The process of release of urine is called micturition.
When the urinary bladder gets filled with urine, the stretch receptors present on the walls of the bladder send signals to the central nervous system (CNS).
In response to these signals, CNS sends the motor message which causes the contraction of smooth muscles of the bladder and simultaneous relaxation of the urethral sphincters. This results in the release of urine from the body.
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