Motility and peristalsis · Physiology

What is the primary effect of sympathetic nervous system stimulation on the sphincters of the gastrointestinal tract?

  1. Global relaxation to allow rapid transit
  2. Tonic contraction (increased tone)
  3. Rhythmic opening and closing
  4. Sympathetic nerves do not innervate GI sphincters
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Correct answer: Tonic contraction (increased tone)

In general, sympathetic stimulation inhibits the motility of the gut wall (via norepinephrine) but causes contraction of the sphincters (ileocecal, internal anal, etc.), effectively slowing the movement of contents during 'fight or flight'.

Difficulty: Medium Question 39 of 40

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