08.1 Control of Micturition

Question 1

What nervous systems act on the bladder?

Answer 1

Autonomic and somatic.

Question 2

What autonomic nerves act on the bladder and what is their action?

Answer 2

Sympathetic - Hypogastric n. (T12-L2) - relaxes detrusor + contracts internal urethral sphincter
Parasympathetic - Pelvic n. (S2-S4) - contracts detrusor + relaxes internal urethral sphincter

Question 3

What somatic nerve acts on micturition and what does it innervate?

Answer 3

Pudenal n. - (S2-S4) - Innervates the external urethral sphincter.

Question 4

What is the bladder stretch reflex?

Answer 4

Primitive reflex that occurs in young infants before toilet training?

Question 5

What is the bladder stretch reflex arc?

Answer 5

Bladder fills - sensory neurones detect stretch - this is relayed to the spinal cord
Interneurones relay this signal to the parasympathetic deferents (pelvic nerve)
Pelvic nerve causes the detrusor to contract and stimulate micturition

Question 6

What happens in adults instead of the bladder stretch reflex arc?

Answer 6

The interneurones don’t relay it straight to the parasympathetic neurones
The information is instead sent to the brain where the cortex processes it
It is then sent to the pons in the brain which stimulates or inhibits micturition

Question 7

What happens if the sympathetic flow is damaged?

Answer 7

Failure to store

Incontinence

Question 8

What happens if parasympathetic flow is damaged?

Answer 8

Failure to void which leads to overflow incontinence

Question 9

What happens in childbirth that commonly leads to incontinence?

Answer 9

Damage to the pelvic floor muscles or the pudenal nerve.

This can prevent the external urethral sphincter from closing.

Question 10

What are the two phases that neural control switches between?

Answer 10

Storing urine

Voiding urine