growth hormone (GH), secreted by the pars distalis of the adenohypophysis. (1)
2. Gigantism: excess GH during childhood/growth, causing abnormal overall growth (very tall stature). (1)
3. Acromegaly: excess GH in adults, especially middle age, causing severe disfigurement, especially of the face. (1)

Answer: Both from excess GH (pars distalis); gigantism in the young, acromegaly in adults.

Thyroid and parathyroid glands

NCERT section 19.2.4 Thyroid Gland; 19.2.5 Parathyroid Gland

Thyroid gland:

• Two lobes on either side of the trachea, joined by a thin flap of connective tissue, the isthmus.
• Made of follicles and stromal tissue. Each follicle has follicular cells around a cavity.
• Follicular cells make tetraiodothyronine (T₄, thyroxine) and triiodothyronine (T₃).
• Iodine is essential for normal rate of thyroid hormone synthesis.

Functions of thyroid hormones:

• Regulate the basal metabolic rate (BMR).
• Support formation of red blood cells.
• Control metabolism of carbohydrates, proteins and fats.
• Maintain water and electrolyte balance.
• The thyroid also secretes a protein hormone, thyrocalcitonin (TCT), which regulates (lowers) blood calcium levels.

Disorders:

• Iodine deficiency → hypothyroidism and enlargement of the thyroid: goitre.
• Hypothyroidism during pregnancy causes defective development of the baby: cretinism: stunted growth, mental retardation, low IQ, abnormal skin, deaf-mutism, etc.
• In adult women, hypothyroidism may cause an irregular menstrual cycle.
• Hyperthyroidism (cancer of the thyroid or nodules) raises thyroid hormones to abnormal levels, affecting body physiology.
• Exophthalmic goitre (Graves' disease): a form of hyperthyroidism with enlarged thyroid, protruding eyeballs, increased BMR and weight loss.

Parathyroid glands:

• Four glands on the back side of the thyroid, one pair in each lobe.
• Secrete a peptide hormone, parathyroid hormone (PTH).
• PTH secretion is regulated by circulating calcium ion levels.
• PTH increases blood Ca²⁺: it is a hypercalcaemic hormone. It acts on bones (stimulating bone resorption/demineralisation), on the kidney tubules (Ca²⁺ reabsorption) and on absorption of Ca²⁺ from digested food.
• PTH and TCT together regulate body Ca²⁺ balance (PTH raises, TCT lowers).

Worked example

Name the two hormones that regulate blood calcium, their glands and their opposite effects. (3 marks)

Try it first, then show the solutionSolution

1. Parathyroid hormone (PTH) from the parathyroid glands raises blood Ca²⁺ (hypercalcaemic). (1)
2. Thyrocalcitonin (TCT) from the thyroid lowers blood Ca²⁺. (1)
3. PTH acts by bone resorption, Ca²⁺ reabsorption in kidney tubules and absorption from food; together PTH and TCT keep Ca²⁺ balanced. (1)

Answer: PTH (parathyroid) raises; TCT (thyroid) lowers.

Thymus and adrenal glands

NCERT section 19.2.6 Thymus; 19.2.7 Adrenal Gland

Thymus:

• A lobular structure between the lungs, behind the sternum on the ventral side of the aorta.
• Plays a major role in developing the immune system.
• Secretes peptide hormones, thymosins, which play a major role in differentiation of T-lymphocytes (cell-mediated immunity) and promote antibody production (humoral immunity).
• The thymus is degenerated in old individuals, so thymosin production falls; as a result, immune responses of old persons become weak.

Adrenal glands: one pair, at the anterior part of each kidney. Each has an outer adrenal cortex and an inner adrenal medulla.

Adrenal medulla: secretes adrenaline (epinephrine) and noradrenaline (norepinephrine), together called catecholamines.

• Secreted rapidly in stress or emergency: emergency hormones or hormones of fight or flight.
• Effects: alertness, dilation of pupils, piloerection (raising of hairs), sweating, increased heartbeat, strength of heart contraction and rate of respiration.
• Stimulate breakdown of glycogen (raising blood glucose), and breakdown of lipids and proteins.

