Chapter 15 — Movement, nerves and hormones

Structure makes movement possible

The human skeleton supports the body, helps protect organs and provides places for muscle attachment. The skull protects much of the brain; the rib cage surrounds the heart and lungs; the vertebral column helps support the trunk and protects the spinal cord. Bones are living tissues, not lifeless rods. At a joint, two or more skeletal elements meet. Different joints allow different ranges and directions of movement. A fixed skull suture, elbow hinge and shoulder ball-and-socket joint should not be assigned the same movement pattern simply because all are places where bones meet.

Skeletal muscles can pull on bones through tendons. Muscles contract; they do not actively push a bone away in the same way. Antagonistic muscles work in opposing directions across a joint: at the elbow, the biceps and triceps contribute to flexion and extension in the basic model. When the forearm bends, biceps contraction is prominent while the opposing muscle's state changes; when it straightens, the pattern reverses. The real movement involves coordination, joint geometry and other muscles, but the paired model is enough for common MCQs.

A tendon attaches muscle to bone. A ligament connects bone to bone and helps stabilise a joint. Cartilage can cover joint surfaces and reduce friction in suitable locations. A sprain involves ligament injury in the usual school distinction, whereas a strain involves muscle or tendon tissue. These names describe categories, not a diagnosis from one symptom. The book uses them only for factual classification. An exam item that gives a diagram should be solved by tracing what each band joins before memorising a label.

Skeletal muscle is usually voluntary; smooth muscle in many internal organs and cardiac muscle in the heart are generally involuntary. Involuntary does not mean independent of control: neural and chemical systems regulate them. Cardiac muscle is striated yet involuntary, so a rule “striped muscle = voluntary” is incomplete. The heart's contraction is muscular work, but its tissue is not identical to the skeletal muscle that bends an arm.

Signal pathways through nervous tissue

A neuron receives, integrates and transmits signals. Dendrites are receiving processes in a typical diagram; the axon carries an impulse away from the cell body toward other cells in the standard school representation. Signal direction through a neural circuit is a stronger guide than merely naming a long branch. A nerve is a bundle of axons and supporting tissue, not a single giant neuron. The central nervous system consists of brain and spinal cord; peripheral nerves connect it with receptors, muscles and organs.

At a synapse, one neuron's signal can influence another cell through specialised communication. In many chemical synapses, neurotransmitter released from one side binds receptors on the next cell. An electrical impulse does not simply jump an empty gap as a wire spark in every case. Neurons communicate rapidly compared with many endocrine signals, though exact speeds vary widely. “Nervous control is always instantaneous and hormonal control is always slow” is too absolute. At exam level, compare typical route and mechanism: neural pathways versus hormones carried in body fluids.

A reflex is a rapid, relatively automatic response to a stimulus through a defined circuit. A basic reflex arc includes receptor → sensory neuron → central processing region → motor neuron → effector. In many familiar spinal reflexes, the response can begin through spinal circuitry before conscious awareness, while the brain still receives information and can influence behaviour. “The brain has no role in any reflex” is incorrect. The fact that a hand withdraws quickly from a harmful stimulus does not mean pain never reaches the brain.

The brain has regions with different important functions. The cerebrum supports many conscious perceptions, voluntary actions and higher processes; the cerebellum helps coordinate movement and balance; the brainstem contains centres important for basic functions. These are broad role maps, not a claim that each function resides exclusively in one isolated compartment. A match question may ask for the region most associated with balance, and cerebellum is a standard answer. But complex behaviour depends on networks across the nervous system.

The eye and ear are sensory organs that convert physical stimuli into neural signals. Light stimulates retinal cells; sound waves set up mechanical vibrations that ultimately stimulate sensory cells in the inner ear. The optic nerve carries visual information to the brain; hearing also requires neural processing. A lens or eardrum alone does not “see” or “hear.” In a diagram question, identify where stimulus transduction occurs and where the signal travels. This connects physics chapters on light and sound to biology without merging their distinct mechanisms.

