Ion transport Flashcards
What percentage of salt is reabsorbed in the proximal convoluted tubule?
67%
What is the ideal homeostatic concentration of K+ in the extracellular fluid?
4.2 mEq/L
Two different mechanisms cause aldosterone
secretion from the adrenal gland
Increased K+ levels
Angiotensin II
What happens to reabsorption when there is a decrease in peritubular hydrostatic pressure?
Increases reabsorption
What happens to reabsorption when there is a decrease in peritubular colloid osmotic pressure?
Decreases reabsorption
What happens to capillary oncotic pressure as you move from the affarent to efferent arteriole?
Oncotic pressure increases
Will a urinary tract infection cause an increase or decrease in net filtration?
increased hydrostatic pressure in the tubule, decreased net filtration
Will low albumin cause an increase or decrease in net filtration?
decreased capillary osmotic pressure, increased net filtration
What four things can cause K+ to shift into cells?
- B-agonists
- Insulin
- Aldosterone
- Alkalosis
What three things can cause K+ to shift out of cell?
- Hyperosmolarity (cell shrinks)
- Exercise
- Cell lysis
What is the average fractional excretion of K+?
10-20%
Physiological factors affecting potassium secretion?
- Intracellular K+
2. Aldosterone
Two different mechanisms that cause aldosterone secretion from the adrenal gland
- Increased extracellular K+
2. Renin –> Angiotensin II
K+ losing diuretics
Furosemide
Thiazide
K+ sparing diuretics
Amiloride
Furosemide
Increased flow, increased NaCl excretion, increased K+ excretion. Na+, K+, Cl- are blocked from from leaving concentrate, so it increases flow and Na+ conc. Then, Na+ will leave nephron and K+ will enter and be excreted
Amiloride
K+ sparing, blocks Na+ conductance so it keeps K+ in the bloodstream so it is not excreted.
Most Cl- enters the cell actively or passively?
Passively! Na+ moves in and draws water with it. So Cl- concentration becomes greater and it forms a gradient so that it can flow passively.
Routes by which molecules pass in and out of tubule
Paracellular (between cells)
Transcellular (through cells)
Where are Na+/K+/Cl- transported together? Also the site of action of the ferosimide diuretics.
Thick ascending loop of Henle
Where is Na+ transported with Glu, AA? Also the location in which H+ moves out of the cell with Na+ moving in.
Proximal tubule
Where are Na+ and Cl- transported together? Also the site of action of the thiazide diuretics.
Distal convoluted tubule
Where does net sodium reabsorption occur?
In the thick ascending limb of the loop of Henle
Does chloride tend to go through cells or between cells?
Between cells due to the passive gradient that is built up
How does insulin drive K+ into cells?
Indirectly by stimulating the Na+/H+ antiporter. So, Na+ moves into cell, which activates the Na+/K+ ATPase pump.
In the late distal tubule, what is secreted by principal cells in order to increase its concentration in the urine?
K+
This system keeps plasma K+ levels in check with increasing dietary K+ intake
Aldosterone system
Symptoms of Bartter’s syndrome (mutation of Na+/K+/Cl- transporter in thick ascending limb)
Low K+ (K+ losing) Alkalosis Polydipsia Polyuria Normal to low BP
Symptoms of Gitelman’s syndrome (mutation of Na/Cl transporter in distal tubule)
Low K+ Alkalosis Polydipsia Polyurea Normal to low BP
Symptoms of Liddle’s syndrome (increased principal sodium channels open)
Low K+
Alkalosis
Hypertension
Where does net reabsorption of Na+ occur in the tubule?
In the thick ascending limb of the loop of Henle via the Na/K/2Cl co-transporter
