10 innervation

the bladder receives input from both the autonomic (sympathetic and parasympathetic) and somatic arms of the nervous system

the sympathetic nervous system communicates with the bladder via the hypogastric nerve (T12 – L2), they innervate the;

the detrusor muscle

trigone region and

internal urethral sphincter

sympathetic stimulation relaxes the detrusor and contracts the bladder neck at the internal

sphincter via β and α receptors respectively

the parasympathetic nervous system communicates with the bladder via the pelvic

nerve (S2-S4), they innervate the

detrusor muscle

trigone and

internal urethral sphincter

parasympathetic activity contracts the detrusor muscle and relaxes the trigone and sphincter

the somatic nervous supply gives voluntary control over micturition. It innervates the external urethral sphincter, via the pudendal nerve (S2-S4). The motor neurons are located

in Onuf's nucleus, in the ventral horn of the

sacral spinal cord

in addition to the efferent nerves supplying the bladder, there are sensory (afferent) nerves that report to the brain. They are found in the

bladder wall and signal the need to urinate

when the bladder becomes full