Hormones as chemical messages

Endocrine glands release hormones into blood or other body fluids rather than through an external duct. The pancreas has endocrine cells that produce insulin and glucagon, which participate in regulation of blood glucose. It also has exocrine digestive function through ducts. A question describing pancreatic enzymes in the intestine and one describing insulin in blood refer to different functions of the same organ. This dual role explains why “the pancreas is only a digestive gland” is not an adequate answer.

The thyroid gland produces hormones involved in metabolism and development; iodine is needed to make thyroid hormones. Iodine deficiency can contribute to goitre in relevant settings, but a visible enlarged thyroid has multiple possible causes. This book does not ask a candidate to diagnose a person from a photograph. The adrenal glands produce hormones with roles in stress responses and other regulation; the pituitary has major coordinating endocrine roles. “Master gland” can be a convenient school phrase for pituitary, but the hypothalamus and feedback loops influence its activity, so it is not completely independent.

Feedback helps keep internal conditions within a useful range. In a simple negative-feedback illustration, a measured variable changing in one direction triggers responses that tend to oppose the change. Blood glucose regulation is more complex than a single switch, but insulin can help lower elevated blood glucose by promoting uptake and storage in appropriate contexts, while glucagon can help raise low blood glucose by mobilising stores. Do not infer that “more insulin is always better” from this direction; the body requires regulation, and clinical decisions are outside this exam guide.

Puberty involves changes controlled in part by hormones from the brain and gonads. Hormones influence reproductive maturation, but physical changes vary among individuals and are not a clock that proves an exact age. For an MCQ, know that testes produce testosterone and ovaries produce oestrogens and progesterone in the broad school account, while their regulation involves pituitary signals. Avoid reducing a complex developmental process to one hormone acting alone.

Compare signal and response

Suppose a hand touches a hot surface. Receptors detect a stimulus, a sensory pathway carries information, a spinal circuit can initiate muscle withdrawal, and the brain processes the experience. If an option says “the hand moves only after the brain completes a conscious decision,” it misses the purpose of the rapid reflex. If another says “the spinal cord permanently prevents the brain from knowing,” it is also wrong. The causal sequence, not an isolated organ name, resolves the item.

Suppose a different question asks how one endocrine gland can influence a distant tissue. The gland releases a hormone into the circulation; only cells with appropriate receptors respond in the relevant way. “Every cell touched by blood responds equally” is false. Compare this with a neuron circuit, whose connections determine the route. Both systems coordinate the organism and interact, but their carrier and target mechanisms differ.

Worked joint route

A sketch shows a round head of bone fitting into a cup-shaped socket, with movement possible in several directions. The expected school classification is ball-and-socket, as at the shoulder or hip. A second sketch allows mainly bending and straightening in one plane: hinge, as at the elbow. Classify by permitted movement and geometry, not by whether both joints are in an arm. If a question asks what holds bones together at the joint, choose ligament rather than tendon.

For a gland-matching item, place pancreas with insulin and glucagon, thyroid with thyroid hormones, and adrenal with adrenal hormones. A stem may pair insulin with “digestive secretion through a duct”; that mismatches route even though pancreas also sends enzymes through ducts. Reading the word hormone is essential. If a question concerns disease diagnosis, current medical knowledge is needed; this chapter limits itself to basic structure and regulation for exam recall.

Bone and joint questions: separate material from connection

Bone contains living cells within a matrix that includes collagen and mineral components. The combination provides properties different from either a flexible fibre alone or a brittle mineral alone. Bone marrow has important functions, including blood-cell formation in red marrow. This helps explain why the skeleton is more than a support frame. Cartilage is a different connective tissue, found at several sites including joint surfaces and parts of the ear and respiratory passages. It is not simply an immature bone in every location. A question about a tissue's location must be distinguished from a question about whether it can be replaced during development.

