Exercise, temperature regulation and environmental physiology

10 NEET-PG practice questions on Exercise, temperature regulation and environmental physiology, part of Physiology. The first 10 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Medium

   A term newborn in a district hospital labour room is left uncovered on a cold table, and her axillary temperature falls to 35.6 °C. She does not shiver. What is her main source of extra heat?

   1. ABrown adipose tissue
   2. BSkeletal muscle shivering
   3. CWhite adipose tissue
   4. DHepatic glycogen breakdown

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   Answer: A · Brown adipose tissue

   Newborns rely on non-shivering thermogenesis in brown adipose tissue, found between the scapulae, around the neck and kidneys and along the great vessels. Noradrenaline from sympathetic nerves acts on beta-3 receptors, and uncoupling protein 1 (thermogenin) lets protons re-enter the mitochondrial matrix without making ATP, releasing the energy as heat. Preterm babies have little brown fat, so the warm chain, early drying and skin-to-skin (kangaroo) care prevent hypothermia.

   • B: Newborns shiver poorly; shivering is not their main heat source.
   • C: White fat stores energy; it lacks thermogenin and many mitochondria.
   • D: Glycogen breakdown supplies fuel but is not the specialised heat-producing mechanism.

2. Question 2 · Easy

   A 5-year-old girl seen at a PHC has a temperature of 39.2 °C with a viral cold; she shivered and felt cold before the fever rose. A dose of paracetamol brings her temperature down. How does paracetamol lower her temperature?

   1. AStimulates sweating via muscarinic receptors
   2. BDirectly dilates blood vessels in the skin
   3. CBlocks IL-1 release from macrophages
   4. DInhibits PGE2 synthesis in the hypothalamus

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   Answer: D · Inhibits PGE2 synthesis in the hypothalamus

   Pyrogenic cytokines such as IL-1, IL-6 and TNF-alpha induce COX-2 in the hypothalamic region, and the PGE2 formed raises the thermoregulatory set point. Until body temperature reaches the new set point the child feels cold and shivers. Paracetamol inhibits COX in the brain, PGE2 falls and the set point returns towards normal, so the body loses heat by vasodilation and sweating.

   • A: Paracetamol has no muscarinic action; sweating follows the reset.
   • B: Skin vasodilation follows the lowered set point; it is not a direct drug effect.
   • C: Paracetamol does not stop cytokine release from immune cells.

3. Question 3 · Hard

   During a cardiopulmonary exercise test, a 30-year-old man has an oxygen consumption of 2,400 mL/min. His arterial oxygen content is 20 mL/dL and mixed venous oxygen content 8 mL/dL. What is his cardiac output?

   1. A12 L/min
   2. B8.6 L/min
   3. C30 L/min
   4. D20 L/min

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   Answer: D · 20 L/min

   By the Fick principle, cardiac output = oxygen consumption / arteriovenous O2 difference. The difference is 20 - 8 = 12 mL/dL, or 120 mL/L. So cardiac output = 2,400 / 120 = 20 L/min, about four times a typical resting value, achieved by raising heart rate and stroke volume. The widened arteriovenous difference shows that working muscle extracts more oxygen.

   • A: 12 L/min uses the arterial content alone (2,400/200).
   • B: 8.6 L/min adds the two contents instead of subtracting (2,400/280).
   • C: 30 L/min uses the venous content alone (2,400/80).

4. Question 4 · Medium

   A healthy 25-year-old man runs on a treadmill at a moderately heavy pace during an exercise physiology practical. Compared with rest, which pattern of change is expected?

