Control of micturition Flashcards
What is micturition?
The normal process of the passive storage and active voiding of urine
How does urine move along the ureter?
Aided by peristalsis regulated by local smooth muscle
What prevents backflow of urine from the bladder?
Retrograde flow prevented by the oblique angle of entry through the bladder wall
What is the detrusor muscle? What is its nervous supply?
Network of smooth muscle fibres within the bladder wall, Supplied by both sympathetic and parasympathetic fibres
Where is the internal urethral sphincter? What is its nervous supply?
Thickening of the bladder musculature at the neck
Smooth muscle
Supplied by sympathetic supply
What is the external urethral sphincter? What is its nervous supply?
Striated muscle fibres
Under voluntary control of somatic nervous system
Caudal to internal sphincter
How does the bladder sense when its time to evacuate?
Stretch sensitive nerve endings in the bladder wall
Where does the motor supply to the external sphincter come from?
From S1-2 comes the pudenal nerve to innervate the external sphincter
Where does the parasympathetic supply to the detrusor muscle come from?
Is it excitatory or inhibitory?
S1-3 branches to the pelvic plexus which synapses in the bladder wall to the detrustor muscle
Neurotransmitter is ACh and it acts as excitatory
Where does the sympathetic supply to the detrusor muscle come from?
Is it excitatory or inhibitory?
L1-4 synapses at the caudal mesenteric ganglion (or bladder wall)
The neurotransmitter is norepinephrine, the receptor is beta adrenergic and action is inhibitory
Where does the sympathetic supply to the internal sphincter muscle come from?
Is it excitatory or inhibitory?
L1-4
Receptor is alpha adrenergic and the action is excitatory
These nerves go to where in the brain?
Control at the level of the pons and cerebral cortex.
What is the detrusor reflex?
Increased vesicular pressure with filling achieves threshold resulting in contraction of the detrusor muscle
Contraction occurs against urethral sphincter tone
What is the micturition reflex?
Combination of detrusor reflex with inhibition of sympathetic and voluntary motor supply to the bladder and urethra
What kind of feedback does the detrusor reflex have?
Positive - Once started usually continued until bladder emptied