A joint's range of movement depends on its shape, connecting tissues and surrounding muscles. The shoulder permits movement in several directions, while the elbow's principal bending action illustrates a hinge. A pivot arrangement permits rotation around an axis, as in the familiar upper-neck comparison. Gliding movements occur between relatively flat surfaces in suitable joints. The usual textbook count of 206 bones refers to a typical adult skeleton; it is not an unchanging count for every developmental stage or anatomical variation. For a straightforward exam item, identify whether it specifically asks about the adult human skeleton.

Muscle force and movement can be linked to the lever principles studied in Physics. The joint acts as a pivot, muscle force acts at an attachment, and an external load acts through its own moment arm. If a simplified forearm problem gives a load of 20 N at 0.30 m from the elbow and a muscle's perpendicular moment arm of 0.04 m, balance requires muscle force × 0.04 = 20 × 0.30. The calculated force is 150 N, ignoring forearm weight and other forces. The muscle force exceeds the external load because it acts through a much shorter moment arm. This is a mechanics model, not a measure of any particular person's strength.

Contraction is coordinated rather than an on–off label

In the sliding-filament account, actin and myosin interact so that muscle's contractile units shorten as filaments slide relative to one another. The filaments do not have to shrink into smaller molecules for this shortening to occur. ATP is needed in the contractile cycle and in processes that restore the resting conditions. A muscle therefore uses energy even when it holds a load without visibly moving it. Mechanical work on a stationary external object is zero in the elementary Physics definition, but metabolism inside the muscle can continue. Distinguish the system whose work is being calculated.

Antagonistic action does not require one muscle to be completely inactive whenever its partner contracts. Posture and controlled movement may involve simultaneous activity that stabilises a joint. In introductory elbow questions, however, flexion is associated with the flexor action and extension with the extensor action. Use the simple paired model where it is asked, while avoiding the claim that real movements consist of only two perfectly isolated muscles. Tendons transmit force from muscle to bone; ligaments help stabilise bone-to-bone relationships. Neither structure produces contraction in the same way as muscle tissue.

Follow information through a circuit

A receptor detects a relevant stimulus, such as pressure, temperature change or light. A sensory pathway carries information towards the central nervous system; a motor pathway carries instructions towards an effector. An effector can be a muscle or a gland. These terms describe direction and role. A sensory neuron does not become a motor neuron simply because its signal travels quickly. “Afferent” is commonly used for a pathway towards a reference centre, and “efferent” for one away from it; in elementary nervous-system questions, the reference is the central nervous system.

Myelin surrounds many axons and helps rapid signal conduction by insulating sections of the axon. Gaps between myelinated segments are nodes of Ranvier. In a simplified account, the electrical signal is regenerated at these gaps, allowing saltatory conduction. Not every axon is myelinated, and conduction speed also depends on features such as axon diameter. A question asking whether a nerve impulse is merely blood carrying a chemical from the brain should be rejected: electrical activity along neurons and chemical transmission at many synapses form a different communication route from endocrine circulation.

At a typical chemical synapse, an arriving signal promotes neurotransmitter release from a presynaptic terminal. The transmitter diffuses across a very small gap and interacts with receptors on the receiving cell. The response can increase or decrease the likelihood of further activity, depending on the transmitter, receptor and circuit. Thus a synapse is not merely an unquestioning relay that forces the next neuron to fire every time. At school level, the key contrast is electrical propagation along a neuron and chemical communication across many synapses, with the recognition that electrical synapses also exist.

Reflex and reaction-time evidence

A familiar withdrawal reflex can use a spinal circuit to begin a protective movement before a complete conscious decision. The route still includes sensory input, central processing and motor output; it is not a response without nervous-system involvement. Some reflexes involve the brainstem, and higher centres can influence many reflex pathways. “All reflexes use only the spinal cord” is therefore too broad. A knee-jerk example has a simpler core connection than a withdrawal response, so do not assume that every reflex arc must contain the same number of relay neurons.

