Autonomic Nervous System Physiology — Integrated MCQs

Physiology · 36 free questions with answers & explanations.

1. A 55-year-old diabetic man is prescribed prazosin for hypertension. He develops orthostatic hypotension on standing. The normal reflex that prazosin disrupts is mediated by:
2. Physiologically, which neurotransmitter and receptor type mediates the effect of parasympathetic stimulation on sinoatrial node automaticity, and what is the ionic mechanism?
3. The 'mass discharge' of the sympathetic nervous system during intense stress ('fight-or-flight') produces a coordinated physiological response. Which combination of responses correctly represents the integrated sympathetic activation?
4. A patient taking a non-selective beta-blocker for hypertension develops significant bradycardia and bronchospasm during an asthma attack. Blocking which specific receptor subtype accounts for the bronchospasm?
5. Horner's syndrome (miosis, ptosis, anhidrosis) results from interruption of sympathetic pathways. A lesion of the first-order neuron (central pathway) would be located in:
6. A patient develops orthostatic hypotension with preserved heart rate response (no reflex tachycardia) upon standing. This pattern is most consistent with:
7. Stimulation of beta-2 adrenergic receptors in bronchial smooth muscle leads to bronchodilation. The intracellular signaling cascade involves:
8. The diving reflex (submersion reflex) in humans produces a characteristic cardiovascular response pattern. The correct description of this integrated autonomic response is:
9. A patient with pure autonomic failure has orthostatic hypotension but a normal heart rate response on standing. Which autonomic pathway defect explains this selective clinical pattern?
10. An anesthesiologist administers vecuronium (non-depolarizing NMJ blocker) and notes no pupillary changes, no change in heart rate, and no change in bowel sounds. Why does vecuronium not affect autonomic ganglia or the heart?
11. Stimulation of alpha-2 adrenoreceptors in the central nervous system produces which physiological effect that makes clonidine useful as an antihypertensive?
12. During a pharmacology experiment, a drug produces the following effects: bradycardia, increased GI peristalsis, bronchoconstriction, and pupillary constriction, but does NOT cross the blood-brain barrier. These effects are blocked by atropine. What is the drug's mechanism of action?
13. Orthostatic hypotension in a patient with pure autonomic failure (e.g., multiple system atrophy) is due to failure of which specific reflex arc?
14. A 68-year-old man with long-standing diabetes mellitus develops orthostatic hypotension (BP drop >20/10 mmHg on standing) with a fixed heart rate. This autonomic neuropathy is characterized by loss of which reflex arc?
15. During the Valsalva maneuver (forced expiration against closed glottis), which of the following sequences correctly describes the cardiovascular changes during phase II (sustained straining)?
16. Sympathetic stimulation of the kidney increases renin release via β1-adrenoceptors on juxtaglomerular cells AND causes direct renal vasoconstriction via α1-adrenoceptors. In a hemorrhagic shock patient on high-dose norepinephrine infusion, which of the following is the MOST likely renal consequence?
17. A 65-year-old diabetic man has orthostatic hypotension (BP drops from 130/80 supine to 90/60 standing) without a compensatory rise in heart rate. Which is the most likely site of autonomic dysfunction explaining the absent tachycardia?
18. Sweat glands are innervated by sympathetic nerves, yet the postganglionic neurotransmitter released at thermoregulatory (eccrine) sweat glands is acetylcholine rather than noradrenaline. This is an exception to the general rule of sympathetic neurotransmission. Which receptor subtype on eccrine sweat glands mediates their response?
19. During a Valsalva manoeuvre phase II (forced expiration against resistance), heart rate increases. The mechanism is:
20. A patient with Type 1 diabetes mellitus develops orthostatic hypotension, gastroparesis, and nocturnal diarrhoea. Autonomic testing shows absent heart-rate variability with deep breathing. This constellation is explained by:
21. Beta-2 adrenergic receptors in skeletal muscle blood vessels cause vasodilation. This response is mediated by:
22. Atropine blocks muscarinic receptors. In a patient given IV atropine 0.6 mg, the heart rate increases from 60 to 90 bpm. This tachycardia occurs because atropine removes:
23. Phenylephrine, a pure alpha-1 adrenergic agonist, is given IV to a hypotensive patient. Despite raising MAP, the heart rate falls (reflex bradycardia). This bradycardia is mediated by:
24. Horner syndrome results from interruption of the sympathetic supply to the face and eye. The complete triad includes ptosis, miosis, and anhidrosis of the face. The first-order neuron of the oculosympathetic pathway originates from:
25. A patient with autonomic neuropathy (e.g., in diabetes mellitus) has a fixed resting heart rate of 90 bpm with no change on standing or with the Valsalva maneuver. Which autonomic abnormality primarily explains this?
26. Horner's syndrome (ptosis, miosis, anhidrosis, and enophthalmos) results from interruption of sympathetic pathways to the head and eye. At which level of the three-neuron sympathetic chain would a lesion cause anhidrosis of the ipsilateral ENTIRE face and neck but spare the upper extremity?
27. Which of the following is the ONLY organ that receives ONLY sympathetic innervation (no parasympathetic supply) from the ANS?
28. A patient with a pheochromocytoma has paroxysmal hypertension, palpitations, and sweating. Which adrenoceptor mediates the vasoconstriction causing acute hypertensive episodes?
29. A 60-year-old man takes a non-selective beta-blocker for hypertension. During insulin-induced hypoglycemia, which sympathetic adrenergic symptom will be MOST effectively suppressed by his medication?
30. Stimulation of alpha-2 adrenergic receptors presynaptically at a sympathetic nerve terminal produces which effect?
31. A patient with complete T4 spinal cord transection (acute phase) is given IV atropine for symptomatic bradycardia. Why are patients with high cervical/thoracic spinal cord injury particularly prone to bradycardia and hypotension?
32. Which receptor subtype mediates bronchodilation when a selective beta-2 agonist is inhaled, and what is the intracellular second messenger responsible?
33. A patient takes a drug that blocks muscarinic M2 receptors in the heart. The expected physiological effect would be:
34. Horner's syndrome (miosis, ptosis, anhidrosis) results from interruption of the sympathetic chain. The finding of anhidrosis is limited to the face when the lesion is at which level?
35. During the diving reflex (triggered by cold water facial immersion), the coordinated autonomic response includes:
36. The adrenal medulla is considered a modified sympathetic ganglion. Unlike typical postganglionic sympathetic neurons, the chromaffin cells of the medulla predominantly secrete: