physiology of Micturition- an autonomic spinal cord reflex, 23.04.1015

1

cystometogram

• Shows the approximate changes in intra vesicular pressure as the bladder fills with urine

• Pressure peaks are called micturition waves in the cystometogram and caused by the micturition reflex

3

Posterior urethra

• Internal sphincter

• External sphincter –voluntary skeletal muscle – under voluntary control

4

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Reflex and Voluntary Control of Micturition

• Bladder filling reflexively contracts the bladder

• Internal Sphincter mechanically opens

• Stretch receptors in bladder send inhibitory impulses to external sphincter

• Voluntary signals from cortex can override the reflex or allow it to take place

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Diuretics

• Diuretics are the drugs thst promote diuresis and decrease ECF volume

Loop diuretics – furosemide – lasix ethacrynic acid they inhibit Na+ - K+ - Cl – cotransporter in

the thick loop of Henle

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Aldosterone antagonists – K+ sparring diuretics , inhibits Na+ - K+ exchange and leads to natriuresis and diuresis with retention of K+

spironolactoneThiazide diuretics – inhibit Na+ - Cl-

cotransporter in the early part of distal tubule

chlorothiazide

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Carbonic anhydrase inhibitors acetazolamide –diamox inhibit Na+ H+ antiport xanthines – caffeine theophylline inhibit tubular reabsorption of Na+, also

increase GFR