Which of the following is an effect of increased parasympathetic tone on the uterus?

• A. Contraction
• B. Inhibition of contraction
• C. Vasoconstriction
• D. Sensation from fundus of uterus

Answer: (B)

Increased parasympathetic activity tends to quiet smooth muscle, including the uterus, so it reduces the likelihood and strength of contractions. The parasympathetic nerves release acetylcholine, which acts on receptors in the uterine smooth muscle to dampen excitability and promote relaxation, leading to inhibition of contraction. This is contrasted with other autonomic influences that can promote activity in different tissues, and it explains why vasoconstriction or sensation from the fundus aren’t the primary effects of parasympathetic tone on the uterus. So the uterus becomes more quiescent when parasympathetic tone is higher, resulting in inhibited contractions.