control of micturition

Question 1

what is micturition

Answer 1

the normal process of the passive storage and active voiding of urine

Question 2

how does urine move from the kidneys to the bladder

Answer 2

• movement of urine alond the ureter is by peristalsis
• locally regulated smooth muscle
• maintaining low pressure in the renal pelvis

Question 3

how is retrograde flow from the bladder prevented

Answer 3

oblique angle of entry through the bladder wall by the ureter

Question 4

the bladder is lined by which type of muscle

Answer 4

smooth muscle

Question 5

the urethra is lined by which types of muscle

Answer 5

smooth and skeletal muscle

Question 6

what is the detrusor muscle

Answer 6

• network of smooth muscle fibres within the bladder wall
• supplied by both sympathetic and parasympathetic fibred

Question 7

what is the internal urethral sphincter

Answer 7

• thickening of the bladder musculature
• smooth muscle
• supplied by sympathetic supply

Question 8

what is the external urethral sphincter

Answer 8

• striated muscle fibres
• under voluntary control of somatic nervous system

Question 9

what is the innervation involved in the bladder and urethra

Answer 9

• sensory stretch nerve endings in the bladder wall
• motor supply to detrusor, internal and external urethral sphincters

Question 10

innervation involved in micturitiin:

Answer 10

motor:
- somatic
- parasympathetic
- sympathetic

sensory

Question 11

somatic motor supply to the bladder is via: and functions to

Answer 11

• outflow of S1-2 - pudendal nerve
• no synpase
• innervates the external urethral sphincter
• functions to retain urine

Question 12

parasympathetic supply to the bladder is via ……… and functions to…..

Answer 12

• outflow: S1-3 - pelvic plexus
• synpases at pelvic plexus or bladder wall
• innervates the detrusor muscle
• neurotransmitter = ACh
• action = excitatory = squeeze bladder for peepee
• function = to empty bladder

Question 13

the sympathetic supply to the detrusor muscle is via ………. and functions to:

Answer 13

• outflow = L1-4
• synapses at the caudal mesenteric ganglion (or bladder wall)
• innervates the detrusor muscle
• neurotransmitter = norepinephrine
• receptor = beta
• action = inhibitory
• function is to allow the bladder to fill (dont pee pants)

Question 14

sympathetic supply to the internal sphincter is via ……. and functions to:

Answer 14

• outflow L1-4
• synpases at caudal mesenteric ganglion
• innervats the internal sphincter
• neurotransmitter - norepinephrine
• receptor = alpha
• action = excitatory
• function is to retain urine and increase urethral tone

Question 15

sympathetic tone to the bladder will
a. retain urine
b. void urine

Answer 15

retain

Question 16

what are the central connections for nervous supply to the bladder

Answer 16

control at the level of the pons and cerebral cortex with some postulated control at the cerebellum.
sympathetic from pons, somatic from cerebral cortex

Question 17

what is the detrusor reflex

Answer 17

• increased vesicular pressure with filling achieves threshold resulting in contraction of the detrusor muscle
• contraction occurs against urethral sphincter tone

Question 18

what is the micturition reflex

Answer 18

• a combination of detrusor reflex with inhibition of sympathetic and voluntary motor supply to the bladder and urethra

Question 19

what type of feedback is the detrusor reflex

Answer 19

positive feedback
- once started usually continued until bladder is emptied

Question 20

how is urination controlled

Answer 20

• suppression of autonomic reflexes
• never complete, once overfilled the intact bladder will empty automatically regardless of signal from animal

Question 21

how is voluntary urination initiated

Answer 21

increased intra-abdominal pressure and voluntary release of urinary sphincter

Question 22

what are the effects of drugs on micturition

Answer 22

• alpha adrenergic blockers such as phenoxybenzamine decrease sphincter tone
• alpha sympathomimetic drugs such as phenylpropanolamine increase sphincter tone
• skeletal muscle relaxants decrease sphincter tone
• parasympathomimetic drugs such as bethanecol increase detrusor tone