Micturition

Question 1

Up to how many milliliters of urine can the bladder fill with before there is a drastic and rapid increase in pressure

Answer 1

300-400 ml

Question 2

Intravesicular pressure raises only slightly with increase in urine volume up to 300 ml because of what?

Answer 2

Intrinsic tone of the bladder wall

Question 3

Micturition contraction are the result of a stretch reflex initiated by sensory stretch receptors in which part of the bladder?

Answer 3

The bladder wall, especially by the receptors in the posterior urethra

Question 4

Sensory signals from the bladder stretch receptors are conducted through which nerves and to where

Answer 4

Sacral segments of the cord through the pelvic nerves and then reflexively back again to the bladder through the parasympathetic nerve fibers by way of these same nerves

Question 5

The micturition reflex is a single complete cycle involving which 3 things?

Answer 5

(1) progressive and rapid increase of pressure
(2) a period of sustained pressure
(3) return of the pressure to the basal tone of the bladder

Question 6

What kind of reflex is the micturition reflex?

Answer 6

Autonomic spinal cord reflex

Question 7

Which centers in the brain can inhibit or facilitate the micturition reflex

Answer 7

(1) strong facilitative and inhibitory centers in the brain stem, located mainly in the pons
(2) several centers located in the cerebral cortex that are mainly inhibitory but can become excitatory.

Question 8

Sympathetics allow filling of the bladder by doing what to the detrusor muscle and internal urethral sphincter?

Answer 8

Relaxes the detrusor muscle

Contracts the internal urethral sphincter

Question 9

Sympathetics act on which receptors to control the detrusor muscle, trigone and internal urethral sphincter

Answer 9

beta3 receptor for detrusor muscle

alpha 2 receptors for the trigone

alpha 1 receptors for internal urethral sphincter

Question 10

Parasympathetics allow what to happen to the detrusor muscle and what to the internal urethral sphincter?

Answer 10

The detrusor muscle contracts and the internal urethral sphincter relaxes

Question 11

Sympathetics act on which receptors to control the detrusor muscle

Answer 11

muscarinic 3 receptors

Question 12

Peristaltic contractions are in the ureter are enhanced by ______________
stimulation and inhibited by __________ stimulation

Answer 12

parasympathetic

sympathetic

Question 13

Which G protein and mechanism does sympathetic activation of alpha 1 receptors in the internal sphincter use to cause contraction?

Answer 13

Gq, IP3, DAG, Calcium-Induced Calcium-Release (CICR) mechanism

Question 14

Which G protein and mechanism does sympathetic activation of beta 3 receptors in the detrusor muscle use to cause relaxation

Answer 14

Gs, ↑cAMP, PKA mechanism

Question 15

Which G protein and mechanism does sympathetic activation of alpha 2 receptors in the internal sphincter use to cause contraction?

Answer 15

Gi, ↓cAMP, PKA mechanism

Question 16

Which G protein and mechanism does parasympathetic activation of muscarinc 2 receptors in the detrusor muscle use to cause relaxation

Answer 16

↓cAMP, PKA mechanism, inhibits voltage-gated Ca2+ channel, inhibits Ach exocytosis

Question 17

Which parasympathetic receptor on the detrusor muscle can be stimulated to produce relaxation

Answer 17

muscarinic 2 receptor

Question 18

Which G protein and mechanism does parasympathetic activation of muscarinc 3 receptors in the detrusor muscle use to cause contraction

Answer 18

Gq, IP3, DAG, CICR mechanism, with inhibition of Ca2+-activated K+ channel

Question 19

Which G protein and mechanism does parasympathetic activation of muscarinc 3 receptors in the internal sphincter and trigone use to cause relaxation

Answer 19

Gq, IP3, DAG, CICR mechanism activates NOS & release

Question 20

To relax the detrusor muscle and contract the internal urethral sphincter nerve fibers synapse in which ganglion in the cord segments?

Answer 20

Inferior mesenteric ganglion in segments T11-L2

Question 21

To contract the detrusor muscle and relax the internal urethral sphincter nerve fibers synapse in which ganglion in the cord segments?

Answer 21

Pelvic ganglion in segments S2-S4

Question 22

Sympathetic stimulation acts using which neurotransmitter to relax the detrusor muscle through ________ receptors

Answer 22

Uses norepinephrine or epinephrine

Beta 2 and 3 receptors

Question 23

The pudendal nerve causes constriction of the external urethral sphincter through release of which neurotransmitter on which type of receptor?

Answer 23

Acetylcholine on nicotinic receptors

Question 24

Which neuorotransmitter is released on M2 and M3 receptors by parasympathetic nerve to control the detrusor muscle

Answer 24

Acetylcholine

Question 25

Parasympathetic stimulation of the internal urethral sphincter causes release of which substance that leads to relaxation of the sphincter?

Answer 25

Nitric oxide

Question 26

An example of a non-cholinergic and non-adrenergic way of causing contraction of the detrusor muscle

Answer 26

ATP acting on P2XR, a nonselective cation channel

P2XR- a purinoreceptor, adenosine is a purine, allows Na+ and Ca2+ to go in

Question 27

Anticholinergic medication is sometimes ineffective for urinary urgency.
-why is this?

Answer 27

Muscarinic receptors, which would be blocked if an anti-cholinergic medication is given is needed for both relaxation and contraction of the bladder.

Question 28

What is the name of the area in the Pons where the micturition center is located

Answer 28

Barrington’s center

Question 29

Commands from the micturition center in the pons reach sacral regions of the spinal cord through with neural pathway

Answer 29

Reticulospinal tract

Question 30

How is the micturition reflex able to overcome the usual inhibitory commands of the brain

Answer 30

• Urine stretches the bladder
• activates the micturition center
• send signals to the sympathetic fibers, inhibiting them – activates the parasympathetic fibers
• contraction of the bladder which increases the the spinal loop of signals to the micturition center

Question 31

Stimulation of beta3 receptors ultimately cause an increase in PKA, how does this cause relaxation?

Answer 31

They phosphorylate K+ channels, this causes K+ channels to open and K+ leaves the cell resulting in hyperpolarization and thus relaxation

Question 32

Stimulation of alpha 2 receptors ultimately cause a decrease in PKA, how does this cause contraction?

Answer 32

They dephosphorylate K+ channels, this causes K+ channels to close and K+ stays in the cell resulting in depolarization and thus contraction