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Practice MCAT Question - Q108 - Answer!

Which statement is true about the autonomic nervous system?

A.  The sympathetic neurotransmitter, norepinephrine, speeds up all involuntary effectors.
B.  Norepinephrine speeds up some involuntary effectors and slows down others during “fight-or-flight” activities.
C.  Acetylcholine slows down some involuntary effectors and speeds up others during “normal” activities.
D.  B and C

The correct answer is (D). The sympathetic division of the autonomic nervous system regulates our involuntary effectors during situations such as stress and exercise (sometimes referred to as “fight-or-flight”). In such situations, norepinephrine speeds up cardiac muscle while slowing down the smooth muscle tissue of the digestive tract. In contrast, parasympathetic neurons, which release acetylcholine, will regulate these effectors as activities normalize. Thus, acetylcholine will slow down the heart back to normal, while speeding up the digestive processes back to normal.

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