Nursing 2230A/B Lecture Notes - Lecture 12: Nephrostomy, Palpation, Oral Mucosa
17 Dec 2016
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Document Summary
The act of urination relies on the coordinated effort of the bladder and the urethral closure mechanism. The adult bladder normally holds approximately 500 ml of urine and empties, on average, five to seven times per day. As the bladder becomes distended and as it is deemed appropriate to urinate, the detrusor (bladder muscle) contracts and the urethral sphincter mechanism relaxes to allow expulsion of urine. As the bladder fills, sensory impulses are sent to the sacral spinal cord and relayed to the pontine micturition centre. If a person is ready to void, the pontine micturition centre relays the impulses back to initiate detrusor contraction, sphincter relaxation, and bladder emptying. If a person chooses not to void, the impulses are relayed to the cerebral cortex for voluntary inhibition of a detrusor contraction. If the urge to void has been ignored repeatedly, bladder capacity may be reached and the resulting pressure on the sphincter may make continued voluntary control impossible.
