Micturition Flashcards
Which of these nerves associates with parasympathetic, sympathetic or somatic NS?
-hypogastric
-pelvic
-pudendal
Hypogastric; sympathetic
Pelvic; parasympathetic
Pudendal; somatic
3 steps of urinary bladder during micturition
Prevent urine escape (during bladder filling)
Allow urine Storage (relaxation of Detrusor wall)
Allow micturition-voiding
Prevention of urine escape during bladder filling
-2 ways this is achieved
- 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
Storage phase of micturition
-Detrusor should be relaxed so there is larger vol inside bladder
-Sphincter should be contracted so no leakage occurs
Describe the process of relaxing the Detrusor during storage phase of micturition
Describe the process of contracting the sphincter during storage phase of micturition
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
Describe process of Micturition-voiding
-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
Do dogs have any control as to when they pee?
Have some Voluntary control but when bladder gets too full and they can’t hold it at more, involuntary micturition will occur
Urinary retention
-what is it
Incomplete emptying (or voiding) of urine, with no obstruction of the urinary tract,
Causes for urine retention
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)
Urinary incontinence
-definition
Involuntary loss of urine.
Causes for Urinary incontinence
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
How do we pharmacologically manipulate micturition
Via the Autonomic nervous system using receptors
Receptors associated with sympathetic NS
Receptors associated with the parasympathetic NS
Adrenoreceptors- Noradrenaline/adrenaline receptors
Acetylcholine
4 main adrenoreceptors
a1, a2, b1, b2
a1 function
-stimulated by what NS
^ IP3 and DAG
Located near internal sphincter so stimulating a1 cause closure of sphincter
-sympathetic
b2 function
-located where
-stimulated by what NS?
Increases or decreases cAMP
Located in Detrusor and causes its relaxation
-sympathetic NS
a1
a2
b1
b2
Which of these are inhibitory and which are stimulatory
A1- stimulatory
A2- inhibitory
B1- stimulatory
B2- inhibitory
2 types of parasympathetic cholinergic receptors
Nicotinic & muscarinic
Nicotinic receptors
-type of ion movement
-stimulatory or inhibitory
-3 types
-difference between the 3 types
-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!
Muscarinic receptors
-type of ion movement
-4 types
-each type stimulatory or inhibitory
-G protein coupled receptors
M1- stimulatory
M2- inhibitory
M3- stimulatory
M4- inhibitory
M5- stimulatory
Overall is there a higher conc of M2 inhibitory receptors or M3 stimulatory receptors?
M3
Sympathetic dominance occurs through having high conc of what receptors and where specifically (during receptor activity filling & storage phase)
b2 receptors in Detrusor (causing relaxation)
a1 receptors in internal sphincter (causing contraction)
During Receptor activity during voiding/micturition, which 2 receptors are especially active by parasympathetic stimulation and where
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
2 disorders of storage of urination
Urinary incontinence
Urinary retention
Urinary incontinence disorders is caused by what 2 problems
Hypercontractile detrusor- too much activity in detrusor
Hypocontractile sphincter/urethra- too little activity of sphincter
Urinary retention disorder is caused by what 2 problems
Hypocontractile detrusor- too little activity in detrusor
Hypercontractile Sphincter/urethra- too much activity of sphincter/urethra
