Micturition

Question 0

Action of sympathetic innervation to bladder? Which receptors and neurotransmitter?

Answer 0

Relaxation of detrusor muscle via β3 receptors in the fundus using noradrenaline
Contraction of internal urethral sphincter via α1 receptors using noradrenaline
Prevents micturition

Question 1

Sympathetic innervation of the bladder?

Answer 1

Hypogastric nerve (T12-L2)

Question 2

Parasympathetic innervation to bladder?

Answer 2

Pelvic nerve (S2-4)

Question 3

Effect of the parasympathetic nervous system on the bladder and how?

Answer 3

Increased signals cause contraction of detrusor muscle
Acetylcholine acts on M3 receptors
Causes micturition

Question 4

Somatic innervation of the bladder?

Answer 4

Pudendal nerve (S2-S4)

Question 5

Effect of somatic innervation in bladder?

Answer 5

Causes constriction/relaxation of external sphincter

Ach acts on nicotinic receptors

Question 6

What does sensory innervation of the bladder do?

Answer 6

Found in bladder wall and signals need to urinate wall is stretched
Afferent nerve fibres report to the brain

Question 7

At which point do you feel a full bladder?

Answer 7

400ml

Question 8

How is contraction of the detrusor muscle to void the bladder done?

Answer 8

Micturition centres in the brain act on micturition centres of the spinal cord which act on parasympathetic neurones.
Increase in parasympathetic stimulation causes contraction of the detrusor muscle, increasing intravesicular pressure

Question 9

Which part of the brain makes the conscious decision to urinate and how?

Answer 9

Cerebral cortex

Reduces somatic stimulation to the external urethral sphincter causing relaxation and urination

Question 10

What is the overall pathway from the brain to the bladder/sphincters to cause micturition?

Answer 10

Cerebral cortex - the Pons - sacral levels of parasympathetic outflow - detrusor muscle contracts and sphincter relaxes

Question 11

What happens to intravesicular pressure in the bladder as it fills?

Answer 11

Hardly changes because the rugae distend during filling

Question 12

What does an increase in sympathetic stimulation to the bladder cause?

Answer 12

Relaxation of detrusor muscle

Contraction of internal urethral sphincter

Question 13

How is an increase of sympathetic stimulation in the bladder done? How do you not wee?

Answer 13

Afferent nerves in the bladder transmit message that bladder is full
Goes to brain continence centres - spinal continence centres - sympathetic neurones
Cerebral cortex also increases somatic stimulation causing contraction of the external sphincter which also constricts the urethra