Control of Micturition

Question 1

• How is voluntary control of micturition achieved?

Answer 1

Suppression of the autonomic reflexes

Question 2

• What is peristalsis?

Answer 2

The movement of urine along the ureter

Question 3

• What muscle types are present surrounding the bladder and the urethra?

Answer 3

Bladder – smooth, urethra – smooth & skeletal

Question 4

• What is the difference between the internal and external urethral sphincters?

Answer 4

Internal – part of the detrusor muscle, smooth muscle, SNS supply
External – striated muscle fibres, under voluntary control of somatic NS

Question 5

• At what level is micturition controlled?

Answer 5

Control at the level of the pons and cerebral cortex

Question 6

• What is the detrusor reflex?

Answer 6

When increased vesicular pressure with filling reaches threshold causing contraction of the detrusor muscle

Question 7

• What is the micturition reflex?

Answer 7

Combination of detrusor reflex with inhibition of sympathetic and voluntary motor supply to the bladder and urethra

Question 8

• What are the four possible sites of actions for drugs effecting micturition?

Answer 8

Voluntary control of sphincter, PSNS to detrusor muscle, SNS to detrusor muscle, SNS to sphincter

Question 9

• What would be the effect of an α-adrenergic blocker?

Answer 9

Decreased sphincter tone

Question 10

• What would be the effect of an α-sympathomimetic?

Answer 10

Increased sphincter tone

Question 11

• What would be the effect of a skeletal muscle relaxant?

Answer 11

Decreased sphincter tone

Question 12

• What would be the effect of a parasympathomimetic?

Answer 12

Increased detrusor tone