The process of release of urine is micturition. The neural mechanisms causing micturition is called the micturition.
An adult human excretes on an average 1-1.5 litres of urine per day.
Mechanism of urine exeretion :
(a) Firstly, urine formed by nephrons is carried to the urinary bladder.
(b) In urinary bladder, it is stored till a voluntary signal is given by central nervous system (CNS).
(c) This signal is initiated by the stretching of the urinary bladder as it gets filled with urine.
(d) Now, the stretch receptors on the walls of the bladder send signals to the CNS.
(e) The CNS pass on motor messages to initiate the contraction of smooth muscles of the bladder.
(f) It results into the relaxation of the urethral sphincter
causing the release of urine.