Physiology of the kidney II

Question 1

How are organic substances secreted across the rpoximal tubule

Answer 1

Indirect active transport

Question 2

What is secretion in nephrons

Answer 2

Transfer for molecules from ECF into lumen of nephron

Enables the enphron to enhance excretion of substance

Question 3

Wha is diuresis

Answer 3

drugs that promote excretion of water in urine

Question 4

Why does the apical membrane need to be not permeable to water

Answer 4

Kidney may need to reabsorb solutes but not water

Question 5

How is the collecting duct made water permeable

Answer 5

Vasopressin vind to memrbane receptor
Receptor activates cAMP second messenger system
Cell inserts AQP2 water pores into apical membrane
Warer is absorbed by osmosis

Question 6

What is AQP2

Answer 6

Aquaporin 2

Question 7

What does aldosterone do in nephron

Answer 7

Target cells are principal cells found in distal nephron epithelium
Net effect is retention of Na+ and secretion of K+

Question 8

Two primary stimuli for aldosterone release

Answer 8

Low blood pressure

Increase extracellular K+ concentration

Question 9

Action of aldosterone

Answer 9

Aldosterone combines with cytoplasmic receptor
Hormone-receptor complex initiates transcription in the nucleus
Translation and protein synthesis makes new protein channels and pumps
Aldosterone-induced proteins modulate existing channels and pumps
Result is increased Na+ reabsorption and K+ secretion

Question 10

Effects of angiotensin II

Answer 10

Increases ADH secretion
Stimulates thrist
Potent vasoconstrictor
Increases sympatheti output to the heart and blood vessels
Increases proximal tubule Na+ reabsorption