One function of parasympathetic nervous system is:

Appeared in: AIIMS Nagpur NO- 2020

Explanation

The parasympathetic nervous system (PNS) is responsible for 'rest and digest' activities, which conserve energy.
Pupil constriction (miosis) is a key function of the PNS, mediated by the oculomotor nerve (CN III) acting on the circular muscle of theiris.
This action reduces the amount of light entering the eye and is essential for focusing on near objects.

Option A: Contraction of hair muscles (piloerection or 'goosebumps') is a classic 'fight or flight' response mediated by the sympathetic nervous system.
Option B: Stimulation of most sweat glands is a function of the sympathetic nervous system, even though the postganglionic fibers are cholinergic.
Option C: Acceleration of the heartbeat (tachycardia) is a primary function of the sympathetic nervous system to increase cardiac output during stress or exercise.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Functions of the Parasympathetic Nervous System as background academic context rather than a clinical decision trigger.
Understanding the autonomic nervous system is crucial for nurses to predict and interpret patient symptoms and medication side effects. For example, anticholinergic drugs block PNS activity, leading to pupil dilation, dry mouth, and tachycardia.
What if? If a patient is given a cholinergic (parasympathomimetic) eye drop like pilocarpine for glaucoma, the nurse would expect to see pupil constriction (miosis) as the therapeutic effect, which helps increase aqueous humor outflow.

How to Approach the Question

First, identify the core concept: the question asks for a function of the parasympathetic nervous system (PNS).
Recall the mnemonic 'rest and digest' for the PNS and 'fight or flight' for the sympathetic nervous system (SNS).
Evaluate each option against this framework.
Contraction of hair muscles, stimulation of sweat glands, and acceleration of the heartbeat are all actions associated with stress or exertion ('fight or flight'), which are functions of the SNS.
Constriction of the pupil is an action that occurs during a state of rest, aligning with the 'rest and digest' functions of the PNS.
Therefore, select the option that fits the 'rest and digest' profile.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 2 p. 1444-1446

E6 Pharmacology Katzung 16e pp. 156-158, 174-176

Practise the full AIIMS Nagpur NO- 2020

Attempt every question from this paper in a timed mock, then review the full solution for each one.