Micturition

Micturition

Urination

Storage

Sympathetic nerves release norepinephrine through hypogastric nerve causing the detrusor muscle to relax and internal urethral spinchter muscle to contract involuntarily

Hypogastric Nerve

Sympathetic nerves responsible for urine storage, found in the spinal cord (T10-L2)

Urination

Parasympathetic nerves release acetylcholine using pelvic nerves to cause the detrusor muscle to contract and the internal urethral sphincter to relax involuntarily

Pelvic Nerve

Parasympathetic nerve responsible for urination, found in spinal cord integration center (S2-S4)

Stretch Receptors

Sensory receptors in bladder that send impulse to integration center when there is 150 mL + of urine in the bladder

Limbic System

Area in cerebrum that sends impulse to PMC when it is appropriate to urinate causing PMC to stimulate pelvic nerve and inhibit hypogastric voluntarily

Pontine Micturition Center

Area in pons that coordinates urination

Pontine Storage Center

Area in pons that coordinates urine storage

Cerebral Cortex

Outer region of the brain responsible for voluntary urination actions, allows the external urethral sphincter to relax

Parasympathetic Nerves

Nerves responsible for urination via acetylcholine using acetylcholine receptors, tell PMC and cerebral cortex when bladder is full and allows muscles to contract and relax

Sympathetic Nerves

Nerves responsible for urine storage via norepinephrine using adrenergic receptors

Micturition Reflex Center

Area in sacral spinal cord (S2-S4) that receives sensory impulses from stretch receptors, suppresses sympathetic impulses and activates parasympathetic impulses