Micturation Control Flashcards
Journey of the urine from kidney to bladder (contractions)
Peristaltic waves of contraction brings urine from the pelvis of the kidney to the bladder
What occurs when there is a sufficient amount of urine in the bladder
Stretch receptors sense this and cause reflex parasympathetic innervation of the DETRUSOR muscles of the bladder.
This coupled with the relaxation of the external sphincter muscles, allows urine to pass out the urethra and out of the body
What accelerates the process of urination?
Abdominal muscles voluntarily cause the forcing of urine out at a faster rate
Voluntary control of micturition is caused by
The descending spinal pathways inhibiting parasympathetic output
Additionally stimulating the somatic nerves for the continued contraction of the external urethral sphincter
What spinal damage can mean for micturition
Loss of voluntary control of urination
Inability to urinate, ie damage to parasympathetic nerves which supply detrusor muscles. (Ability to empty bladder efficiently is lost
Which 2 types of nerves report about bladder stretch?
Parasympathetic nerves Sympathetic nerves (hypogastric)
What muscles are the min contractile muscles in. The bladder?
DETRUSOR muscles
What effect does sympathetic nerves have in the DETRUSOR muscles?
Inhibitory
What effect does parasympathetic nerves have in the detrusor muscles
Excitatory effect
Which nerves are internal urethral sphincter muscles innervated by?
Sympathetic efferent
Noradrenaline release
What catecholamine is released by the somatic nerves when innervation the external sphincter muscle?
Acetylcholine
What innervates the external sphincter muscles of the urethra
The somatic motor fibres
What type of nervous innervation stimulates internal sphincter muscles?
Sympathetic or parasympathetic
Sympathetic (sympathetic efferent)
What type of nervous innervation stimulates external sphincter muscles?
Sympathetic or parasympathetic
Parasympathetic
Somatic nerves
What neurotransmitter is released by sympathetic nerves
Adrenaline
Noradrenaline
What neurotransmitter is released by parasympathetic nerves
Acetylcholine
Where do somatic nerves enter the spinal cord
S2 and S4
Where do the pelvic or parasympathetic nerves emerge
S2-S4
Where do the sympathetic nerves enter
T11-T12
What also detects stretch in the bladder
ICCs
Causes the micturation reflex
2 things
Bladder stretch leading to bladder contraction
What is the interface layer of the bladder?
MUSOCAL LAYER
What type of epithelium is in the mucosal layer of the bladder?
Transitional epithelium
Which layer of the bladder is sensory?
Submucosa layer
What type of layer is the detrusor layer of the bladder?
Contractile
What function do PONS have in micturition
Speak to higher brain centres
Inhibits parasympathetic efferent
Relaxes bladder
PREVENTS MICTURITION
Effect of full bladder on PONS
Pons stop inhibiting the parasympathetic efferent and allow contraction of detrusor muscles
What do pons do in voiding
Stop inhibiting:
Parasympathetic efferents to detrusor = detrusor contraction
Sympathetic efferent signals stopped= internal sphincter relaxes
Somatic efferent signals switched off by PONS= External sphincter relaxes
What is an Antonic bladder?
A dilated urinary bladdder that does not empty
What types of problems could lead to overflow incontinence
4 things
BPH (benign prostatic hyperplasia)
Sensory nerve damage during child birth
Anticholergnergic drugs ↓ parasympathetic
Epidurals ↓ sensation
Treatments for overflow incontinence (caused by ↓ parasympathetic innervation)
M3 Agonist
Catheterisation
Remove prostate
What is stress incontinence
Voiding of urine upon sneeezing, exercising, coughing
How does a weak pelvic floor cause stress incontinence
The external urethral sphincter doesn’t function effectively, leading to voiding on coughing/sneezing/exercise
Treatments for stress incontinence (Weakness of pelvic floor muscles and external sphincter)
Pelvic floor exercises, bladder training, ↓ fluid intake,
Artificial sphincter (external)
What is urge incontinence?
Overactive bladder, frequency and urgency day and night, with or without loss of bladder control
What causes overactive bladder? (Urge incontinence)
Oversensitivity due to UTI
Overstimulation of detrusor
Obesity, constipation, diabetes
Treatments for overactive bladder (think ↓ parasympathetic)
Antimuscarinic medications
Botulinum toxin (↓ AcH release)
Drink more water, bladder training
NSAIDs to ↓ inflammation
Neurogenic bladder dysfunction caused by
Spinal cord injury
Crush injury
Severance of ascending or descending inputs
What would happen if a patient had a T2 spinal cord injury
Overactive detrusor, due to no inhibitory influences above
External urethral sphincter unable to relax
Catheterisation needed
No voluntary control of micturition
How to reduce overactive voiding in neurogenic bladder dysfunction
Muscarinic antagonists
Botox or reduce AcH release
Desensitisation of ICCs with capsaicin
What is the function of capsaicin in neurological bladder dysfunction?
Desensitises the ICCs to stretch in the bladder
What does Botox reduce in parasympathetic neurones
Acetylcholine release
How are muscarinic antagonists used in treatment of bladder dysfunction/overfunction
Prevents parasympathetic stimulation of the DETRUSOR muscles, ↓ voiding potential