A ruler-drop activity can estimate a response time under carefully defined conditions. If a ruler falls from rest through distance d and air resistance is ignored, d = gt²/2, so t = square root of 2d/g. A catch after a fall of 0.20 m gives t approximately 0.20 s using g approximately 10 m/s². The result includes sensory processing and the movement needed to catch the ruler; it is not the speed of a single nerve impulse. Repeating trials and using a consistent method reduces the influence of chance anticipation and inconsistent release.

Suppose one trial is faster after practice. The result alone does not prove that the person's axons became physically longer or that a new hormone caused the change. Attention, anticipation, technique and measurement error can affect performance. A comparison should use several trials, the same starting arrangement and an appropriate summary. This is a general exam skill: identify what the experiment measures directly before choosing a biological explanation. Do not convert a small classroom observation into a claim about a person's health or intelligence.

Sensory organs: match the physical event to its location

In vision, the cornea and lens help focus light onto the retina. The iris controls pupil size and thereby affects the light admitted. The retina contains photoreceptors; rods are especially important in dim-light sensitivity and cones in colour vision and detailed daylight vision. The optic nerve carries information towards the brain. The pupil is an opening rather than a focusing lens. A question that identifies it as the structure that chemically detects light mixes up light entry with sensory conversion. Accommodation involves changes in lens shape through the action of the ciliary apparatus.

In hearing, the external ear collects sound, the eardrum vibrates, and middle-ear bones transmit vibration towards the inner ear. The cochlea contains structures that convert mechanical vibration into neural information. The semicircular canals are more closely associated with sensing head rotation and balance than with detecting sound frequency. This is a frequent organ-part confusion because both belong to the inner ear. The auditory tube helps equalise pressure across the eardrum; it is not the nerve that carries sound information to the brain.

Physics and Biology provide complementary descriptions. Sound frequency helps determine pitch, while sensory structures and neural pathways make hearing possible. A convex lens can focus light, but a lens by itself does not interpret an image. In an examination, decide whether the stem concerns physical focusing, receptor stimulation or neural interpretation. This prevents a correct Physics fact from being attached to the wrong anatomical structure.

Hormone pathways and feedback loops

Endocrine signalling can be organised as stimulus, gland, hormone, target response and feedback. In a simplified thyroid pathway, hypothalamic signals influence the pituitary, pituitary thyroid-stimulating hormone influences the thyroid, and thyroid hormones affect tissues and feed back on the controlling centres. The pituitary is therefore part of a regulated network. An enlarged gland or a changed hormone concentration cannot be explained from one arrow alone without context; for exam purposes, learn the direction and the named hormone–gland association.

Negative feedback opposes a departure from a regulated condition. Positive feedback reinforces a process in a particular setting until a terminating event occurs; it is not automatically a harmful or unsuccessful mechanism. Childbirth-related oxytocin signalling is a familiar teaching example of positive feedback, whereas many endocrine control loops use negative feedback. The labels describe the direction of the loop's effect, not whether the hormone is “good” or “bad.” A thermostat is an analogy for negative feedback, but a living regulatory system can have multiple sensors, targets and interacting controls.

Antidiuretic hormone, also called vasopressin, provides a useful link to kidney function. It is synthesised in the hypothalamus and released into the circulation from the posterior pituitary. It can increase water reabsorption in the kidneys through actions on appropriate target structures. A question about synthesis and one about release may therefore have different anatomical answers. This is another reason to read the verb in a gland-matching item. Growth hormone is associated with the anterior pituitary, while adrenaline is associated with the adrenal medulla in the standard introductory map.

Retrieval practice with reasons

Case A: A band joins a skeletal muscle to bone. It is a tendon; a ligament would join bones in the elementary distinction. Case B: A sensory message travels towards the spinal cord. This is an afferent direction relative to the central nervous system. Case C: The inner-ear structure named in a question is the cochlea. Associate it with hearing, while semicircular canals help detect head rotation.

