Micturition Flashcards
Describe the neurological control of urine STORAGE
- bladder stretch receptors detect stretching (bladder filling)
- the nerves from the stretch receptors enter spinal cord at S2-4 and travel up to T10-L2 & synapse w/ sympathetics
- Sympathetic nerve then leaves spinal cord, having been told the bladder is stretching and releases NA at neuromusclar junction w/ destrusor muscle, this inhibits destrusor contraction (relaxes it)
- it also goes to internal urethral sphincter & releases NA to cause contraction and maintiain continance
- The L centre in the brain is under conscious control, it sends fibres down spinal cord which tell pudenal nerve to stimulate EUS contraction via Ach release
Which sex has an internal urethral sphincter and what is its job?
Males, it prevents retrograde flow of ejaculate
Which receptors are found at:
- neuromusclar junction w/ sympathetics and destrusor muscle
- neuromusclar junction w/ parasympathetics and destrusor muscle
- internal urethral sphincter
- extenral urethral sphincter
- neuromusclar junction w/ sympathetics and destrusor muscle= B3 receptors
- neuromusclar junction w/ parasympathetics and destrusor muscle= M3 receptors
- IUS= A1 receptor (no parasympathetics)
- EUS= Ach receptor
How is voiding stimulated when bladder volume threshold is reached?
- Bladder stretch detectors reach threshold and synapses with parasympathetics in S2-4 region to say the bladders full
- Parasympathetics leave at S2-4 and stimulate detrusor contraction
- The parasympathetics are also stimulated and inhibited by the M centre, which is partly under conscious control so you get to decide if its a good time to wee or not
- The M centre gets info to decide whether to wee from the brain cortex (conscious contol) and also the stretch receptors
- The M centre also inhibits the L centre, which means less stimulation of the pudendal nerve (Opens EUS) and also inhibit sympathetics to bladder (relaces IUS and stops relaxation of bladder destrusor muscle)
Where in the brain is the M center?
the pons
What is the maximum capacity of the bladder and what is the vital capacity at which micturition is stimulated?
max capacity= 500ml
micturition stimulated @ 200-300 ml
What would be the result of a spinal cord transection anywhere within S2-4?
Youd loose parasympathetics (and sympathetics) but since you’ve lost parasympathetics youll get a flaccid bladder- it cant contract. As a result of this you get overflow incontenance because the bladder would just fill until pressure is greater than sphincter pressure and urine starts to leak
What would be the result of a spinal cord transection above T12?
Sensory and motor neurones are cut but the autonomic reflex arcs arnt. This means your filling and voiding reflexes are still intact, but youd have no conscious control over when you wee- called reflex bladder. Also IUS looses pudendal nerve stimulation.
Define incontinance?
Involuntary leakage of urine
What are the 4 broad types of incontinance?
Stress- involuntary leakage on effort, exertion, coughing or sneezing
Urge- leakage accompanied by or immediatly preceeded by urgency
Mixed- leakage associated with urgency and also with coughing, sneezing ect
Overflow
Whats the biggest cause of stress incontinance?
pregnancy/ vaginal delivery, age, obesity, chronic cough
How can stress incontinance be treated? (1st-3rd line)
1st- pelvic floor exersizes
2nd- surgery (slings and low tension vaginal tapes)
3rd- pharacological- NSRI to inhibit NA reuptake, this stimulates better contraction of the IUS and relaxation of the detrusor muscle.
What causes urge incontinance?
Overactive bladder syndrome, bladder cancer/ stones/ infections, neurological issues
How can urge incontinance be treated? (3)
1st- Bladder training (stop mid stream and also hold in as long as possible)
2nd- antimuscarinics (oxybutanine) to block bladder contractions
- B3 agonists to aid bladder relaxation
- Botox to prevent Ach release by parasympathetics at the neuromuscular junction
Other than sacral cord legions, what could cause overflow incontinance?
BPH
