L24 - Renal Function 3: Tubular Function & Electrolyte Balance

Question 1

If inulin has a plasma concentration of 4mg/100mL, and inulin appears in the urine at 12mg/min, what is the clearance rate of inulin (in ml/min)?

Answer 1

300 ml/min

Question 2

Which tubular activity is bigger? (reabsorption / secretion / neither)

Answer 2

reabsorption

Question 3

Where is reabsorption greatest along the nephron?

Answer 3

proximal tubule

Question 4

What is the most important solute to be reabsorbed?

Answer 4

sodium

Question 5

Why is sodium the most important solute to be reabsorbed?

Answer 5

activity of Na+-K+ pump results in active transport of Na+ from tubular epithelium into ECF -> EC gradient drives anion reabsorption -> water follows via osmosis -> as water ↓ in lumen, [other solutes] ↑ and permeable solutes are reabsorbed by diffusion

Question 6

Into which structures do compounds enter upon reabsorption?

Answer 6

peritubular capillaries

Question 7

Which solutes are actively reabsorbed?

Answer 7

amino acids, glucose, sodium, lactate

Question 8

How is SGLT protein used?

Answer 8

Na+ moving down its electrochemical (EC) gradient uses the SGLT protein to pull glucose into the cell against its concentration gradient

Question 9

What are secondary active transporters used for in the proximal tubule cell?

Answer 9

transporting compounds along with Na+ across the luminal membrane

Question 10

What are facilitated diffusion carriers used for in the proximal tubule cell?

Answer 10

allowing for reabsorption of compounds across the basolateral membrane into the interstitial fluid (glucose uses GLUT protein)

Question 11

Glucose appears in the diabetic’s urine because diabetes? (reduces Na/K ATPase activity / reduces Na/glucose cotransport / reduces GLUT activity / none of the above)

Answer 11

none of the above

Question 12

Why does glucose appear in the diabetic’s urine?

Answer 12

diabetics have such high levels of glucose in the blood that it reaches above renal threshold of glucose plasma concentration 4 mg/mL

Question 13

What is 80% of oxygen consumed by the kidney tied to?

Answer 13

reabsorption of water, chloride, glucose, amino acids and urea and secretion of potassium, hydrogen ions

Question 14

What are the effects of aldosterone in the collecting duct?

Answer 14

↑ activity of sodium / potassium pump
↑ expression of ENaCs on luminal membrane
↑ potassium secretion
↑ activity of hydrogen ATPase on luminal membrane

Question 15

What are the overall effects of aldosterone in the collecting duct?

Answer 15

↑ Na+ reabsorption and ↑ K+, H+ secretion

Question 16

What are the primary characteristics of hyperaldosteronism?

Answer 16

hypokalemic, alkalotic and high MAP

Question 17

What is the input and output of sodium per day?

Answer 17

input: diet (food and drink) = 150 mmol
output: urine = 140 mmol
faeces = 8 mmol
skin = 2 mmol

Question 18

What happens during a positive sodium balance? What happens once sodium balance becomes negative?

Answer 18

increased weight as a result of water retention

weight decreases as water is removed from the body during urination

Question 19

Infusion of 1 L of normal saline will cause a change in blood volume of: (1 L / 0.5 L / 0.25 L / 0.1 L / <0.1 L)

Answer 19

0.25 L because about a quarter of blood volume is consisted of plasma

Question 20

The body detect sodium balance through the use of…

Answer 20

carotid baroreceptors, renal arterial pressure receptors and cardiac atrial baroreceptors

Question 21

Sodium excretion can be altered by which of the following? (renin-angiotensin system / sympathetic nervous system / atrial natriuretic peptide / vasopressin)

Answer 21

renin-angiotensin system, sympathetic nervous system and atrial natriuretic peptide