Case D: A simplified lever has a 10 N load at 0.24 m and a muscle moment arm of 0.03 m. Required balancing muscle force is 80 N, subject to the stated simplifications. Case E: A gland releases its product through a duct onto an epithelial surface. That route is exocrine, not endocrine. Case F: A hormone is synthesised in the hypothalamus and released from the posterior pituitary. Vasopressin fits this route; answering only “pituitary makes every hormone it releases” would miss the distinction.

Recall and review

Compare hinge, ball-and-socket and fixed joints by movement. Distinguish tendon from ligament and skeletal from cardiac muscle. Trace a reflex arc in order and state why the brain can still receive information. Match cerebellum to coordination without making it the sole controller of movement. Explain the difference between neural signalling and endocrine release, then describe a simple negative-feedback loop. Attempt the chapter practice set, then use the explanations to revisit any uncertain concepts.

Figure 15. Original chapter diagram.

Practice 31 questions

Choose one answer for each item. The answer key and explanations follow this chapter set.

1. Which hormone prepares the body for "fight or flight" by raising the heart rate and blood pressure during sudden stress?

A. Insulin B. Adrenaline C. Thyroxine D. Melatonin

2. Which photoreceptor cells of the retina detect colour and work best in bright light?

A. Rods B. Cones C. Sensory neurons D. Glial cells

3. How many cervical vertebrae are present in the neck of a normal adult human being?

A. 5 B. 7 C. 9 D. 12

4. Assertion (A): Central diabetes insipidus can cause large volumes of dilute urine without high blood glucose. Reason (R): In central diabetes insipidus the body produces too little vasopressin (ADH), reducing kidney water reabsorption. Choose the correct option.

A. Both A and R are true and R explains A B. Both A and R are true but R does not explain A C. A is true but R is false D. A is false but R is true

5. Match List-I (Hormone) with List-II (Main function):
List-I: (a) Prolactin (b) ADH (c) Insulin (d) Cortisol
List-II: (i) Lowers blood glucose (ii) Increases water reabsorption in kidney tubules (iii) Manages the response to long-term stress (iv) Stimulates milk production

A. a-ii, b-iv, c-i, d-iii B. a-iv, b-ii, c-iii, d-i C. a-iv, b-i, c-ii, d-iii D. a-iv, b-ii, c-i, d-iii

6. Match the thyroid-related condition with its description. List I: (a) untreated congenital hypothyroidism; (b) severe adult hypothyroidism with myxoedema; (c) Graves’ disease; (d) iodine-deficiency goitre. List II: (i) autoimmune thyroid overactivity; (ii) enlarged thyroid related to iodine deficiency; (iii) thyroid hormone deficiency from birth that can impair development if untreated; (iv) severe adult thyroid deficiency with tissue puffiness.

A. a-iv, b-iii, c-i, d-ii B. a-iii, b-iv, c-i, d-ii C. a-iii, b-iv, c-ii, d-i D. a-i, b-iv, c-iii, d-ii

7. Which statement best describes a common mechanism in type 2 diabetes mellitus?

A. The pancreas makes no insulin at all, and the disease usually starts in childhood B. It is caused by a deficiency of ADH from the pituitary gland C. Body cells stop responding properly to insulin even though the pancreas still makes it D. It is caused by an excess of glucagon from the thyroid gland

8. Adrenocorticotropic hormone (ACTH) of the pituitary gland stimulates which of the following?

A. Adrenal cortex B. Adrenal medulla C. Thyroid gland D. Ovaries and testes

9. Calcitonin, a hormone that lowers the calcium level in blood, is secreted by the:

A. Thyroid gland B. Parathyroid glands C. Adrenal cortex D. Pituitary gland

10. Excess secretion of growth hormone during childhood, before the growth plates of bones close, causes:

A. Acromegaly B. Dwarfism C. Gigantism D. Cretinism

11. Glucagon, which raises blood glucose, is secreted by which cells of the islets of Langerhans?

A. Beta cells B. Alpha cells C. Delta cells D. Acinar cells

12. Melatonin, the hormone that regulates the sleep-wake cycle, is secreted by which gland?

A. Pituitary gland B. Thymus C. Pineal gland D. Thyroid gland

13. Myxoedema, marked by puffiness, dry skin, weight gain and mental slowness in adults, is caused by deficiency of which hormone?

