Micturition

Autonomic and voluntary innovation

Detrusor contraction is parasympathetic

The parasympathetic connections are S2 S3 S4

Internal sphincter closed by sympathetic

Sphincter sympathetic activity reduces and parasympathetic increased to relax sphincter

External is voluntary, via pudendal nerve

Sympathetic supply to the bladder is L1 L2

Sensory supply is via the sympathetic L1 and L2 and via the parasympathetic S2 S3 S4

Bladder pressure remains much the same during filling

Sensory fibres relay information on distension

To empty impulses from the cerebral cortex increase parasympathetic and decrease sympathetic activity causing relaxation of the internal sphincter and contraction of the muscle

Reduction of pudendal activity relaxes the external sphincter

Diaphragm is lowered and abdominal muscles tighten to increase intrapelvic pressure