Question at position 37 What role does the pontine micturition center play in the urine-voiding reflex?Relaxes the detrusor muscleEnhances sympathetic activityContracts the external urethral sphincterStimulates parasympathetic pathwaysInhibits somatic nervous system signaling

Question

BlackTom AI · Accepted Answer

Question examines the role of the pontine micturition center (PMC) in the urine-voiding reflex.

Option 1: 'Relaxes the detrusor muscle' — This is incorrect. The detrusor muscle contracts to expel urine during voiding; relaxation of the detrusor would promote retention, not voiding.

Option 2: 'Enhances sympathetic activity' — This is incorrect. Sympathetic activation supports storage of urine by relaxing the detrusor and contracting the internal sphincter. The PMC promoting voiding involves shifting away from storage mechanisms, not enhancing sympathetic tone.

Option 3: 'Contracts the external urethral sphincter' — This is incorrect. Contraction of the external (somatic) sphincter via the pudendal nerve aids continence and opposes voiding. During micturition, this sphincter is inhibited, not contracted.

Option 4: 'Stimulates parasympathetic pathways' — This is correct. The PMC coordinates micturition by activating parasympathetic (pelvic nerve) outflow to the detrusor muscle, causing its contraction and promoting bladder emptying. It also contributes to relaxation of the internal and external sphincters to facilitate voiding.

Option 5: 'Inhibits somatic nervous system signaling' — This statement is partially true in the sense that voiding involves relaxing the somatic pudendal pathway to the external sphincter, but as a standalone description it is incomplete and imprecise. The PMC’s key action is to stimulate parasympathetic activity; the indirect inhibition of somatic signaling is a downstream effect rather than the primary role described here.

In summary, the PMC primarily drives the voiding reflex by activating parasympathetic pathways to trigger detrusor contraction and by reducing somatic somatic (pudendal) input to the external sphincter, aligning with the correct option: 'Stimulates parasympathetic pathways'.

Question at position 37 What role does the pontine micturition center play in the urine-voiding reflex?Relaxes the detrusor muscleEnhances sympathetic activityContracts the external urethral sphincterStimulates parasympathetic pathwaysInhibits somatic nervous system signaling单项选择题

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