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Physiology > Exam 4: Micturition > Flashcards

Exam 4: Micturition Flashcards

1
Q

What is micturition?

A

2 stage process that results in the passage of urine out of the body

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2
Q

What are the 2 stage of micturition?

A

Passive storage phase

Active voiding phase

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3
Q

What is the detrusor muscle?

A

Smooth muscle that is essential for voiding

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4
Q

What happens when the detrusor muscle contracts?

A

It increases pressure in the bladder to 40-60 mmHg

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5
Q

Describe the bladder wall layers

A

Transitional cell epithelium that maintains a barrier despite expansion and contraction of the bladder

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6
Q

Describe urine transport in the kidney

A

Urine leaving the collecting ducts is the final product and undergoes no further changes as it is transported to the bladder
Urine flow stretches calyces which increases their inherent pacemaker
Peristaltic contractions result

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7
Q

What is the ureter composed of?

A

Smooth muscle and a plexus of neurons that coordinate peristalsis

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8
Q

Where do the ureters enter the bladder?

A

At the trigone, coursing obliquely through the detrusor muscle

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9
Q

What does the normal detrusor tone do?

A

Prevents the back flow of urine

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10
Q

What is the vesicoureteral reflex?

A

Inappropriate backflow of urine into the ureter

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11
Q

What is the micturition reflex?

A

Autonomic spinal cord reflex that can be inhibited or facilitated by centers in the brain

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12
Q

Describe storage for micturition

A

Detrusor muscle: relax

Urethral sphincter: contract

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13
Q

Describe voiding

A

Detrusor muscle: contract

Urethral sphincter: relax

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14
Q

What are the nerves involved in micturition?

A

Hypogastric
Pelvic
Pudendal

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15
Q

What is the hypogastric nerve responsible for?

A

Sympathetic stimulation

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16
Q

What does the hypogastric nerve go to?

A

Detrusor muscle

Internal urethral sphincter

17
Q

What does the hypogastric nerve to the detrusor muscle do?

A

Causes relaxation via beta 3 adrenergic receptors

18
Q

What does the hypogastric nerve to the internal urethral sphincter do?

A

Causes tightening via alpha 2 adrenergic receptors

19
Q

What is the pelvic nerve responsible for?

A

Parasympathetic stimulation
Sensory
Forms a reflex arc

20
Q

What does the parasympathetic stimulation of the pelvic nerve go to?

A

Detrusor muscle

21
Q

What does the pelvic nerve to the detrusor muscle do?

A

Causes contraction via muscarinic cholinergic receptors

22
Q

What does the pelvic nerve do for sensory?

A

From the detrusor muscle

Detects stretching

23
Q

What does the pudendal nerve do?

A

Somatic to the external urethral sphincter and pelvic floor

24
Q

What does the pudendal nerve do to the external urethral sphincter and pelvic floor?

A

Causes contraction via nicotinic cholinergic receptors

25
Q

What happens in the storage phase?

A

Stretch receptors in the bladder wall send afferent signals along the pelvic nerve
Activates a reflex arc through the hypogastric nerve, which relaxes the detrusor muscle and increases urethral tone
Voluntary contraction of the external sphincter

26
Q

What is the micturition reflex a complete cycle of?

A

Progressive and rapid increases in bladder pressure
Period of sustained maximal pressure
Return of pressure to baseline

27
Q

What are the 2 possible outcomes for the micturition reflex?

A

Unsuccessful (no pee)

Successful (pee)

28
Q

What happens to cause an unsuccessful micturition reflex?

A

Reflex wasn’t strong enough to overcome control of the external sphincter
Period of inhibition ensues
Cycle starts over but increases in strength

29
Q

What happens to cause a successful micturition reflex?

A

Once the reflex is strong enough, it sends a reflex via the pudendal nerve to inhibit the external sphincter

30
Q

What happens in the voiding phase?

A

Micturition reflex takes over

Bladder completely empties

31
Q

What happens when the micturition reflex takes over in the voiding phase?

A

Detrusor muscle contracts via pelvic nerve stimulation

Urethral sphincters relax through blockage of the hypogastric and pudendal nerve

32
Q

What can the micturition reflex be inhibited or facilitated by?

A

The brain stem and cerebral cortex

33
Q

What is the inhibitory voluntary control achieved by?

A

Increasing tone in the external urethral sphincter

Physiology (70 decks)

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