Physiology of the Urinary Tract-

Question 1

Urinary tract has 3 anatomical divisions

Answer 1

Upper urinary tract: calyces, pelvis, ureters

Bladder: stores urine under low pressure, expels it under high pressure

Urethra: a conduit for carrying urine from the body. Its two sphincters control voiding

Question 2

Urinary Bladder and Sphincters

Answer 2

Internal (Involuntary)- smooth muscle. It is the wall of the bladder as it narrows toward the urethra

External (Voluntary)- Skeletal
muscle which wraps around exterior of urethra where it joins bladder

Question 3

Afferent pathways

Answer 3

conscious bladder sensations

Question 4

Reflex Arc

Answer 4

for the Micturition Reflex- Sacral Micturition Center

Question 5

Efferent Nervous Controls of the Bladder and Urethra

Answer 5

Sensory fibers from bladder wall, posterior urethra are activated by stretch

Parasympathetic fibers from sacral micturition center S2-S4 (pelvic nerve) stimulate detrusor muscle, inhibits contraction of internal urethral sphincter

Sympathetic fibers (hypogastric nerve) inhibits detrusor constriction, constricts internal urethral sphincter

Somatic motor neurons (voluntary; pudendal nerve) constrict external urethral sphincter

Question 6

Central Control of Micturition

Answer 6

Pontine micturition center (Barrington’s Center)
Location: locus ceruleus of the pons
Descending impulses control sacral micturition center and thoracolumbar sympathetic outflow
Coordinates activity of bladder and urinary sphincters

Question 7

Autonomic modification of peristalsis

Answer 7

Ureters are supplied with parasympathetic and sympathetic fibers
Parasympathetic stimulation increases frequency of peristaltic contractions in ureter, increasing urine delivery to bladder
Sympathetic stimulation does the opposite.