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Renal and Endocrine Biology > REB 32. Urinary Bladder and Micturition Reflex > Flashcards

REB 32. Urinary Bladder and Micturition Reflex Flashcards

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1
Q

What are the walls of the ureters made up of? What cells are present?

A
  • 2 smooth muscle layers in walls (circular + longitudinal)

- transitional epithelium lining

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2
Q

Why is the transitional epithelium lining in the ureters important?

A
  • it allows for stretch

- if the bladder is really full, the urine may enter the ureters (backflow)

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3
Q

Where does the ureter enter into the bladder?

A
  • bladder enters through the detrusor muscle in bladder trigone
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4
Q

What is the purpose of the middle circular layer of smooth muscle?

A

the circular muscle helps with contraction

- this moves the urine down the ureter

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5
Q

HOW does the ureter enter the bladder?

A
  • enters with OBLIQUE pathway through the detrusor muscle

- it crosses a large portion of the bladder

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6
Q

What does the tone of the detrusor muscle do? What is its function?

A
  • the ureter enters the bladder with oblique pathway through the detrusor muscle
  • tone of the detrusor muscle keeps the ureter compressed
  • as the bladder contracts, the ureter is compressed – it ensures that urine doesn’t flow back up through the ureters
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7
Q

What is the ureterorenal reflex?

A
  • the ureters are heavily innervated with pain fibres
  • blockage of the ureter causes build up of urine above the block and pain
  • this causes reflex activation of sympathetic nerves to the afferent arteriole
  • reduces blood supply to the kidney (to decrease urine coming out)
  • this decreases urine output
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8
Q

What is the vesico-ureteric reflux?

A
  • this may occur if the ureters do not enter the bladder in the right fashion
    OR
  • loss of muscle tone in bladder
  • there may be a short passage of the ureter through the bladder wall
  • bladder contration in microturition may NOT always occlude the ureters
  • there is urine left in bladder
  • reflux of urine is when urine goes back up the ureters
  • this may lead to renal damage
  • – swelling of the kidney due to buildup of urine (hydronephrosis)
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9
Q

What is the function of the bladder?

A
  • storage and periodic elimination of urine
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10
Q

What type of control is the bladder under?

A
  • regulated by neural control systems

- normally under voluntary control (learned behaviour!)

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11
Q

What type of muscle and cell types is the bladder made up of?

A

[1] Inner Transitional Epithelium

[2] Detrusor Muscle
- has 3 layers of smooth muscle

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12
Q

Where is the external urethral sphincter located?

A

located in the urogenital diaphragm

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13
Q

What type of innervation is the internal sphincter supplied by?

A
  • sympathetic + parasympathetic control

- involuntary control

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14
Q

What type of innervation is the external sphincter supplied by?

A
  • voluntary control

- in the urogenital diaphragm

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15
Q

What is the normal urine formation rate in the kidneys?

A

1mL/min

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16
Q

What volume remains in the bladder after microturition?

A

hopefully NONE

- if there is some urine left in the bladder, this means that there is some damage or deficiency

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17
Q

Explain how laplace’s law relates to the filling of the bladder.

A
  • as the volume increases in the bladder, the bladder gets stretched and the tension increases
  • – V = T
  • as the tension/volume increases, the pressure does NOT change though
  • the pressure does not change because the radius increases as well

Laplace Law: P = T/R
e.g. 1/1 = P
2/2 = P
- the ratio stays the same

18
Q

What are the 2 phases in bladder filling?

A

[1] Filling phase

[2] Voiding phase

19
Q

Explain the pressure change (or not) in the filling phase of the bladder

A

the pressure remains steady

20
Q

Explain the pressure change (or not) in the voiding phase of the bladder

A

the pressure quickly drops as the bladder CONTRACTS and the RADIUS DECREASES

21
Q

How full should the bladder be to feel:
[1] Awareness
[2] Urge to Void
[3] Pain

A

[1] Awareness
- 150 mL

[2] Urge to Void
- 300 mL

[3] Pain
- 600 mL

22
Q

What is the innervation of the external urethral sphincter?

A
  • pudendal nerve

- somatic nerve

23
Q

What is the innervation of the internal urethral sphincter?

A
  • vesical plexus
  • pelvic splanchnic nerve
  • – they both relax the sphincter

(and the hypogastric and vesical plexuses)
- it contracts the sphincter

24
Q

What is the innervation of the detrusor muscle?

