Micturition

Question 1

What is the sympathetic input to the bladder?

Answer 1

Preganglionic fibres - splanchnic nerve

Postganglionic fibres - hypogastric nerve to detrusor muscle and internal sphincter

Question 2

What is the parasympathetic input to the bladder?

Answer 2

Preganglionic fibres - pelvic nerve to pelvic plexus in detrusor

Question 3

What is the somatic nervous input to the bladder?

Answer 3

Pudenal nerve to external sphincter

Question 4

Describe what happens during filling of the bladder

Answer 4

1. Internal sphincter:
   - bladder stretches causing tension to be passively exerted on by elastic elements in neck of bladder
   - sphincter closes
   - sympathetic stimulation, sm muscle contracts, sphincter closes
2. External sphincter
   - somatic stimulation, pudenal nerve causes contraction of urethralis muscle in external sphincter
   - sphincter closes

Question 5

Describe what happens during storage of urine

Answer 5

1. Parasympathetic - downregulated
   - distension of bladder wall registered by afferent fibres that run out to level of S1-S3
   low stimulation causes inhibition of activity of efferent fibres
   - detrusor relaxes, expands
2. Sympathetic - upregulated
   - excitation of hypgastric nerve
   - relaxation of detrusor
   - activity runs to external sphincter causing contraction

Question 6

Describe what happens during micturition

Answer 6

1. Parasympathetic - upregulated
   - increased stimulation of afferent nerve, increases activity and intensity of transmission
   - reaches critical level, stimulates efferent fibres
   - detrusor muscle contracts
2. Sympathetic - downregulated
   - hypogastric nerve inhibited
   - detrusor contracts
   - internal sphincter relaxes and opens
3. Somatic
   - pudenal nerve inhibited
   - urethralis muscle relaxes
   - external sphincter opens

Question 7

How is micturition under voluntary control?

Answer 7

Sensory cortex can inhibit parasympathetic action if is not appropriate time to pee.

Question 8

What can an animal experience during abnormal micturition?

Answer 8

Urinary retention, urinary incontinence.

Question 9

What is meant by urinary retention and what causes it?

Answer 9

Incomplete emptying/voiding of urine with no obstruction to the urinary tract.
Trauma to pelvic/spinal nerve, spinal disease, slipped disc, chronic bladder distension, electrolyte disturbance, excessive adrenal steroids (Cushings)

Question 10

What can cause urinary incontinence?

Answer 10

Spay, old age, diabetes, kidney disease, nerve damage/trauma, UTIs