Adrenal cortex: three layers: inner zona reticularis, middle zona fasciculata, outer zona glomerulosa. Secretes corticoids:

• Glucocorticoids (mainly cortisol): stimulate gluconeogenesis, lipolysis and proteolysis; inhibit cellular uptake and utilisation of amino acids. Also maintain the cardiovascular system and kidney functions, produce anti-inflammatory reactions and suppress the immune response, and stimulate RBC production.
• Mineralocorticoids (mainly aldosterone): act on renal tubules, stimulating reabsorption of Na⁺ and water and excretion of K⁺ and phosphate; so they keep salt levels, fluid volume, osmotic pressure and blood pressure steady.
• A little androgen (male-type steroid) is also made: help growth of axial, pubic and facial hair during puberty.

Addison's disease: the adrenal cortex makes too little hormone; carbohydrate metabolism is disturbed and the person suffers severe weakness and tiredness.

Worked example

Why are adrenaline and noradrenaline called emergency hormones? List four effects they produce. (3 marks)

Try it first, then show the solutionSolution

1. They are rapidly secreted by the adrenal medulla in response to stress or emergency (fight or flight). (1)
2. Effects: increased alertness, pupil dilation, piloerection, sweating (any two). (1)
3. Increased heart rate, strength of heart contraction and breathing rate; breakdown of glycogen raising blood glucose (any two). (1)

Answer: Released in stress; alertness, dilated pupils, faster heartbeat and breathing, more blood glucose.

Pancreas and gonads

NCERT section 19.2.8 Pancreas; 19.2.9 Testis; 19.2.10 Ovary

Pancreas: a composite gland, acting as both an exocrine (digestive enzymes) and endocrine gland.

• Endocrine part: Islets of Langerhans, about 1-2 million in a normal human pancreas, forming only 1-2% of pancreatic tissue.
• Main cells: α-cells secrete glucagon; β-cells secrete insulin.

Glucagon (peptide hormone):

• Maintains normal blood glucose.
• Acts mainly on liver cells (hepatocytes), stimulating glycogenolysis (glycogen → glucose), so blood sugar rises: hyperglycaemia.
• Stimulates gluconeogenesis.
• Reduces cellular glucose uptake and utilisation.
• So glucagon is a hyperglycaemic hormone.

Insulin (peptide hormone):

• Acts mainly on hepatocytes and adipocytes (fat cells), increasing cellular glucose uptake and utilisation, so glucose moves rapidly from blood into these cells: blood glucose falls (hypoglycaemia).
• Stimulates conversion of glucose to glycogen (glycogenesis) in target cells.
• Insulin and glucagon together keep blood glucose steady (glucose homeostasis).

Diabetes mellitus: prolonged hyperglycaemia causes this complex disorder, with loss of glucose through urine and formation of harmful ketone bodies. Patients are treated with insulin therapy.

Testis (in the scrotal sac, outside the abdomen):

• Has seminiferous tubules and stromal/interstitial tissue.
• Leydig (interstitial) cells in the inter-tubular spaces produce androgens, mainly testosterone.
• Androgens regulate the development, maturation and functions of male accessory sex organs (epididymis, vas deferens, seminal vesicles, prostate, urethra); bring about male features such as bigger muscles, beard and underarm hair, a deeper voice and aggressiveness; stimulate spermatogenesis; act on the CNS to influence male sexual behaviour (libido); and have anabolic (synthetic) effects on protein and carbohydrate metabolism.

Ovary (a pair in the abdomen):

• Produces one ovum in each menstrual cycle, and two groups of steroid hormones: estrogen and progesterone.
• Estrogen is made mainly by growing ovarian follicles. After ovulation, the ruptured follicle becomes the corpus luteum, which secretes mainly progesterone.
• Estrogen: growth and activities of female secondary sex organs, development of growing follicles, female secondary sex characters (e.g. high pitch of voice), mammary gland development, and female sexual behaviour.
• Progesterone: supports pregnancy; also acts on mammary glands, stimulating formation of alveoli (sac-like structures storing milk) and milk secretion.

