Exam 4: Micturition

Question 1

What is micturition?

Answer 1

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

Question 2

What are the 2 stage of micturition?

Answer 2

Passive storage phase

Active voiding phase

Question 3

What is the detrusor muscle?

Answer 3

Smooth muscle that is essential for voiding

Question 4

What happens when the detrusor muscle contracts?

Answer 4

It increases pressure in the bladder to 40-60 mmHg

Question 5

Describe the bladder wall layers

Answer 5

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

Question 6

Describe urine transport in the kidney

Answer 6

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

Question 7

What is the ureter composed of?

Answer 7

Smooth muscle and a plexus of neurons that coordinate peristalsis

Question 8

Where do the ureters enter the bladder?

Answer 8

At the trigone, coursing obliquely through the detrusor muscle

Question 9

What does the normal detrusor tone do?

Answer 9

Prevents the back flow of urine

Question 10

What is the vesicoureteral reflex?

Answer 10

Inappropriate backflow of urine into the ureter

Question 11

What is the micturition reflex?

Answer 11

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

Question 12

Describe storage for micturition

Answer 12

Detrusor muscle: relax

Urethral sphincter: contract

Question 13

Describe voiding

Answer 13

Detrusor muscle: contract

Urethral sphincter: relax

Question 14

What are the nerves involved in micturition?

Answer 14

Hypogastric
Pelvic
Pudendal

Question 15

What is the hypogastric nerve responsible for?

Answer 15

Sympathetic stimulation

Question 16

What does the hypogastric nerve go to?

Answer 16

Detrusor muscle

Internal urethral sphincter

Question 17

What does the hypogastric nerve to the detrusor muscle do?

Answer 17

Causes relaxation via beta 3 adrenergic receptors

Question 18

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

Answer 18

Causes tightening via alpha 2 adrenergic receptors

Question 19

What is the pelvic nerve responsible for?

Answer 19

Parasympathetic stimulation
Sensory
Forms a reflex arc

Question 20

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

Answer 20

Detrusor muscle

Question 21

What does the pelvic nerve to the detrusor muscle do?

Answer 21

Causes contraction via muscarinic cholinergic receptors

Question 22

What does the pelvic nerve do for sensory?

Answer 22

From the detrusor muscle

Detects stretching

Question 23

What does the pudendal nerve do?

Answer 23

Somatic to the external urethral sphincter and pelvic floor

Question 24

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

Answer 24

Causes contraction via nicotinic cholinergic receptors

Question 25

What happens in the storage phase?

Answer 25

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

Question 26

What is the micturition reflex a complete cycle of?

Answer 26

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

Question 27

What are the 2 possible outcomes for the micturition reflex?

Answer 27

Unsuccessful (no pee) | Successful (pee)

Question 28

What happens to cause an unsuccessful micturition reflex?

Answer 28

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

Question 29

What happens to cause a successful micturition reflex?

Answer 29

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

Question 30

What happens in the voiding phase?

Answer 30

Micturition reflex takes over | Bladder completely empties

Question 31

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

Answer 31

Detrusor muscle contracts via pelvic nerve stimulation | Urethral sphincters relax through blockage of the hypogastric and pudendal nerve

Question 32

What can the micturition reflex be inhibited or facilitated by?

Answer 32

The brain stem and cerebral cortex

Question 33

What is the inhibitory voluntary control achieved by?

Answer 33

Increasing tone in the external urethral sphincter