Lecture 14 - Neurological Control Of Micturition Flashcards
What is the muscle that makes up the wall of the bladder?
Detrusor muscle (smooth muscle)
What is the function of the Internal Urethral Sphincter?
What type of muscle makes it up?
Mainly prevents retrograde ejaculation
Smooth muscle
Where is theExternal Urethral Sphincter located ?
What type of muscle makes it up?
In the pelvic diaphragm
Made of skeletal muscle
Does the pressure of the bladder increase as volume increases?
Why?
Not immediately due to the detrusor relaxing so the bladder distends
What volume of urine leads to the pressure of urine to start rapidly increasing?
150ml
What is the volume of urine at which the voiding stage is stimulated?
500ml
What are the 2 phases in urodynamics?
Storage phase
Voiding phase
What is the storage phase of urodynamics?
When the bladder increases in volume with no appreciable change in pressure
What is the voiding phase?
Where the rhythmic contractions oof the detrusor muscle enable voiding
Go to the last slide and draw a pressure volume graph for the bladder:
See above slide for correct graph
What are the important spinal nerves in the control of micturition?
Look at the last slide at image 1 to label:
T10
L2
S2
S4
What is the importance of T10 to L2 in micturition?
The sympathetic region of the spinal cord involved in micturition
What is the importance of S2, S3 and S4?
S2, S3 and S4 keeps your Ps off the floor
Piss
Poo
Penis
Nerves for pelvic function
What type of nervous system control is the Storage phase generally under?
Sympathetic
S for storage + sympathetic
What type of nervous system control is the Voiding phase under?
Parasympathetic
Peeing = Parasympathetic
Where do the stretch receptors sensory neurones enter into the spinal cord?
Same for both storage and voiding phase
S2, S3 and S4
Once the sensory neurone from the bladder has entered into the spinal cord at the region of S2 - S4 in the STORAGE system what then happens?
Ascends and Synapses to a sympathetic neurone at level T10 - L2
Or continues to ascend to synapse at the cerebrum telling us how full the bladder is
What 2 structures does the sympathetic neurone leaving the spinal cord synapse to?
(Storage phase)
Detrusor muscle
Internal Urethral sphincter
What is the receptor that the sympathetic neurone that leads to the detrusor muscle of the bladder?
B3
What affect does the sympathetics have on the detrusor muscle?
What receptor is this?
Inhibitory effect so prevents contraction of the detrusor muscle keeping the bladder relaxed so it can distend
B3
What is the receptor that is found on the internal urethral sphincter that the sympathetic neurone leads to?
alpha 1
What affect does the sympathetics have on the internal urethral sphincter? (Storage)
What receptor is involved?
Stimulates contraction of internal urethral sphincter
What is the important somatic motor neurone that sends messages to the external urethral sphincter / pelvic floor?
Pudendal nerve
What is the L centre?
Part of the storage part of urodynamics that helps prevent urination
L = Leave it for Later
Where is the L centre located?
Brain stem
What is nerve does the L centres neurone synapse to?
Pudendal nerve
What part oof the body does the pudenal nerve go to innervate?
External Urethral sphincter
What is the effect of the L centre synapsing to the pudendal nerve which innervates the external urethral sphincter?
Stimulates the contraction of the EUS maintaining continence
What is the receptor that the pudendal nerve acts on at the External Urethral Sphincter?
(Stimulated by the L centre)
What is the neurotransmitter for this?
nAChR (Nicotinic acetylcholine receptors)
Ach
What is the neurotransmitter for the sympathetic nerves for bladder control?
What receptors?
B3 (detrusor) = noradrenaline
A1 (IUS) = noradrenaline
Go to the last slide and draw on all the structures relevant to the storage phase
Look at the slide above to check
Should have sensory neurones that synapse with sympathetics which lead to the detrusor and IUS
L centre leading to pudendal to EUS
What type of neurone does the sensory neurone from the bladder synapse to at S2 - S4 in the voiding system?
Parasympathetic
What does the parasympathetic neurone in the voiding system synapse to?
Detrusor muscle
What affect does the parasympathetic nerves from the S2 - S4 region have on the detrusor muscle?
Stimulates detrusor muscle contraction
What is the receptor and the neurotransmitter that the parasympathetic neurones act on in the detrusor muscle of the bladder?
M3 receptor
ACh
What is the M centre?
Where is it located?
What is its function?
The micturition centre
In the brainstem
stimulates the parasympathetic neurone to stimulate the detrusor muscle to contract
What are the extra neurones that connect directly to the parasympathetic neurones form the brain?
Inhibitory neurones inhibiting parasympathetics preventing voiding
When is the M centre stimulated?
When the bladder stretches massively (sensory neurones)
Or when you decide that you want to urinate so neurones in cortex stimulate the M centre
Also neurones in cortex inhibiting M centre
How are the M centre and the L centre connected?
The M centre synapses onto the L centre to inhibit the L centre
Go the last slide and draw on all the relevant structures for the Voiding system:
Remember theres a connection between the M centre and L centre