Worked example

Explain how insulin and glucagon work together to keep blood glucose normal after a meal and during fasting. (3 marks)

Try it first, then show the solutionSolution

1. After a meal, blood glucose rises; β-cells release insulin, which increases glucose uptake by liver cells and fat cells and its conversion to glycogen, lowering blood glucose. (1½)
2. During fasting, blood glucose falls; α-cells release glucagon, which stimulates glycogenolysis and gluconeogenesis in the liver, raising blood glucose. (1)
3. Their opposite actions keep blood glucose within a normal range (glucose homeostasis). (½)

Answer: Insulin lowers glucose after meals; glucagon raises it during fasting.

Hormones of heart, kidney and gut; mechanism of hormone action

NCERT section 19.3 Hormones of Heart, Kidney and Gastrointestinal Tract; 19.4 Mechanism of Hormone Action

Hormones from non-endocrine tissues:

• Heart: the atrial wall secretes atrial natriuretic factor (ANF), which decreases blood pressure. When BP rises, ANF is secreted, causing dilation of blood vessels.
• Kidney: the juxtaglomerular cells produce erythropoietin, which stimulates erythropoiesis (RBC formation).
• Gastro-intestinal tract: endocrine cells secrete four major peptide hormones:
• Gastrin: acts on gastric glands, stimulating secretion of HCl and pepsinogen.
• Secretin: acts on the exocrine pancreas, stimulating secretion of water and bicarbonate ions.
• Cholecystokinin (CCK): acts on both pancreas and gall bladder, stimulating secretion of pancreatic enzymes and bile juice.
• Gastric inhibitory peptide (GIP): inhibits gastric secretion and motility.
• Several other non-endocrine tissues secrete growth factors essential for normal growth, repair and regeneration.

Mechanism of hormone action (elementary idea):

• Hormones produce effects by binding to specific proteins, hormone receptors, located only in target tissues.
• Receptors may be membrane-bound (on the cell membrane) or intracellular (nuclear receptors, inside the cell).
• Hormone + receptor = hormone-receptor complex, which causes certain biochemical changes in the target tissue, regulating metabolism and physiological functions.
• Each receptor is specific to one hormone.

Chemical types of hormones:

• Peptide, polypeptide, protein: insulin, glucagon, pituitary hormones, hypothalamic hormones.
• Steroids: cortisol, testosterone, estradiol, progesterone.
• Iodothyronines: thyroid hormones.
• Amino acid derivatives: epinephrine.

Two routes:

• Membrane-bound receptors: hormones that cannot enter the cell (mostly protein/peptide hormones) bind surface receptors and generate second messengers (e.g. cyclic AMP, IP₃, Ca²⁺), which regulate cellular metabolism.
• Intracellular receptors: steroid hormones and iodothyronines (thyroid hormones) enter the cell and bind receptors inside, mostly regulating gene expression or chromosome function, through interaction of the hormone-receptor complex with the genome. The resulting biochemical actions cause physiological and developmental effects.

Worked example

Why do insulin and cortisol use different routes to act on target cells? Name the second messenger idea. (3 marks)

Try it first, then show the solutionSolution

1. Insulin is a protein hormone that cannot cross the lipid membrane; it binds a membrane-bound receptor. (1)
2. The hormone-receptor complex generates second messengers (e.g. cAMP, IP₃, Ca²⁺) inside the cell, which regulate metabolism. (1)
3. Cortisol is a steroid; it crosses the membrane and binds an intracellular receptor, and the complex interacts with the genome to regulate gene expression. (1)

Answer: Protein hormones use surface receptors and second messengers; steroids act on intracellular receptors and genes.

Chemical Coordination and Integration in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Adrenal, Pancreas, Gonads and Hormone Action
• Pituitary, Thyroid and Parathyroid Hormones

Chemical Coordination and Integration: key facts

Hypothalamus-pituitary axis

$\text{hypothalamus}\stackrel{\text{releasing/inhibiting hormones (portal blood)}}{\to }\text{anterior pituitary}\stackrel{\text{TSH, ACTH, LH, FSH}}{\to }\text{target glands}$

Posterior pituitary releases oxytocin and ADH made in the hypothalamus.

Blood glucose control

$\text{insulin }(\beta \text{-cells})\Rightarrow \text{glucose}\downarrow ;\text{glucagon }(\alpha \text{-cells})\Rightarrow \text{glucose}\uparrow$

Hypoglycaemic vs hyperglycaemic hormones.

