What does the sympathetic nervous system control in the GI tract?

• A. Causes rapid peristalsis throughout the GI tract
• B. Sphincter muscles and movement within the alimentary canal, with an inhibitory effect that helps maintain continence
• C. Only increases digestive secretions
• D. Has no effect on the GI tract

Answer: (B)

The sympathetic nervous system reduces GI activity by inhibiting smooth muscle contractions and secretions, and by increasing the tone of many sphincters. This combination slows intestinal transit and helps maintain continence by keeping sphincters closed when needed. When activated, it suppresses movements like peristalsis and lowers secretions, while tightening sphincters along the alimentary canal. That inhibitory control over movement plus the increased sphincter tone is why this option best describes sympathetic influence on the GI tract. In contrast, rapid peristalsis and secretory increases are typically parasympathetic effects, and the sympathetic system does have a significant impact on the GI tract.