Cardiovascular system- DIURETICS Chapter 41 (459-466) Flashcards
3 basic renal processes
1) filtration at glomerulus
2) reabsorption (more than 99% of the water, electrolytes, and nutrients that are filtered at the glomerulus undergo reabsorption)
3) Active Tubular Secretion (pumps can promote the excretion of a wide assortment of molecules; pumps of active secretion are located in the proximal convoluted tubule)
kidneys produce 180L of filtrate/day (practically all is reabsorbed)
Proximal Convoluted Tubule; process of reabsorption
-a large fraction (65%) of filtered Na and Cl is reabsorbed at the PCT
Loop of henle; process of reabsorption
-The descending LOH is freely permeable to water, hence as tubular urine moves down the loop & passes through the hypertonic environment of the renal medulla, water is drawn from the loop into the interstitial space. this process decreases the volume of the tubular urine and causes he urine to become concentrated
-The ascending LOH- about 20% of filtered Na and Cl is reabsorbed. NOT permeable to water (water must remain in the loop as reabsorption of Na and Cl takes place). This process causes tonicity of the tubular urine to return to that of the original filtrate
Distal Convoluted Tubule (Early segment); process of reabsorption
10% of filtered Na and Cl is reabsorbed in the early segment of the DCT. water follows passively
Distal Nephron (late DCT & collecting duct); process of reabsorption
-distal nephron is the site of two important processes
1) exchange of Na for K (under influence of aldosterone
2) determines the final concentration of the urine and is regulated by ADH
How do diuretics work?
Blocking of Na and Cl reabsorption
-by blocking these solutes, diuretics create osmotic pressure within the nephron that prevents the passive reabsorption of water
-diuretics cause water and solutes to be retained within the nephron and thereby promote the excretion of both
-drugs that act early in the nephron have the opportunity to block the greatest amount of solute reabsorption