Blood calcium control

$\text{PTH (parathyroid)}\Rightarrow {\text{Ca}}^{2+}\uparrow ;\text{TCT (thyroid)}\Rightarrow {\text{Ca}}^{2+}\downarrow$

PTH is hypercalcaemic.

Adrenal cortex zones (inside to outside)

$\text{zona reticularis}\to \text{zona fasciculata}\to \text{zona glomerulosa}$

Corticoids: glucocorticoids, mineralocorticoids, small androgens.

Hormone action

$\text{hormone}+\text{receptor}\to \text{hormone-receptor complex}\to \text{second messenger or gene expression}\to \text{response}$

Protein hormones: membrane receptors; steroids and thyroid hormones: intracellular receptors.

Thyroid hormones

${\text{T}}_4=\text{tetraiodothyronine (thyroxine)};{\text{T}}_3=\text{triiodothyronine}$

Need iodine; regulate BMR.

Chemical Coordination and Integration: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

How the school exam asks Chemical Coordination and Integration

The question patterns to expect, and the method that works for each.

Tricks to remember Chemical Coordination and Integration

Short memory aids. Say each one aloud once, then use it on a question the same day.

• FLAT PeG

  Anterior pituitary hormones: FSH, LH, ACTH, TSH, PRL, GH.

  Use it when: Pars distalis hormones.

• Posterior stores, hypothalamus makes

  Oxytocin and vasopressin: made in hypothalamus, stored and released by neurohypophysis.

  Use it when: Origin of posterior pituitary hormones.

• GFR of the adrenal cortex

  From outside in: Glomerulosa, Fasciculata, Reticularis ('Go Find Rex'); salt (aldosterone), sugar (cortisol), sex (androgens).

  Use it when: Zones and their corticoids.

• Beta Brings it down

  β-cells make insulin (lowers glucose); α-cells make glucagon (raises it). 'Glucagon when Glucose is Gone'.

  Use it when: Pancreatic hormones.

• PTH Puts calcium in blood

  PTH raises blood calcium; Thyrocalcitonin Takes it down.

  Use it when: Calcium balance.

• Gastrin, Secretin, CCK, GIP: Go Slow, Calm, Go-stop

  Gastrin (acid), Secretin (bicarbonate), CCK (enzymes and bile), GIP (inhibits stomach).

  Use it when: Gut hormones.

Chemical Coordination and Integration: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section E style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 4-mark question split into 1 + 1 + 2 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Chemical Coordination and Integration

The slips examiners see most often, and what to write instead.

• ✗Mistake: Saying oxytocin and ADH are made in the posterior pituitary

  They are released there.

  ✓Do this: They are made by hypothalamic neurons and only stored and released by the neurohypophysis.

  Usually costs: 1 mark.

• ✗Mistake: Confusing goitre and exophthalmic goitre

  Both enlarge the thyroid.

  ✓Do this: Simple goitre: hypothyroidism (often iodine deficiency). Exophthalmic goitre (Graves'): hyperthyroidism with protruding eyes, high BMR and weight loss.

  Usually costs: 1 mark.

• ✗Mistake: Writing that glucagon lowers blood sugar

  The two pancreatic hormones are swapped.

  ✓Do this: Glucagon raises blood glucose (hyperglycaemic); insulin lowers it (hypoglycaemic).

  Usually costs: 1 mark.

• ✗Mistake: Calling acromegaly the adult form of dwarfism

  Both are GH disorders.

  ✓Do this: Acromegaly is excess GH in adults; dwarfism is low GH in childhood.

  Usually costs: 1 mark.

• ✗Mistake: Saying steroid hormones act through cAMP

  One mechanism applied to all hormones.

  ✓Do this: Steroids and thyroid hormones bind intracellular receptors and affect genes; protein hormones use membrane receptors and second messengers.

  Usually costs: 1 mark.

• ✗Mistake: Linking Addison's disease to the adrenal medulla

  Gland parts not separated.

  ✓Do this: Addison's disease is underproduction of hormones by the adrenal cortex.

  Usually costs: ½-1 mark.

NCERT exercise guide: Chemical Coordination and Integration

What each exercise in the NCERT chapter tests, how to approach it, and a question of the same kind solved step by step. Questions here are written in our own words.

