Micturition Flashcards
Define micturition?
. The normal process of the passive storage
and active voiding of urine
. Includes storage phase as well as the
voiding phase.
How is retrograde flow from the bladder into the ureters prevented?
. Retrograde flow prevented by the oblique angle of
entry through the bladder wall
The bladder is under what kind of control?
Involuntary. (smooth muscle)
The urethra is under what kind of control?
Urethra (voluntary an
Involuntary)
— Smooth muscle
— Skeletal muscle
What is the detrusor muscle?
A network of smooth muscle fibres within the bladder
wall. Supplied by both sympathetic and parasympathetic fibres.
What is the internal urethral sphincter?
. Thickening of the bladder musculature . Smooth muscle . Supplied by sympathetic supply
What is the external urethral sphincter?
. Striated muscle fibres
. Under voluntary control
of somatic nervous
system
What does the Parasympathetic supply
(cranio-sacral) to the bladder do?
Innervation — detrusor muscle
Neurotransmitter - ACh
Action — excitatory
Function — empty bladder
What does the Sympathetic supply to the
detrusor muscle allow?
. Neurotransmitter — Norepinephrine . Receptor - beta . Action — inhibitory on skeletal muscle fibres . Function — allows bladder filling
What is the detrusor reflex?
Increased vesicular pressure with filling achieves threshold resulting in contraction of the detrusor muscle involuntarily.
What does the positive feedback of the detrusor reflex achieve?
Once it has started positive feedback cause contractions to continue until the bladder is fully emptied.
This occurs at the SC level all a passive.
process.
The somatic motor supply outflows from S1-2 to form pudendal nerve it contains no synapses and Innervates the urethral skeletal muscle, specifically the External urethral sphincter. What function does this allow?
The retention of urine.
Sympathetic supply to the internaI sphincter outflows from L1-4. It synapses at the caudal mesenteric ganglion and innervates the internal sphincter. What function does this allow?
Retain urine, increase urethral
tone
What stimulates the micturition reflex in the voluntary state?
Intra abdominal pressure stimulates the micturition reflex in voluntary state.
A-adrenergic blocker do what?
Decrease sphincter tone by inhibiting the stimulatory outflow from L1-4 to the internal sphincter.