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Physiology

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Kidney

Question
9 out of 26
 

In micturition reflex, the first change to occur is: (DNB June-2010)



A Trigone relaxation

B Detrusor contraction

C Relaxation of perineal muscle

D Decreased urethral pressure

Ans. C Relaxation of perineal muscle

I. The first stage of the act of micturition is a relaxation of the perineal muscles, except the sphincter urethrae, and a contraction of the muscles of the abdominal wall Q.

II. This is followed by a firm contraction of the detrusor and relaxation of the sphincter vesicae.

III. The flow of urine begins on subsequent relaxation of the sphincter urethrae, the bladder being emptied by the contraction of the detrusor assisted by the action of the muscles of the abdominal wall.

IV. As the act is completed, the bladder muscles relaxes and the sphincter vesicae contracts.

V. Finally the sphincter urethrae are closed and (in males) the last drops of urine are expelled from the bulbar portion of the urethra by the action of bulbospongiosus.

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