A. Insulin B. Growth hormone C. Cortisol D. Thyroxine

14. Which hormone of the adrenal cortex regulates sodium and water balance by controlling how much sodium the kidneys retain?

A. Aldosterone B. Adrenaline C. Glucagon D. Melatonin

15. Oxytocin and ADH (antidiuretic hormone) are made in the hypothalamus but are stored and released into the blood from which part of the endocrine system?

A. Pineal gland B. Thyroid gland C. Posterior pituitary D. Anterior pituitary

16. Parathormone (PTH), secreted by the parathyroid glands, has which effect on the body?

A. It lowers the glucose level in blood B. It raises the calcium level in blood C. It lowers the calcium level in blood D. It raises the basal metabolic rate

17. Consider the following statements:
Statement I: Calcitonin, secreted by the thyroid gland, lowers the level of calcium in the blood.
Statement II: Parathormone, secreted by the thyroid gland, raises the level of calcium in the blood.
Which of the above is/are correct?

A. Only I B. Only II C. Both I and II D. Neither I nor II

18. Consider the statements. I: Central diabetes insipidus can result from too little vasopressin (ADH). II: Diabetes mellitus causes excessive dilute urination without affecting blood glucose. Which statement(s) is/are correct?

A. Only I B. Only II C. Both I and II D. Neither I nor II

19. Consider the following statements:
Statement I: Excess growth hormone before the growth plates of the long bones close causes gigantism.
Statement II: Excess growth hormone in an adult makes the person grow much taller, a condition called acromegaly.
Which of the above is/are correct?

A. Only I B. Only II C. Both I and II D. Neither I nor II

20. Consider the statements. I: Sensory hair cells in the cochlea help convert sound movement into electrical signals. II: Semicircular canals contribute to sensing head rotation and balance. Which statement(s) is/are correct?

A. Only I B. Only II C. Both I and II D. Neither I nor II

21. Which of the following hormones is NOT produced by the anterior pituitary?

A. Growth hormone B. Thyroid-stimulating hormone C. Oxytocin D. Prolactin

22. Which of the following is NOT an endocrine (ductless) gland?

A. Thyroid gland B. Adrenal gland C. Pituitary gland D. Salivary gland

23. Which coloured part of the eye changes the pupil opening to regulate the amount of light entering?

A. Iris B. Retina C. Optic nerve D. Cornea

24. Arrange the following in the order in which sound vibrations pass through them in the human ear:
(A) Stapes (B) Malleus (C) Incus (D) Tympanic membrane (E) Cochlea

A. D, B, C, A, E B. D, C, B, A, E C. B, D, C, A, E D. D, A, C, B, E

25. Match List-I (Eye disorder) with List-II (Correction):
List-I: (a) Myopia (b) Hypermetropia (c) Astigmatism (d) Cataract
List-II: (i) Cylindrical lens (ii) Surgical replacement of the lens (iii) Convex lens (iv) Concave lens

A. a-iii, b-iv, c-i, d-ii B. a-iv, b-iii, c-ii, d-i C. a-i, b-iii, c-iv, d-ii D. a-iv, b-iii, c-i, d-ii

26. Presbyopia commonly makes near objects harder to focus on with age mainly because:

A. The retina becomes a convex lens B. The eye’s lens becomes less flexible and accommodates less C. The iris stops detecting colours D. The optic nerve changes the shape of the cornea

27. The knee-jerk response tested by a doctor is a simple reflex action controlled mainly by the:

A. Cerebrum B. Cerebellum C. Hypothalamus D. Spinal cord

28. Which is the largest part of the human brain, the seat of memory, reasoning and voluntary actions?

A. Cerebellum B. Cerebrum C. Medulla oblongata D. Pons

29. Which part of a neuron carries the nerve impulse away from the cell body towards another neuron, muscle or gland?

A. Dendrite B. Axon C. Cyton D. Myelin sheath

30. Which part of the brain regulates body temperature, hunger and thirst, and links the nervous system with the pituitary gland?

