Renal sodium and water regulation

Question 1

What role does renal sodium and water regulation play within the body?

Answer 1

Role in regulating blood pressure

Question 2

How is water excretion separated from water excretion?

Answer 2

Osmoreceptors and ADH-dependent water reasborption in collecting duct

Question 3

How should Na+ and H2O intakes relate to output?

Answer 3

Should be equal; often determined by diet and exercise

Question 4

Where is Na+ reabsorbed?

Answer 4

PCT, ascending limb of Loop of Henle, DCT

Question 5

How is Na+ reabsorbed?

Answer 5

Na+ through Na+/K+ ATPase pump on basolateral membrane; Na+ actively into interstitial fluid from epithelial cells; intracellular Na+ decreases below tubular lumen; Na+ into epithelial cell from tubular lumen: in PCT, by cotransport/counter-transport of organic molecules; in loop of Henle, by Na+ channels

Question 6

How is H2O reabsorbed coupled with Na+ reabsorption?

Answer 6

Na+ into epithelial cell; local osmolarity within tubular lumen decreased; H2O into epithelial cell then interstitial fluid

Question 7

How do aquaporins increase water reabsorption?

Answer 7

ADH binds to receptors; G protein activated; adenylate cyclase activated; cAMP released; increased activity of protein kinase A (PKA); increases phosphorylation of proteins that increase rate of fusion of vesicles containing APQ2 with luminal membrane; water into cell through APQ2; water out of cell by APQ3 and 4

Question 8

What is ADH regulated by?

Answer 8

Osmoreceptors and baroreceptors regulate release from posterior pituitary gland

Question 9

How do osmoreceptors control ADH secretion?

Answer 9

Excess H2O decreases blood fluid osmolarity; hypothalamic osmoreceptors decrease firing; ADH secretion decreased

Question 10

How do baroreceptors control ADH secretion?

Answer 10

Reduced H2O decreases plasma volume; vascular pressure decreased; CV baroreceptors decrease firing; increases ADH secretion

Question 11

What determines Na+ excretion?

Answer 11

Aldosterones, atrial natruretic peptide (ANP), local effect of blood pressure on the tubules

Question 12

How do aldosterones control Na+ excretion?

Answer 12

Induces synthesis of channel and pumps that participate in Na+ transport; regulates via regulation of K+: increased K+ increases aldosterone secretion from adrenal cortex, which increases K+ excretion

Question 13

How does ANP control Na+ excretion?

Answer 13

Increased plasma volume increases atria distension; ANP secretion increased; decreases aldosterone, and dilates afferent arteriole and contracts efferent arteriole; GFR increased; decreased Na+ reabsorbed; Na+ excretion decreased

Question 14

How does local blood pressure control Na+ excretion?

Answer 14

High pressure inhibits Na+ reabsorption and reduces rennin release

Question 15

What is GFR affected by?

Answer 15

Volume of surface availability; permeability of filtration membrane; net filtration pressure; blood pressure/flow to glomerular capillaries

Question 16

How is thirst controlled?

Answer 16

Baroreceptors decrease firing with decreased pressure = angiotensin II increased = thirst increased. Plasma omolarity decreased = osmoreceptors increase firing = increased thirst. Dry mouth/throat = increased thirst. Metering of water intake by GI tract = decreased thirst

Question 17

What are diuretics?

Answer 17

Substances that promote the loss of Na+ and H2O

Question 18

What are different diuretics?

Answer 18

Alcohol, osmotic diuretics, loop diuretics, hydrochlorothiazide, sprinonolactone

Question 19

How does alcohol act as a diuretic?

Answer 19

Inhibits ADH

Question 20

What do osmotic diuretics do?

Answer 20

Are carbs that are filtered but not reabsorbed = exert osmotic effect and keep H2O in tubular lumen

Question 21

What do loop diuretics do?

Answer 21

Inhibit Na+ reabsorption in loop of Henle = water does not diffuse out

Question 22

What does hydrochlorothiazide do?

Answer 22

Acts on collecting duct

Question 23

What does spironolactone do?

Answer 23

Is an aldosterone receptors antagonist = K+ stays in tubular lumen = H2O stays in tubular lumen