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MCAT Question A Day - 4/21/14 - Answer!

Arrector pili muscles are smooth muscles associated with hair follicles in the skin. When contracted, the muscles pull the hairs erect and “goose bumps” appear as the skin around the hair shafts slightly elevates. What stimulates the arrector pili muscles to contract?

A.  Somatic motor neurons
B.  Autonomic motor neurons
C.  Exocrine secretions
D.  Endocrine secretions

The correct answer is (B). Broad knowledge of the functions of the nervous and endocrine systems is helpful. The main point is that the arrector pili muscles are described as “smooth muscles.” These are involuntary muscles that are under the direct control of the autonomic nervous system.

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