A. Hypothalamus B. Thalamus C. Cerebellum D. Pons

31. Which part of the inner ear converts sound vibrations into nerve impulses sent to the brain through the auditory nerve?

A. Semicircular canals B. Eustachian tube C. Tympanic membrane D. Cochlea

Answers and explanations

1. B. Adrenaline (epinephrine), released by the adrenal medulla within seconds of a threat, raises heart rate and blood pressure and diverts blood to muscles. Insulin lowers blood sugar, thyroxine sets metabolic rate and melatonin regulates sleep.

2. B. Cones detect colour and work best in bright light, while rods detect dim light and shades of grey and are useful at night. A handy hook is "Cones for Colour"; colour blindness is a fault of certain cone cells.

3. B. A human being has 7 cervical vertebrae; the full column has 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused) and 4 coccygeal (fused) vertebrae. The number 12 is the thoracic count and 5 is the lumbar count.

4. A. Both are true and R explains A. In central diabetes insipidus, deficient vasopressin signalling causes the kidneys to conserve less water, producing much dilute urine. Other types of diabetes insipidus exist: in nephrogenic disease the kidneys fail to respond adequately even when hormone is present. The condition differs from diabetes mellitus.

5. D. Prolactin stimulates milk production (a-iv), ADH increases water reabsorption in kidney tubules (b-ii), insulin lowers blood glucose (c-i), and cortisol from the adrenal cortex manages long-term stress and metabolism (d-iii).

6. B. Untreated congenital hypothyroidism matches iii; severe adult hypothyroidism with myxoedema matches iv; Graves’ disease is autoimmune hyperthyroidism (i); iodine-deficiency goitre matches ii. The code is a-iii, b-iv, c-i, d-ii. The older label “cretinism” is avoided, and goitre is not presented as always caused by iodine deficiency.

7. C. Insulin resistance means body cells respond less effectively to insulin, a common feature of type 2 diabetes. The pancreas may still make insulin, although insulin secretion can also decline over time. Type 1 diabetes involves autoimmune beta-cell loss and can begin at different ages. Vasopressin-related diabetes insipidus is a different disorder.

8. A. ACTH acts on the adrenal cortex to release cortisol. The adrenal medulla is controlled by sympathetic nerves rather than ACTH, the thyroid is stimulated by TSH, and the gonads by FSH and LH.

9. A. Calcitonin is secreted by thyroid C cells and can lower blood calcium, partly by inhibiting bone resorption. In humans, parathyroid hormone and vitamin D are major regulators of calcium balance, so the effect should not be reduced to simply “moving calcium into bone”. The correct gland is thyroid, not parathyroid.

10. C. Excess growth hormone before the long-bone growth plates close can cause gigantism. After plate closure, excess causes acromegaly instead. Growth-hormone deficiency is one possible cause of short stature; “dwarfism” is not a single diagnosis. Congenital thyroid deficiency is a different condition.

11. B. Alpha cells of the islets secrete glucagon, which makes the liver break glycogen into glucose. Beta cells secrete insulin, delta cells secrete somatostatin, and acinar cells form the exocrine part that makes digestive enzymes.

12. C. The pineal gland produces melatonin, which helps coordinate circadian timing and is commonly higher in darkness. Light exposure can suppress it, depending on timing, intensity and wavelength. The other listed glands have different principal hormones.

13. D. Severe adult hypothyroidism can produce features historically called myxoedema. Reduced thyroid-hormone activity, not deficiency of insulin, growth hormone or cortisol, explains this exam association. Congenital hypothyroidism is the corresponding modern term for thyroid deficiency present from birth; the older label for affected children is avoided.

