8.1 Neuronal control of micturition

Question 1

purpose of IUS in males

Answer 1

prevent retrograde ejaculation

Question 2

how is bladder able to stretch so much?

Answer 2

rugae

Question 3

describe the ‘reflex’ storage phase

Answer 3

-stretch receptor in detrusor muscle detects bladder wall stretch, innervated by sensory neutron
-enters sacral cord S2-4, ascends to T10-L2
-synapses on sympathetic neuron
-pre then post ganglionic sympathetic goes to detrusor
-inhibitory effect on B3 receptors in detrusor, so bladder is relaxed
-stimulatory effect on alpha 1 IUS so stays closed

Question 4

describe the ‘cortical control’ storage phase

Answer 4

-stretcth receptors report to cerebral cortex, synapse
-L centre in brainstem sends neuron to pudendal nerve (somatic motor) S2-4
-pudendal nerve goes to EUS
-stimulatory effect ACh nicotinic receptor, keeps EUS closed

Question 5

describe the ‘reflex’ of voiding

Answer 5

-stretch receptor in detrusor detects stretch, innervated by sensory neurone
-enters spinal cord S2-4
-synapses on parasympathteic neurones
-project to detrusor
-excitatory effect on M3 ACh
-detrusor contracts

=void

Question 6

describe the ‘cortical control’ of voiding

Answer 6

-high levels of bladder stretch, sensory neurones activate M centre (medial to L centre)
-sends excitatory inputs to parasympathetics
-project to detrusor and contract it

positive feedback loop

Question 7

is the M centre autonomous?

Answer 7

no

Question 8

what happens when we really want to void?

Answer 8

M centre stimulated, sends inhibitor effects to L centre as pudendal nerve switches off so EUS relaxes