Piss on legs
Once the voluntary signal to begin voiding has been issued, neurons in pontine micturition center fire maximally, causing excitation of sacral preganglionic neurons.
The firing of these neurons causes the wall of the bladder to contract; as a result, a sudden, sharp rise in intravesical pressure occurs.
In the case of the bladder, the tension increases as the organ fills, but so does the radius.
The hyperactive state in the former condition suggests the development of denervation hypersensitization even though the neurons interrupted are preganglionic rather than postganglionic.
The physiology of micturition and the physiologic basis of its disorders are subjects about which there is much confusion, especially at the supraspinal level.
For smaller mammals a different phenomenon occurs, where urine is discharged as droplets, and urination in smaller mammals, such as mice and rats, can occur in less than a second.
Voluntary contraction of the abdominal muscles aids the expulsion of urine by increasing the pressure applied to the urinary bladder wall, but voiding can be initiated without straining even when the bladder is nearly empty.
February Learn how and when to remove this template message There are three major types of bladder dysfunction due to neural lesions:
After transection of the brain stem just above the pons, the threshold is lowered and less bladder filling is required to trigger it, Piss on legs, whereas after transection at the top of the midbrain, the threshold for the reflex is essentially normal.
The flow of urine through the urethra has an overall excitatory role in micturition, which helps sustain voiding until the bladder is empty.