What is the effect of increased parasympathetic tone on the bladder?

• A. Inhibits sphincter and activates detrusor (correct)
• B. Inhibits detrusor and contracts sphincter
• C. No effect on bladder
• D. Increases bladder capacity

Answer: (C)

Parasympathetic input to the bladder promotes emptying. Nerves from the pelvic floor release acetylcholine that stimulates muscarinic receptors on the detrusor muscle, causing it to contract. At the same time, parasympathetic activity relaxes the internal urethral sphincter, lowering outlet resistance and allowing urine to flow. The external sphincter is under somatic control and not directly driven by parasympathetic tone. So, increased parasympathetic tone leads to detrusor contraction and sphincter relaxation, not to increased bladder capacity.