9.6 Micturition; Autonomic Bladder Innervation; Renal Pathologies Flashcards

1
Q

When does the urge to urinate appear in terms of bladder capacity? What is max capacity?

A
  • Urge appears at 200mL
  • Bladder has capacity of approx. 700-800mL
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2
Q

At what capacity do detrusor muscle contractions force the internal urethral sphincter open?

A

~500mL

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3
Q

Under what situations will opening of the internal urethral sphincter result in micturition regardless of voluntary input?

A
  • Underdeveloped neural pathways for external sphincter control (e.g. infants)
  • Weakened external sphincter (e.g. elderly)
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4
Q

Describe the micturition reflex? What other process occurs?

A
  • Stretch receptors -> spinal cord -> internal sphincter opens and bladder contracts
  • Information also sent from spinal cord to brain, whereupon we can voluntarily open the external sphincter
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5
Q

Which vertebrae do the sympathetic nerves that innervate the bladder originate from? Which ganglia can these nerves synapse in?

A
  • Lower thoracic and upper lumbar
  • Synapse in paravertebral ganglia and inferior mesenteric ganglion
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6
Q

Which segments of the spinal cord do the parasympathetic nerves that innervate the bladder arise from? What plexus do the postganglionic neurons arise from?

A
  • Originate from sacral region of spine
  • Arise from the pelvic plexus or bladder wall itself
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7
Q

Which vertebrae do the somatic nerves that innervate the external urethral sphincter originate from? What nerves do they travel in?

A
  • S2-S4
  • Travel in pudendal nerves
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8
Q

What muscle makes up the bladder wall?

A

Detrusor muscle

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9
Q

Which type of autonomic innervation relaxes and contracts the bladder wall?

A
  • Sympathetic: relaxes
  • Parasympathetic: contracts
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10
Q

Describe the neurotransmitters, receptor types, and forms of innervation associated with the bladder

A

Parasymp: Ach (contract) -> M3 receptor
Symp: NA (relax) -> beta 3 receptor

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11
Q

Describe the neurotransmitter, receptor type, and form of innervation associated with the internal urethral sphincter

A

Symp: NA (contract) -> alpha 1 receptor

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12
Q

Describe the neurotransmitter, receptor type, and form of innervation associated with the external urethral sphincter

A

Somatic: ACh (contract) -> nicotinic receptor (like usual)

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13
Q

What are the three centres of control of micturition?

A
  • Cortical centre
  • Brainstem centre
  • Spinal cord
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14
Q

List some brain regions responsible for bringing micturition under voluntary control

A
  • Pontine micturition centre
  • Periaqueductal grey
  • locus coeruleus
  • Hypothalamus
  • Cingulate gyrus
  • Laracentral lobule
  • Frontal lobe
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15
Q

What are the two types of nervous system disease that can cause bladder dysfunction?

A
  • Central: Stroke, Spinal Cord Injury (SCI), ALS
  • Peripheral: Disc herniation
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16
Q

What is detrusor hyperflexia?

A

Involuntary, uninhibited contraction of the detrusor muscle

17
Q

What is detrusor sphincter dyssnergia?

A

Bladder outlet obstruction due to detrusor muscle contraction with urethral sphincter activation

18
Q

What is areflexia?

A

Detrusor muscle cannot contract - flaccid bladder

19
Q

What effects can suprapontine lesions have on bladder function? Why?

A
  • Detrusor hyperreflexia: involuntary, uninhibited detrusor contractions
  • Tonic inhibitory control of the spinal reflex pathway is lost
20
Q

What effects can spinal lesions above T12 have on bladder function?

A
  • Hyporeflexive bladder activity
  • Detrusor sphincter dyssynergia
21
Q

What effects can sacral lesions have on bladder function?

A
  • Acontractile bladder (failure to contract when full)
22
Q

What types of infections are UTIs?

A

Bacterial

23
Q

What regions are lower UTIs associated with? Are these uncomplicated or serious?

A
  • Lower: Bladder, urethra
  • Considered uncomplicated
24
Q

What regions are upper UTIs associated with? Are these uncomplicated or serious?

A
  • Upper: Ureters, kidneys
  • Considered more serious
25
Q

Why are UTIs more common in women?

A

Easier for bacteria to gain access due to shorter urethra

26
Q

What are kidney stones?

A

Crystallisations of salts and minerals in urine

27
Q

What causes kidney stones?

A

Excess calcium and dehydration (think: vitamin D supplementation)

28
Q

Provide a basic description of renal failure

A

kidneys cannot filter wastes from the blood and can no longer maintain homeostasis.

29
Q

What are some flow-on effects of renal failure?

A
  • Blood pressure increases
  • Anaemia develops (EPO decreases)
  • CNS problems
30
Q

What are the two types of renal failure?

A
  • Acute
  • Chronic
31
Q

Describe the differences between chronic and acute renal failure. In which situation can kidney function be regained?

A
  • Chronic occurs gradually, whereas acute occurs suddenly
  • Kidneys may regain function in acute failure, whereas progression can only be slowed in chronic failure
32
Q

What are some causes of acute renal failure?

A
  • Renal ischaemia
  • Urinary obstruction
  • Trauma
  • Nephrotoxic drugs
33
Q

What are some causes of chronic renal failure?

A
  • Unmanaged diabetes
  • Hypertension
34
Q

How can UTIs be resolved?

A
  • Drink lots of water to flush out urinary system
  • Antibiotics in more serious cases
35
Q

How does kidney dialysis work

A
  • Artificial membrane as opposed to glomerular filtration
  • Plasma proteins cannot ass through, but ions and waste can
  • Lost solutes can be added back into the machine