Explain micturition.
Urine formed by the nephrons is carried to the urinary bladder where it is stored until a voluntary signal is given by the central nervous system (CNS). The process of release of urine is called micturition.
The signal is initiated by the stretching of the urinary bladder as it gets filled with urine. In response, stretch receptors on the walls of the bladder send signals to the CNS. The CNS passes on motor messages to initiate the contraction of smooth muscles of the bladder and simultaneous relaxation of the urethral sphincter, causing the release of urine. The neural mechanism causing this is called the micturition reflex.
Explanation
The answer is derived directly from section 16.6 'Micturition' of the provided textbook context. It defines the process and explains the neural mechanism step-by-step: from the filling of the bladder and stimulation of stretch receptors to the processing by the CNS and the final muscular actions required for release. Key terms like 'micturition reflex', 'stretch receptors', and 'urethral sphincter' are included as they are essential for a complete 3-mark answer in NCERT exams.