A
  • hypogastric and vesical plexuses

* also innervates internal urethral sphincter

25
Q

What are the 4 components of the innervation of the bladder?

A

[1] Primary Afferent Neurons
[2] Spinal Efferent Neurons
[3] Spinal Interneurons
[4] Neurons in the brain that activate/modulate spinal reflex pathways
– note: the spinal reflex to urinate can be controlled through higher brain centres

26
Q

Explain the sympathetic nervous innervation of the bladder

A

innervation from the SYMPATHETIC CHAIN through the HYPOGASTRIC NERVES

27
Q

Explain the parasympathetic nervous innervation of the bladder

A

innervation through the PELVIC PLEXUS and directly to the BLADDER WALL

28
Q

Explain the somatic nervous innervation of the bladder

A

directly to EXTERNAL SPHINCTER from MOTOR NUCLEUS in the SPINAL CORD

29
Q

Explain the afferent nervous innervation of the bladder

A

fibres travel to SPINAL CORD via PELVIC HYPOGASTRIC and PUDENDAL NERVES

30
Q

What is the origin, nerves, neurotransmitter and receptor of the SYMPATHETIC efferents?

A

Origin:
- T10 to L4

Nerves:
- Hypogastric

Neurotransmitter:
- Noradrenaline (NA)

Receptor:

(a) Beta-3
- relaxes the detrusor muscle

(b) Alpha-1
- constricts/contracts the internal sphincter

31
Q

What is the origin, nerves, neurotransmitter and receptor of the PARASYMPATHETIC efferents?

A

Origin:
- S2 to S4

Nerves:
- Pelvic

Neurotransmitter:

  • Acetacholine (ACh)
  • Nitric Oxide (NO)

Receptor:
Muscarinic M3 ACh
- contracts the detrusor muscle
- relaxes the internal sphincter

32
Q

What is the origin, nerves, neurotransmitter and receptor of the PARASYMPATHETIC efferents?

A

Origin:
- S2 to S4

Nerves:
- Pudendal nerve

Neurotransmitter:
- Acetylcholine (ACh)

Receptor:

  • Nicotinic ACh
  • contracts the external sphincter
33
Q

Which branch of the autonomic nervous system richly supplies the bladder?

A

parasympathetic nerves

34
Q

Which branch of the autonomic nervous system only has sparse innervation of the bladder?

A

sympathetic nerves

35
Q

Explain the storage reflexes in the bladder that occurs during the filling/storage phase.

A
  • low level afferent firing from stretch receptors
  • organized by circuits in the spinal cord
  • inhibits parasympathetic activity which relaxes detrusor and contracts internal sphincter
  • signal sent to midbrain (pontine storage centre) increase external urethral sphincter activity and decrease parasympathetic activity
36
Q

What are some actions that occur during the void phase?

A
  • relaxation of urethral sphincters
  • contraction of detrusor muscle
  • increased bladder pressure
  • flow of urine
  • Valsalva Manoeuvre (forced expiration against a closed glottis)
  • – increases pressure in the whole abdomen and makes sure all urine comes out
37
Q

What is the Valsalva Manoeuvre?

A

forced expiration against a closed glottis

— increases pressure in the whole abdomen and makes sure all urine comes out

38
Q

Explain the steps/mechanical and biochemical process that is involved in the control of micturition

A
  • increased firing of afferents from bladder
  • signals to Rostral Brain Stem
  • processed in Periaqueductal Gray (PAG) and Pontine Micurition Centre
  • sensation of bladder fullness
  • if it is appropriate, conscious decisio to micturate is made
  • inhibition of the somatic (voluntary) pathway to the external sphincter
  • — External Sphincter Relaxation
  • activation of descending pathways to bladder and urethra
  • — Bladder Contraction and Internal Sphincter Relaxation
  • higher centre control is absent or deficient with cord injury, infants, dementia, intellectual disability
39
Q

When is the higher centre control absent or deficient?

A

those with cord injury, infants, dementia, intellectual disability

40
Q

What are the 2 types of spinal cord injury which leads to a loss of voluntary control?

A

[1] Areflexic

  • urinary retention
  • bladder doesn’t know it’s full - there are no signals sent to the brain

[2] Hyperreflexic

  • neurogenic detrusor overactivity
  • due to emergence of spinal mictourition reflex pathway

Renal and Endocrine Biology (25 decks)

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