   1. ASBP rises, DBP changes little, TPR falls
   2. BSBP rises, DBP rises, TPR rises
   3. CSBP falls, DBP falls, TPR falls
   4. DSBP changes little, DBP rises, TPR rises

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   Answer: A · SBP rises, DBP changes little, TPR falls

   In dynamic exercise, sympathetic drive and venous return raise heart rate and stroke volume, so cardiac output and systolic pressure rise. At the same time metabolites dilate the large vascular bed of the working muscles, so total peripheral resistance falls and diastolic pressure changes little or falls slightly. Isometric exercise such as a handgrip raises both pressures instead. A fall in systolic pressure during a treadmill test is abnormal and suggests severe ischaemia or left ventricular dysfunction.

   • B: Rising DBP and TPR are the pattern of sustained isometric exercise.
   • C: SBP rises with the rise in cardiac output; it does not fall in health.
   • D: SBP rises markedly in dynamic exercise; TPR falls, not rises.

5. Question 5 · Easy

   A 22-year-old woman with paroxysmal supraventricular tachycardia is asked in casualty to plunge her face into a bowl of ice-cold water while holding her breath. This manoeuvre produces:

   1. ATachycardia with peripheral vasodilation
   2. BTachycardia with peripheral vasoconstriction
   3. CBradycardia with peripheral vasodilation
   4. DBradycardia with peripheral vasoconstriction

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   Answer: D · Bradycardia with peripheral vasoconstriction

   Cold water on the face with breath-holding triggers the diving reflex. Trigeminal afferents increase vagal outflow to the heart, causing bradycardia, while sympathetic vasoconstriction reduces flow to the limbs and gut, conserving oxygen for the heart and brain. The vagal surge slows AV nodal conduction and can stop a re-entrant SVT, much like carotid sinus massage.

   • A: The reflex gives slowing and constriction, the opposite of both.
   • B: The reflex slows the heart through the vagus.
   • C: Peripheral vessels constrict, not dilate, to conserve oxygen.

6. Question 6 · Hard

   A 24-year-old long-distance runner from a Kerala athletics academy is compared with his sedentary identical twin in a physiology laboratory. Which of these are expected in the runner? 1. Lower resting heart rate 2. Larger resting stroke volume 3. Higher maximal oxygen uptake (VO2 max) 4. Higher maximal heart rate

   1. A1 and 3 only
   2. B1, 3 and 4 only
   3. C1, 2 and 3 only
   4. D2 and 3 only

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7. Question 7 · Medium

   A 34-year-old commercial diver working on an offshore oil platform off Mumbai surfaces rapidly from 40 m after his air supply fails. Within an hour he has deep, aching pain in both shoulders and knees and tingling in his legs. What is the next best step?

   1. ANormal saline and bed rest only
   2. BRecompression in a hyperbaric chamber
   3. CAnalgesics and rest in the ward
   4. DImmediate in-water recompression

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8. Question 8 · Medium

   A 21-year-old army recruit from Shimla is posted to the Thar desert. Which of these changes are expected after 2 weeks of daily training in the heat? 1. Sweating starts at a lower core temperature. 2. Sweat volume per hour increases. 3. Sodium concentration of sweat rises. 4. Plasma volume expands.

   1. A1 and 2 only
   2. B1 and 4 only
   3. C2 and 3 only
   4. D1, 2 and 4 only

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9. Question 9 · Medium

   A 30-year-old construction labourer carries loads of bricks up a staircase for an hour. Blood flow to his thigh muscles rises many-fold while flow to the gut falls. Which factor chiefly causes the vasodilation in the working muscle?

   1. ACirculating adrenaline acting on alpha receptors
   2. BCirculating vasopressin released in exercise
   3. CLocal metabolites such as K+, adenosine and CO2
   4. DSympathetic cholinergic vasodilator fibres

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10. Question 10 · Medium

    A 40-year-old construction worker in Nagpur collapses at 2 pm in May. Rectal temperature is 41.8 °C, he is confused and agitated, his skin is hot, pulse 136/min, BP 96/60 mmHg. What is the next best step?

    1. ARapid whole-body cooling with cold water
    2. BIV paracetamol to lower the set point
    3. COral dantrolene to stop heat production
    4. DOral ORS and rest in a shaded room

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