Neurological Control of Micturition Flashcards

1
Q

Describe the bladder

A

Smooth muscle bag – when contracts = empties

Control by the autonomic nervous system

Stores urine

Detrusor muscle = layer of the wall

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2
Q

Describe the internal urethra sphincter (IUS)

A

Smooth muscle

Well developed in men

Prevents retro-grade ejaculation = no semen enters the bladder

In DM the neural control of the sphincter is affected

Alpha 1 receptors

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3
Q

Describe the external urethral sphincter (EUS)

A

Skeletal muscle

Integral component of pelvic floor

Voluntary control

nAChR

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4
Q

What enables the bladder to increase in volume but pressure remains unchanged?

A

Expansion of smooth muscle

Storage phase until 500ml = pressure spike (max vol)

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5
Q

Outline the voiding phase of the bladder

A

Emptying

Contractions of the detrusor muscle = spikes as volume decreases

Relaxation of the IUS/EUS

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6
Q

Outline the neural control of the voiding phase (voiding reflex)

A

Parasympathetic

Stretch receptor bladder – sensory neurone to S2-S4 – synapse with parasympathetic neurones – parasympathetics project back to bladder = stim contraction of detrusor

M centre activated by HIGH bladder pressure (stretch receptors) = stimulate parasympathetics (+ve feedback)

Control of M centre = excitatory/inhibitory neurones

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7
Q

Outline the neural control of the storage phase (storage reflex)

A

Sympathetic

Stretch receptor in bladder – sensory neurone to S2-S4 – ascend up spinal cord – synapses between T10/L2 with sympathetic pre-ganglionic neurone – synapse with post-ganglionic neurones – to the detrusor muscle and IUS = inhibit contraction of detrusor + stim IUS

From the L centre (pons) excitatory neurones – synapse with motor neurones - from S2-S4 = somatic motor neurones (run along pudendal N) = innervates EUS = close

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8
Q

How does the M centre and L centre communicate?

A

When the M centre is activated = inhibition of L centre + sympathetics = voiding

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9
Q

What receptors are present on the IUS?

A

Alpha 1

Alpha 1 antagonists = relaxation of IUS = facilitate urination

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10
Q

What receptors in the bladder are inhibitory (storage reflex)?

A

Beta 3

Beta 3 agonist = inhibit overactive bladder

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11
Q

What receptors in the bladder are involved in the voiding reflex?

A

M3

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12
Q

What occurs in spinal cord lesions above S2 with regards to micturition?

A

Loss of inhibition of the stimulatory parasympathetic (voiding) reflex

Bladder overdrive = urination

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13
Q

What occurs in a spinal cord lesion between S2-S4 with regards to micturition?

A

Can no longer sense that the bladder is full = perpetual storage phase = bladder so big = incontinence

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