Practice questions on Chemical Coordination and Integration

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQExam level

   Which gland secretes melatonin?
   (a) Pituitary (b) Pineal (c) Thyroid (d) Thymus

   Hint

   Dorsal forebrain.

   Answer

   (b) Pineal

2. Q2 · 1 mark · MCQExam level

   Exophthalmic goitre is caused by:
   (a) hyposecretion of thyroid hormones (b) hypersecretion of thyroid hormones (c) excess GH (d) deficiency of PTH

   Hint

   Graves' disease.

   Answer

   (b) hypersecretion of thyroid hormones

3. Q3 · 2 marks · Very short answerExam level

   Name the gland or tissue that (a) secretes thymosins, (b) contains the zona glomerulosa, (c) sits in the sella turcica, (d) contains Leydig cells. (2 marks)

   Hint

   Immunity; adrenal layers; bony cavity; testis.

   Answer

   (a) Thymus; (b) adrenal cortex (1). (c) Pituitary gland; (d) testis (1).

4. Q4 · 2 marks · Very short answerHarder exam level

   In iodine deficiency the output of T₃ and T₄ falls, yet the thyroid can go on making thyrocalcitonin. Explain why, and state what thyrocalcitonin does. (2 marks)

   Hint

   Which thyroid hormones are iodothyronines?

   Answer

   T₃ and T₄ are iodothyronines, and iodine is essential for their normal synthesis (1). Thyrocalcitonin is a protein hormone that contains no iodine, so its synthesis is not limited; it lowers (regulates) blood calcium levels (1).

5. Q5 · 2 marks · Very short answerHarder exam level

   What are the roles of LH and FSH in males and females? (2 marks)

   Hint

   Gonadotrophins.

   Answer

   Males: LH stimulates androgen secretion by the testis; FSH with androgens regulates spermatogenesis (1). Females: LH induces ovulation and maintains the corpus luteum; FSH stimulates growth of ovarian follicles (1).

6. Q6 · 2 marks · Very short answerHarder exam level

   Give the four chemical classes of hormones with one example each. (2 marks)

   Hint

   Peptide, steroid, iodothyronine, amino acid derivative.

   Answer

   Peptide/protein: insulin; steroid: cortisol (or testosterone); iodothyronine: thyroxine; amino acid derivative: epinephrine (½ each).

7. Q7 · 3 marks · Short answerHarder exam level

   In a boy, the Leydig cells of the testes fail to work at puberty. Which hormones would be lacking, and predict three effects on his development. (3 marks)

   Hint

   Interstitial cells; accessory organs, secondary characters, sperm.

   Answer

   Androgens, mainly testosterone, made by the Leydig (interstitial) cells would be lacking (1). The male accessory sex organs (epididymis, vas deferens, seminal vesicles, prostate, urethra) would not mature and function normally, and male secondary sex characters (muscular growth, facial and axillary hair, low-pitched voice) would not develop (1). Spermatogenesis would not be stimulated, male sexual behaviour (libido) would be reduced and the anabolic effects on protein and carbohydrate metabolism would be lost (1).

8. Q8 · 3 marks · Short answerHarder exam level

   During thyroid surgery a patient's parathyroid glands are accidentally removed, and a day later the patient develops rapid muscle spasms. Explain the link. (3 marks)

   Hint

   PTH is hypercalcaemic; low Ca²⁺ and muscles.

   Answer

   Without the parathyroids, no PTH is secreted; PTH normally raises blood Ca²⁺ by bone resorption, Ca²⁺ reabsorption in the kidney tubules and Ca²⁺ absorption from digested food (1½). So blood Ca²⁺ falls, and thyrocalcitonin from the remaining thyroid tissue is not opposed (½). Low Ca²⁺ in body fluids causes tetany, rapid spasms of the muscles (1).

9. Q9 · 5 marks · Long answerHarder exam level

   (a) A tumour cuts the stalk joining the hypothalamus to the pituitary. Predict the effect on (i) release of ADH and oxytocin and (ii) secretion of TSH and ACTH and the activity of their target glands. (b) Explain why a drug that blocks a hormone's receptors has much the same effect as removing the gland that makes the hormone. (5 marks)

   Hint

   Axons run down the stalk; so do portal vessels. Hormones act only through receptors.

