Micturition, also known as urination or voiding, is the process of the body expelling urine from the urinary bladder. It’s a regulated process involving the bladder’s muscle contractions, sphincter relaxation, and nerve signals. The urge to urinate arises when stretch receptors in the bladder send signals to the brain, triggering a reflex that initiates bladder emptying.
Urine Storage:
Urine is produced by the kidneys and collected in the urinary bladder, which can store a significant amount of fluid.
Bladder Filling:
As the bladder fills, stretch receptors in its walls are stimulated, increasing their firing rate.
Urge to Urinate:
This stimulation triggers the micturition reflex, which is the urge to urinate.
Micturition Reflex:
The reflex involves the contraction of the detrusor muscle (the bladder’s muscle) and the relaxation of the internal urethral sphincter, allowing urine to flow out of the bladder.
Voluntary Control:
While the micturition reflex is involuntary, humans also have voluntary control over urination, allowing them to delay or postpone urination based on social and situational factors.
Coordination:
The micturition process involves a complex interplay between the bladder, the internal and external urethral sphincters, and the nervous system.