L24 - Renal Function 3: Tubular Function & Electrolyte Balance Flashcards
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)?
300 ml/min
Which tubular activity is bigger? (reabsorption / secretion / neither)
reabsorption
Where is reabsorption greatest along the nephron?
proximal tubule
What is the most important solute to be reabsorbed?
sodium
Why is sodium the most important solute to be reabsorbed?
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
Into which structures do compounds enter upon reabsorption?
peritubular capillaries
Which solutes are actively reabsorbed?
amino acids, glucose, sodium, lactate
How is SGLT protein used?
Na+ moving down its electrochemical (EC) gradient uses the SGLT protein to pull glucose into the cell against its concentration gradient
What are secondary active transporters used for in the proximal tubule cell?
transporting compounds along with Na+ across the luminal membrane
What are facilitated diffusion carriers used for in the proximal tubule cell?
allowing for reabsorption of compounds across the basolateral membrane into the interstitial fluid (glucose uses GLUT protein)
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)
none of the above
Why does glucose appear in the diabetic’s urine?
diabetics have such high levels of glucose in the blood that it reaches above renal threshold of glucose plasma concentration 4 mg/mL
What is 80% of oxygen consumed by the kidney tied to?
reabsorption of water, chloride, glucose, amino acids and urea and secretion of potassium, hydrogen ions
What are the effects of aldosterone in the collecting duct?
↑ activity of sodium / potassium pump
↑ expression of ENaCs on luminal membrane
↑ potassium secretion
↑ activity of hydrogen ATPase on luminal membrane
What are the overall effects of aldosterone in the collecting duct?
↑ Na+ reabsorption and ↑ K+, H+ secretion
What are the primary characteristics of hyperaldosteronism?
hypokalemic, alkalotic and high MAP
What is the input and output of sodium per day?
input: diet (food and drink) = 150 mmol
output: urine = 140 mmol
faeces = 8 mmol
skin = 2 mmol
What happens during a positive sodium balance? What happens once sodium balance becomes negative?
increased weight as a result of water retention
weight decreases as water is removed from the body during urination
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)
0.25 L because about a quarter of blood volume is consisted of plasma
The body detect sodium balance through the use of…
carotid baroreceptors, renal arterial pressure receptors and cardiac atrial baroreceptors
Sodium excretion can be altered by which of the following? (renin-angiotensin system / sympathetic nervous system / atrial natriuretic peptide / vasopressin)
renin-angiotensin system, sympathetic nervous system and atrial natriuretic peptide
