Micturition

Question 1

Which of these nerves associates with parasympathetic, sympathetic or somatic NS?
-hypogastric
-pelvic
-pudendal

Answer 1

Hypogastric; sympathetic
Pelvic; parasympathetic
Pudendal; somatic

Question 2

3 steps of urinary bladder during micturition

Answer 2

Prevent urine escape (during bladder filling)
Allow urine Storage (relaxation of Detrusor wall)
Allow micturition-voiding

Question 3

Prevention of urine escape during bladder filling
-2 ways this is achieved

Answer 3

• using Internal sphincter (located at junction between Detrusor and urethra, smooth muscle)
  -as we stretch bladder, sphincter is stretched which causes it to close (not true anatomical sphincter)
  -involuntary control

-using external sphincter (located at end of urethra at skeletal muscle)
-Urethalis muscle contraction prevents urine flow
-voluntary control; signals are sent from brain down somatic nerve to contract
muscle, we can contract and close flow of urine

Question 4

Storage phase of micturition

Answer 4

-Detrusor should be relaxed so there is larger vol inside bladder
-Sphincter should be contracted so no leakage occurs

Question 5

Describe the process of relaxing the Detrusor during storage phase of micturition

Describe the process of contracting the sphincter during storage phase of micturition

Answer 5

Using sympathetic NS;

-hypogastric nerve runs down to Detrusor
-hypogastric n. Is stimulated and releases its neurotransmitter
-this causes inhibition of Detrusor which relaxes it and it expands

-parasympathetic NS activity is also inhibited
-pelvic n. Is inhibited at level of spinal segments S1-S3 by brain. Reflex centres
-cause Detrusor muscle to relax

-other fibres running from SNS to area closer to internal sphincter
-when these are stimulated it stimulates muscle contraction at level of sphincter

Question 6

Describe process of Micturition-voiding

Answer 6

-High activity of afferent fibres triggers reflex signals to come down which triggers efferent parasympathetic activity
-this causes contraction o Detrusor muscle of bladder
-hypogastric n. (sym) is inhibited, preventing relaxation
-this causes also inhibition of somatic pudendal nerve—> sphincter muscle relaxes and urethra opens

Question 7

Do dogs have any control as to when they pee?

Answer 7

Have some Voluntary control but when bladder gets too full and they can’t hold it at more, involuntary micturition will occur

Question 8

Urinary retention
-what is it

Answer 8

Incomplete emptying (or voiding) of urine, with no obstruction of the urinary tract,

Question 9

Causes for urine retention

Answer 9

Trauma, pelvic nerve, spinal cord
Spinal disease
Slipped disc in recumbent patients
No exchange of information between bladder and brain
Chronic bladder distention
Electrolyte disturbances
Neuropathy, midbrain disorders
Dysautonomia
Excessive adrenal steroids (Cushing’s
disease)

Question 10

Urinary incontinence
-definition

Answer 10

Involuntary loss of urine.

Question 11

Causes for Urinary incontinence

Answer 11

Age
Spay incontinence (Up to 80% bitches) Diabetes
Kidney disease
Nerve damage/trauma (local spinal, brain)
Urinary tract (usually bladder) infections
Overactive bladder syndrome
Pressure on the bladder caused by a mass

Question 12

How do we pharmacologically manipulate micturition

Answer 12

Via the Autonomic nervous system using receptors

Question 13

Receptors associated with sympathetic NS
Receptors associated with the parasympathetic NS

Answer 13

Adrenoreceptors- Noradrenaline/adrenaline receptors
Acetylcholine

Question 14

4 main adrenoreceptors

Answer 14

a1, a2, b1, b2

Question 15

a1 function
-stimulated by what NS

Answer 15

^ IP3 and DAG
Located near internal sphincter so stimulating a1 cause closure of sphincter
-sympathetic

Question 16

b2 function
-located where
-stimulated by what NS?

Answer 16

Increases or decreases cAMP
Located in Detrusor and causes its relaxation
-sympathetic NS

Question 17

a1
a2
b1
b2

Which of these are inhibitory and which are stimulatory

Answer 17

A1- stimulatory
A2- inhibitory
B1- stimulatory
B2- inhibitory

Question 18

2 types of parasympathetic cholinergic receptors

Answer 18

Nicotinic & muscarinic

Question 19

Nicotinic receptors
-type of ion movement
-stimulatory or inhibitory
-3 types
-difference between the 3 types

Answer 19

-ligand gated ion channels
-all stimulatory
-3 types depending on location;
1. Skeletal muscle receptors (Nm)
2. Gnaglionic receptors (Ng)
3. Brain receptors (Nn)

Differentially sensitive to drugs!

Question 20

Muscarinic receptors
-type of ion movement
-4 types
-each type stimulatory or inhibitory

Answer 20

-G protein coupled receptors
M1- stimulatory
M2- inhibitory
M3- stimulatory
M4- inhibitory
M5- stimulatory

Question 21

Overall is there a higher conc of M2 inhibitory receptors or M3 stimulatory receptors?

Answer 21

M3

Question 22

Sympathetic dominance occurs through having high conc of what receptors and where specifically (during receptor activity filling & storage phase)

Answer 22

b2 receptors in Detrusor (causing relaxation)
a1 receptors in internal sphincter (causing contraction)

Question 23

During Receptor activity during voiding/micturition, which 2 receptors are especially active by parasympathetic stimulation and where

Answer 23

Stimulatory receptors M3 in wall of bladder (causing contraction)

Inhibitory receptors M2 at internal sphincter (cause relaxation of sphincter)
More M2 found at level of presynaptic fibres so inhibit sympathetic NS

Question 24

2 disorders of storage of urination

Answer 24

Urinary incontinence
Urinary retention

Question 25

Urinary incontinence disorders is caused by what 2 problems

Answer 25

Hypercontractile detrusor- too much activity in detrusor

Hypocontractile sphincter/urethra- too little activity of sphincter

Question 26

Urinary retention disorder is caused by what 2 problems

Answer 26

Hypocontractile detrusor- too little activity in detrusor

Hypercontractile Sphincter/urethra- too much activity of sphincter/urethra