Micturation Flashcards
micturition sympathetic
hypogastric n
internal sphincter closes
action = filling
micturition somatic
pudendal n
external sphincter control
this is controlled by higher CNS input, so needs this to e turned off to urinate
Parasympathetic
Pelvic n.
contract bladder + contract internal sphincter muscle
ACh neurotransmitter nad muscarinic receptors
explain A1 and B2/B3 receptors on smooth muscle and detrusor m vs internal sphincter
adrenaline and noradrenaline act on a1, a2, b1, b2, b3
a = contract smooth muscles
B2 and B3 = relax smooth m (A2 CNA and B1 heart)
concentration of A2 and B2+B3 will determine if a smooth muscle relaxes or constricts under sympathetic stimulation
Detrusor m, has high B3 receptors
internal sphincter has high concentration of a1 receptors
Explain the micturition reflex
stretch receptors excitement initiates reflex contraction of smooth muscle
Reflex back to the bladder via parasympathetic nerve fibres of pelvic nerve
parasympathetic reflex = sacral spinal cord reflex
Detrusor muscle contracts
each contraction stimulates receptors, further and further contraction occurs (regenerating system) until bladder reaches a strong degree of contraction
After a few seconds to a minute the reflex begins to fatigue and the bladder relaxes, allowing it to fill more.
when micturition reflex is powerful enough a second reflex passes through to the pudenal nerves to external sphincter muscle to relax sphincter
urination occurs when the signal is stronger than voluntary contractor signals from brain urination will occur. brain overrides signal by not switching off the external sphincter muscle
problems with urination
extreme fear (sympathetic) olfactory fear signal - extreme flight
Atonic bladder
automatic bladder
Unibhibited neurogenic bladder
urge incontinence
stress incontinence
Overflow Incontinence
bladder not emptying properly (obstruction or neurogenic)