14. A. Aldosterone, a mineralocorticoid from the adrenal cortex, makes the kidneys retain sodium (and water), thereby affecting blood pressure. Adrenaline is from the adrenal medulla, glucagon from pancreatic alpha cells and melatonin from the pineal gland.

15. C. The posterior pituitary does not manufacture hormones; it stores and releases oxytocin and ADH, which are made in the hypothalamus and travel down a short nerve tract. The anterior pituitary makes GH, TSH, ACTH, FSH, LH and prolactin itself.

16. B. Parathyroid hormone raises blood calcium through effects on bone and kidney and indirectly on intestinal absorption via active vitamin D. Insulin chiefly affects blood glucose, while thyroxine affects metabolic rate. Calcitonin can lower blood calcium but is produced by thyroid C cells.

17. A. Only Statement I is correct. Calcitonin from the thyroid lowers blood calcium. Parathormone does raise blood calcium, but it is secreted by the four small parathyroid glands behind the thyroid, not by the thyroid.

18. A. Only I is correct. Central diabetes insipidus can reflect insufficient vasopressin production; nephrogenic diabetes insipidus instead involves kidney resistance to the hormone. Diabetes mellitus involves abnormal blood-glucose regulation, so Statement II is false.

19. A. Only Statement I is correct. After the growth plates close, extra growth hormone cannot make a person taller; in acromegaly the bones of the hands, feet and face thicken and enlarge instead.

20. C. Both are correct. Cochlear hair cells transduce mechanical sound vibrations into neural signalling, while the semicircular canals of the vestibular system detect angular head motion. These neighbouring inner-ear systems have related hair-cell mechanisms but different principal functions.

21. C. Oxytocin (like ADH) is made in the hypothalamus and only stored and released by the posterior pituitary. The anterior pituitary itself produces GH, TSH, ACTH, FSH, LH and prolactin.

22. D. Salivary glands are exocrine glands that pour saliva into the mouth through ducts. The thyroid, adrenal and pituitary glands are ductless endocrine glands that release hormones directly into the blood.

23. A. The iris contains muscles that change pupil diameter and therefore the amount of light entering the eye. The retina detects light, the optic nerve carries visual signals and the cornea is the clear front optical surface.

24. A. Sound makes the eardrum (tympanic membrane) vibrate; the vibrations pass through the ossicles malleus (hammer), incus (anvil) and stapes (stirrup), which amplify them, and then reach the cochlea. Order: D, B, C, A, E.

25. D. Myopia needs a concave lens (a-iv), hypermetropia a convex lens (b-iii), astigmatism a cylindrical lens (c-i), and cataract, a clouding of the natural lens, is treated by surgically replacing the lens (d-ii).

26. B. With age the crystalline lens becomes stiffer and less able to change shape for near focus, producing presbyopia. This is distinct from astigmatism, which arises from uneven optical curvature and was already tested in the preceding match question.

27. D. The patellar (knee-jerk) reflex is integrated chiefly through the spinal cord, allowing a rapid motor response after stretch receptors are stimulated. Information can still reach the brain, so “the brain is bypassed” should not be taken to mean the brain never receives or influences reflex-related activity.

28. B. The cerebrum, divided into two hemispheres with a folded cortex, is the largest part of the brain and controls thinking, memory, language and voluntary movement. The cerebellum fine-tunes movement and the medulla controls vital involuntary functions.

29. B. The axon is a long single fibre that conducts impulses away from the cell body. Dendrites are short branches that bring signals to the cell body (cyton), and the myelin sheath is only an insulating covering on many axons.

30. A. The hypothalamus regulates body temperature, hunger, thirst and other drives, and controls the pituitary through releasing hormones. The thalamus relays sensory signals to the cerebrum, and the cerebellum coordinates movement and balance.

31. D. The snail-shaped, fluid-filled cochlea converts vibrations into nerve signals and is the actual organ of hearing. Semicircular canals handle balance, the Eustachian tube equalises middle-ear pressure, and the eardrum only vibrates.