MCAT Behavioral Sciences Question 186: Answer and Explanation
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Question: 186
6. Acetylcholine is stimulatory to which of the following?
I. Skeletal muscle
II. Postganglionic neurons
III. Cardiac muscle
- A. I only
- B. I and II only
- C. II and III only
- D. I, II, and III
Correct Answer: B
Explanation:
Item I is true: acetylcholine is the neurotransmitter released by motor neurons onto skeletal muscle to cause contraction (choice C can be eliminated). Item II is true: the preganglionic neurons of both the sympathetic and parasympathetic nervous systems release acetylcholine onto the postganglionic neurons, triggering action potentials (choice A can be eliminated). Item III is false: acetylcholine on cardiac muscle is inhibitory and reduces the heart rate (choice D can be eliminated and choice B is correct).