Unit 4: Renal Phys.-- Sodium and Potassium Balance Flashcards
What is the most important function of the kidney? Why?
reabsorption of Na+ b/c all reabsorption is tied to it and it helps regulate BP
What is responsible for maintaining a normal Na+ concentration in the body?
the kidneys
What does it mean if there is a positive Na+ balance?
What if there is a negative Na+ balance?
positive–> excretion is less than intake and accumulate Na+
negative–> excretion is greater than intake–> will be deficient in Na+
When we have a positive Na+ balance, where does the excess Na+ primarily accumulate? What does this lead to?
in ECF–> leads to ECF volume expansion –> which will increase BV and BP
may be assoc. with edema
When we have a negative Na+ balance, where is excess Na+ primarily lost from? What does this lead to?
primarily from ECF–> leads to ECF volume contraction –> decreases BV and BP
Where is the majority of our body K+?
ICF - 98%
ECF- 2%
What type of effect will a small shift of K+ into or out of our cells have?
cause a large change in K+ conc. in ECF
shifts always have a greater impact on K+ ECF conc.
How is the large differential of K+ in ICF and in ECF maintained?
via the Na+-K+ ATPase pump
3 Na+ out
2 K+ in
What is the major cation taht exchanges for H+?
K+
What may cause a shift of K+ from ICF –> ECF?
- insulin deficiency
- beta2-adrenergic antagonists
- alpha-adrenergic agonists
- acidosis
- hyperosmolarity in ECF
- cell lysis
- exercise
What may cause a shift of K+ from ECF –> ICF?
- insulin
- beta2-adrenergic agonists (NE)
- alpha-adrenergic antagonists (Beta blocker)
- alkalosis
- hyposmolarity
What effect does insulin have on the Na+K+ pump? Why is this important?
increases activity of it –> helps move ingested K+ into cells after a meal
prevents hyperkalemia after K+ rich meal
What will high levels of insulin cause involving K+? What would type I diabetes cause?
high levels of insulin–> hypokalemia ( less than 2 mEq/L)
type I diabetes–> hyperkalemia (more than 5 mEq/L
(normal levels are ~4.5 mEq/L)
What are acid-base abnormalities often associated with?
K+ abnormalities
What is the term for low H+ conc. in the blood? What will the cause to happen?
Alkalemia
will cause:
- H+ (from cells)–> to ECF
- K+ from ECF –> into cells, ICF (creates hypokalemia)
What is the term for high H+ conc. in the blood? What will this cause to happen?
Acidemia
- H+ (from blood)–> into ICF
- K+ from cells –> into ECF (creates hyperkalemia)
K+ disturbances only occur in certain metabolic acidosis or alkalosis. What may these cases be?
- effect HCO3- and H+
- excess of organic acid (lactic acid, ketoacids, salicylic acid)
- –they will enter cell in exchange for H+ and no need for K+ exchange
In what acid-base abnormalities do K+ disturbances not occur?
respiratory acidosis or alkalosis
–> these are due to change in CO2 which is lipid soluble and diffuse across membrane w/o effecting K+ ( no need to move K+ to maintain electrical neutrality)
What will activation of beta2 adrenergic receptors have on the Na+K+ ATPase?
- What do Beta2 agonists cause?
- What do Beta2 antagonists cause?
increase activity of it (pump more K+ into cell)
- hypokalemia
- hyperkalemia
What will activation of alpha- adrenergic receptors have on K+?
- What do alpha-agonist cause?
- What do alpha antagonists cause?
shift K+ out of cells
- hyperkalemia
- hypokalemia
What will an increase is osmolarity in ECF cause K+ to do?
K+ to move out of cells (b/c water will flow out and increase K+ conc. in cell and therefore want to drag K+ out of cell too
What effect will cell lysis have on K+? What are examples of what may cause this?
will dump K+ into ECF–> cause hyperkelemia
Ex: burn, rhabdomyolysis, chemotherapy, fresh water drowing**
What impact will fresh water drowning have on our cells?
cause them to burst–> release K+ into ECF (due to take on water from lungs and now water wants to rush into cells and they burst)
How does K+ shift during exercise? What impact will this have on blood vessels?
K+ shifts out of cells due to depletion of cellular ATP stores that will open K+ channels
K+ shift out of cells acts as local vasodilator helping to increase blood flow to exercising muscle
How is the External K+ balance kept in check?
kidneys play a role
output = intake
How much of K+ is filtered? Why?
K+ is FREELY filtered at glomerular capillaries due to NOT being bound to anything
filtered load of K+ = GFR x plasma conc. of K+
Where does most of the reabsorption of K+ take place? How much is it?
Where else is K+ reabsorbed? via what?
Where is the final adjustment of K+ secretion made?
In Proximal Convoluted Tubule–> 67%
Thick ascending limb–> 20% (via Na+-K+-2Cl- cotransporter)
Distal Tubule and Collecting duct (in response to dietary change)
What cells are responsible for reabsorption of K+?
alpha-intercalated cells in collecting ducts (less common) via luminal H+-K+ ATPase
What cells are responsible for secretion of K+? What may this be due to?
principle cells (more common)
- use Na+K+ ATPase on Basolateral side to pump for K+ in and…
- then passive diffusion occurs on luminal side to secrete K+
Due to:
- increase dietary K+
- increase Aldosterone
What effect will an increase in Aldosterone have on K+ secretion and how?
secrete it for by principle cells by:
- increase quantity of Na+ and K+ channels on luminal side
- increase quantity of Na+ K+ ATPase on basolateral side
What ion has the greatest variability with excretion?
K+
What effect will Alkalosis have of K+ secretion?
increase K+ secretion–> lead to hypokalemia
(a decrease in H+ ECF conc. –> causes H+ to leave vells and K+ to enter cell–> increasing driving force for K+ secretion)
What effect will Acidosis have on K+ secretion?
decreases K+ secretion–> lead to hyperkalemia
increase in H+ ECF conc.–> causes H+ to enter cell and K+ to leave cell–> decreasing driving force for K+ secretion
How will Diuretics–Lopp diuretics and thiazide diuretics–effect K+ secretion?
What will the loop diuretics also do?
will increase K+ excretion –> leading to hypokalemia
loop diuretics will also inhibit Na+K+2Cl- costransporter
cause kaliuresis and hypokalemia
What effect will K+ sparing Diuretics have on K+ secretion?
inhibit action of aldosterone (which + secretion of K+) on principle cells –> therefore inhibit K+ secretion
(do not cause kaliuresis and hypokalemia)
How will large anions in the luminal fluid (like sulface and HCO3-) effect K+ secretion?
promote K+ secretion
they are negative charged and attracted positive ions
