Which of the following statements is correct?

Question

BlackTom AI · Accepted Answer

The question asks which statement is correct about micturition and its neural control.
Option A: 'Contraction of the detrusor muscle prevents voiding' — This is incorrect. Detrusor contraction is the primary motor event that drives voiding by increasing bladder pressure, not preventing it. In contrast, its relaxation during storage helps maintain continence.
Option B: 'For micturition to occur, the external urethral sphincter must be open and the internal urethral sphincter must be closed' — This is inaccurate. During micturition, the internal (smooth muscle) sphincter must relax (not stay closed) and the external (striated) sphincter must also relax to allow urine flow. Keeping the internal sphincter closed or the external sphincter actively open would impede voiding.
Option C: 'In adolescents, descending circuits from the pontine control centers (long reflexes) begin to override the spinal micturition reflex' — This statement is questionable. While descending control from the pontine micturition center modulates the spinal reflexes, the notion that adolescents uniquely begin overriding spinal reflexes at that stage is not a standard, well-supported description of maturation. The maturation and dominance of these pathways are typically described in broader developmental terms and not specifically limited to adolescence.
Option D: 'Long pontine reflexes can overcome local spinal reflexes to prevent micturition' — This is the best-supported option. Long (pontine) reflexes modulate and can override the local spinal micturition reflexes to regulate or inhibit voiding when appropriate, reflecting the role of higher brainstem control in urinary continence and timing of micturition.

Which of the following statements is correct?单项选择题

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