PBL 8 Flashcards
What is the uretorenal reflex?
Prevents excessive flow of urine into the pelvis of a kidney when the ureter is blocked
Pain nerve fibres supplying the ureters detect blockage and cause a sympathetic reflex back to the kidney to constrict renal arterioles, decreasing the renal output from the kidney
What is the vesicoureteral reflex?
This is where some urine in the bladder is propelled backwards into the ureters
This can lead to enlargement of the ureters
What is the voiding reflex?
This is where once you have started to expel urine from the bladder, sensory signals are sent to the sacral plexus
This further stimulates signals through the pelvic splanchnic nerve to cause contraction of the detrusor muscle until the bladder is empty
How much urine remains in the bladder after micturition?
Less than 10mL
How can higher centre control prevent micturition?
Firing signals through the voluntary pudendal nerve
This causes continual tonic contraction of the external sphincter until a continent time presents
What is the parasympathetic control of micturition?
Pelvic splanchnic nerve arises from S2-S4
Synpases on M3 receptor on bladder and releases ACh
This causes contraction of the detrusor muscle
What is the sympathetic control of micturition?
Hypogastric nerve arises from T10-L2
Synapses on B3 receptor on bladder and releases noradrenaline - this causes inhibition and relaxation of detrusor
Synapses on alpha 1 receptor on internal sphincter - causes contraction of sphincter
How does the bladder know when it is empty or full?
The amount of sensory signals coming from the bladder detects the stretch in the bladder wall - the more signals coming, the fuller the bladder is
Which part of the brain is responsible for controlling micturition?
Pons
What are the 4 types of urinary incontinence?
Urge incontinence
Stress incontinence
Overflow incontinence
Functional incontinence
What happens in urge incontinence?
You have an overactive bladder, which results in the sudden urge to urinate
Due to an uninhibited detrusor muscle which contracts randomly
What happens in stress incontinence?
Increased abdominal pressure overwhelms the sphincter muscles allowing urine to leak out
E.g, sneezing, coughing, laughing, during pregnancy
What happens in overflow incontinence?
Problem with emptying the bladder due to:
- blockage (e.g, BPH)
- ineffective detrusor muscle
- ineffective signalling
What is the function of the prostate?
Release alkaline fluid in semen to help neutralise acidity of the vagina
Contains smooth muscles that help to expel semen during ejaculation
What are the 4 zones of the prostate and where are they?
Central zone - surrounds the ejaculatory ducts
Transitional zone - centrally surrounds the urethra
Peripheral zone - posteriorly (largest zone)
Fibromuscular stroma - anteriorly
Which part of the prostate is most likely to undergo BPH?
Transitional zone
Which part of the prostate is most likely to undergo prostate carcinoma?
Peripheral zone