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Flashcards in Micturition Deck (14)
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Sympathetic innervation of the bladder?

Hypogastric nerve (T12-L2)


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

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


Parasympathetic innervation to bladder?

Pelvic nerve (S2-4)


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

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


Somatic innervation of the bladder?

Pudendal nerve (S2-S4)


Effect of somatic innervation in bladder?

Causes constriction/relaxation of external sphincter
Ach acts on nicotinic receptors


What does sensory innervation of the bladder do?

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


At which point do you feel a full bladder?



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

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


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

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


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

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


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

Hardly changes because the rugae distend during filling


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

Relaxation of detrusor muscle
Contraction of internal urethral sphincter


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

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