   Answer

   (a)(i) ADH and oxytocin are made by hypothalamic neurons and carried down their axons to the neurohypophysis; with the stalk cut, their release falls, so water reabsorption drops and large volumes of dilute urine are passed (diabetes insipidus) (1½). (ii) Hypothalamic releasing hormones reach the anterior pituitary through the portal circulation in the stalk; without them TSH and ACTH secretion falls, so the thyroid and adrenal cortex are under-stimulated and secrete less (1½). (b) Hormones act only by binding specific receptors in target tissues to form a hormone-receptor complex, which then causes the biochemical changes (1). If the receptors are blocked no complex forms, so the target cells behave as if the hormone were absent (1).

10. Q10 · 3 marks · Short answerHOTS / competency

    Suppose a person's thyroid gland is surgically removed. Predict two changes in body functions and explain what hormone treatment would be required. (3 marks)

    Hint

    BMR and calcium.

    Answer

    No T₃/T₄ would be made, so BMR falls, causing tiredness, weight gain and sensitivity to cold; metabolism of carbohydrates, proteins and fats slows (1½). TCT would also be absent, affecting calcium regulation (PTH would still act) (½). Lifelong thyroid hormone (thyroxine) tablets would be needed to replace T₄ (1).

11. Q11 · 3 marks · Short answerHOTS / competency

    During a stressful exam, a student's blood glucose rises even though she has not eaten. Explain how two different hormones from the adrenal gland could cause this. (3 marks)

    Hint

    Medulla and cortex.

    Answer

    Stress triggers the adrenal medulla to release adrenaline/noradrenaline, which stimulate breakdown of glycogen, raising blood glucose quickly (1½). The adrenal cortex releases cortisol (a glucocorticoid), which stimulates gluconeogenesis and reduces amino acid uptake by cells, keeping glucose high over a longer time (1½).

12. Q12 · 1 mark · Assertion-reasonHOTS / competency

    Assertion (A): Insulin is called a hypoglycaemic hormone.
    Reason (R): Insulin stimulates glycogenolysis in liver cells.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

    Hint

    Which hormone breaks glycogen?

    Answer

    (c) A is true; R is false because insulin stimulates glycogenesis, while glucagon stimulates glycogenolysis.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Which hypothalamic hormone inhibits growth hormone release?Show answer

   Somatostatin.

2. 2.In which bony cavity does the pituitary sit?Show answer

   Sella turcica.

3. 3.Which pituitary hormone regulates skin pigmentation?Show answer

   MSH (melanocyte stimulating hormone) from the pars intermedia.

4. 4.Which hormone causes milk ejection?Show answer

   Oxytocin.

5. 5.What does melatonin regulate?Show answer

   The 24-hour diurnal rhythm, e.g. sleep-wake cycle and body temperature.

6. 6.What connects the two thyroid lobes?Show answer

   The isthmus.

7. 7.How many parathyroid glands are there?Show answer

   Four.

8. 8.Which hormones help T-lymphocytes differentiate?Show answer

   Thymosins.

9. 9.Name the main glucocorticoid and mineralocorticoid.Show answer

   Cortisol; aldosterone.

10. 10.How many islets of Langerhans are in a human pancreas?Show answer

    About 1-2 million (1-2% of pancreatic tissue).

11. 11.Which cells of the testis make testosterone?Show answer

    Leydig (interstitial) cells.

12. 12.Which kidney cells produce erythropoietin?Show answer

    Juxtaglomerular cells.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Can you define a hormone in the modern sense?
• ☐Can you name all pituitary hormones and their targets?
• ☐Can you explain the difference between gigantism, dwarfism and acromegaly?
• ☐Can you list five functions of thyroid hormones and the symptoms of cretinism?
• ☐Can you explain how PTH and TCT regulate blood calcium?
• ☐Can you name the three adrenal cortex zones and the three groups of corticoids?
• ☐Can you explain insulin and glucagon actions and diabetes mellitus?
• ☐Can you describe membrane and intracellular receptor mechanisms with examples?

Chemical Coordination and Integration: frequently asked questions