Urination, which is also known as the process of micturition, is defined as a reflex action. This action excretes urine from the body, which carries the liquid wastes from the body. A vast combination of voluntary and involuntary functions combines to create the process of urination.

Stimulus from the bladder sends various nerve impulses to numerous areas of the body to ensure proper elimination. In a child’s body, urination occurs as a reflex when the urinary bladder is filled.


Voluntary control of the urinary bladder reflex is a learned process. In order to accomplish voluntary control, a child must have properly developed inhibitory ability within the cerebral cortex and spinal cord maturation.

The average adult produces about 1200 milliliters of urine daily. The bladder can generally contain approximately 700 to 800 milliliters of urine before drainage is required. At 200 to 300 milliliters of urine, the bladder will distend and begin to provide discomfort.


Image: Urination

The second, third, and forth sacral segments of the spinal cord are responsible for receiving the stimulation produces by a stretched bladder. This is where the micturation reflex center is located. Once the stretch receptors have discerned the sensation of being full and have sent the necessary impulses through the spinal cord to the various parts of the body, the nerves respond by stimulating the detrusor muscle and the internal urethral sphincter muscle.

Rhythmic contraction of the bladder walls and relaxation of the internal urethral sphincter present the urge to urinate. Voluntary control remains over the stimulated reflex response in healthy adult bodies. Voluntary control exercises the brain’s ability to activate the motor nerve fibers which permits the external urethral sphincter to relax. Hence, the brain can then permit complete relaxation of the sphincter muscles and the natural process of urination occurs.
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