Pontine micturition center

The Pontine micturition center (PMC, also known as Barrington's Nucleus) is a collection of cell bodies located in the rostral pons in the brainstem that is involved in the supraspinal regulation of micturition (urination). The PMC makes connections with other brain centers to control micturition, including the hypothalamus, the cerebral cortex and periaqueductal gray (PAG). The PAG in particular acts a relay station for ascending and descending bladder information from the spinal cord.

Regulation
In humans, neurons in the PMC send descending projections to Onuf's nucleus and to the parasympathetic nucleus in the spinal cord while receiving ascending input from the level of the sacral and lumbar cord. During bladder filling, neurons within the PMC are turned off, but at a critical level of bladder distention, the afferent activity arising from mechanoreceptors in the bladder wall switches the PMC on and enhances its activity. This activation results in relaxation of the urethra and contraction of the bladder due to concomitant stimulation of parasympathetic and inhibition of sympathetic outflow to the bladder, as well as removal of somatic activation of the external urethral sphincter. This pattern of activity can also be elicited through the conscious desire to void.