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MCAT Autonomic Nervous System Practice Questions: Sympathetic vs Parasympathetic

By StudyStore · Published 2026-11-04 · 8 original questions · about 12 min

Eight free MCAT-style practice questions on sympathetic and parasympathetic pathways, neurotransmitters, receptors and organ effects, with explanations.

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Quick concept primer

The autonomic nervous system controls involuntary functions through a two-neuron pathway: a preganglionic neuron from the central nervous system synapses in a ganglion with a postganglionic neuron that reaches the target. Preganglionic neurons in both divisions release acetylcholine (ACh) onto nicotinic receptors. Parasympathetic postganglionic neurons also release ACh, acting on muscarinic receptors. Sympathetic postganglionic neurons release norepinephrine on adrenergic receptors, with the exception of sweat glands, which use ACh.

The sympathetic division (fight or flight) arises from thoracolumbar spinal cord, has short preganglionic and long postganglionic fibers, raises heart rate, dilates bronchioles and pupils, and slows digestion. The parasympathetic division (rest and digest) arises from cranial nerves (including the vagus) and sacral cord, has long preganglionic and short postganglionic fibers, and slows heart rate and promotes digestion. The adrenal medulla acts like a modified sympathetic ganglion and releases epinephrine into blood.

8 practice questions

Try each question before opening the explanation. Click "Show answer and explanation" to check yourself. All questions are original and written for study practice.

Question 1

Which neurotransmitter is released by parasympathetic postganglionic neurons onto their target organs?

  1. Norepinephrine
  2. Epinephrine
  3. Dopamine
  4. Acetylcholine
Show answer and explanation

Answer: D. Acetylcholine

Both parasympathetic preganglionic and postganglionic neurons are cholinergic. The postganglionic neuron acts on muscarinic receptors at the target. Sympathetic postganglionic neurons usually release norepinephrine instead.

Question 2

Which statement correctly describes the preganglionic and postganglionic fibers of the sympathetic division?

  1. Long preganglionic and short postganglionic fibers
  2. Short preganglionic and long postganglionic fibers
  3. Both fibers are equally short
  4. Only a single neuron connects the spinal cord to the target
Show answer and explanation

Answer: B. Short preganglionic and long postganglionic fibers

Sympathetic ganglia lie close to the spinal cord in the sympathetic chain, so preganglionic fibers are short and postganglionic fibers are long. Parasympathetic ganglia lie near or inside target organs, so the pattern is reversed.

Question 3

The vagus nerve exerts which effect on the heart?

  1. Increases heart rate
  2. Decreases heart rate
  3. Increases contractile force through norepinephrine
  4. Has no effect on heart rate
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Answer: B. Decreases heart rate

The vagus nerve is the main parasympathetic nerve and releases acetylcholine on muscarinic receptors at the sinoatrial node, which slows the heart rate. Sympathetic stimulation increases heart rate and force of contraction.

Question 4

Which of the following responses is produced by sympathetic stimulation?

  1. Bronchoconstriction
  2. Increased peristalsis
  3. Pupil constriction
  4. Bronchodilation
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Answer: D. Bronchodilation

In fight or flight, bronchioles dilate to increase air flow, the pupils dilate, heart rate rises and digestion slows. Bronchoconstriction, increased peristalsis and pupil constriction are parasympathetic effects.

Question 5

The adrenal medulla is best described as

  1. a parasympathetic ganglion that releases acetylcholine into the blood
  2. a modified sympathetic ganglion whose cells release epinephrine and norepinephrine into the blood
  3. a gland that releases cortisol in response to ACTH
  4. part of the enteric nervous system
Show answer and explanation

Answer: B. a modified sympathetic ganglion whose cells release epinephrine and norepinephrine into the blood

Preganglionic sympathetic neurons synapse directly on chromaffin cells of the adrenal medulla, which act like postganglionic neurons but secrete mostly epinephrine into the bloodstream as a hormone. Cortisol comes from the adrenal cortex.

Question 6

A drug blocks nicotinic receptors at autonomic ganglia. Which outcome is most likely?

  1. Only parasympathetic transmission is blocked
  2. Only sympathetic transmission is blocked
  3. Neither division is affected
  4. Transmission through both sympathetic and parasympathetic ganglia is reduced
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Answer: D. Transmission through both sympathetic and parasympathetic ganglia is reduced

Preganglionic neurons in both divisions release acetylcholine onto nicotinic receptors on postganglionic neurons. A ganglionic blocker therefore weakens signaling in both pathways, and the effects depend on which division dominates a given organ.

Question 7

Sweat glands are an exception in the sympathetic division because their postganglionic neurons release

  1. norepinephrine
  2. epinephrine
  3. acetylcholine
  4. serotonin
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Answer: C. acetylcholine

Sympathetic postganglionic neurons that innervate sweat glands are cholinergic and act on muscarinic receptors. Most other sympathetic postganglionic neurons release norepinephrine, so sweat glands are a common exam exception.

Question 8

Which region of the central nervous system gives rise to parasympathetic outflow?

  1. Thoracic and lumbar spinal cord only
  2. Cerebellum
  3. Cranial nerves and sacral spinal cord
  4. Cervical spinal cord only
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Answer: C. Cranial nerves and sacral spinal cord

Parasympathetic fibers leave with cranial nerves III, VII, IX and X and with sacral segments S2 to S4, often called craniosacral outflow. Sympathetic outflow is thoracolumbar, from about T1 to L2.

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Written by StudyStore from standard scientific facts as a study aid. These are not official exam questions and are not affiliated with or endorsed by any testing organization. Always check values against the reference provided with your exam or course.

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