Exam 3 - Lecture 40 (Regulation of K+) Flashcards
Why is K+ important in the EC space even though it is so low?
Bc it detects RMP
What is the main IC cation?
K+
What is hypokalemia?
Decreased ECF K+ levels
What is hyperkalemia?
Increased ECF K+ levels
What does K+ balance determine and why?
Behavior of all excitable cells because it is the major determinant of RMP
What happens to AP during hypokalemia?
Harder to initiate
What happens to AP during hyperkalemia?
Harder to repeat
Between hypokalemia and hyperkalemia, which is more serious?
hyperkalemia
What are the 4 symptoms of hypokalemia?
- Muscle weakness
- Respiratory problems
- Cardiac arrythmia
- Renal dysfunction (Polyuria/Polydypsia)
What are the 2 symptoms of hyperkalemia?
- Muscle weakness (e.g. cats cannot keep head up bc lack nuchal ligament)
- Cardiac dysfunction
What does insulin promote?
Movement of K+ into cells by stimulating Na+K+ATPase
What 3 things regulate external and internal balance of K+?
- Insulin
- Epinephrine
- Acidosis/Alkalosis
What does epinephrine promote?
Movement of K+ into cells AND out of cells thru adrenergic receptors
How does epinephrine promote movement of K+ into cells?
Thru beta-2 stimulation of Na+K+ATPase
How does epinephrine promote movement of K+ out of cells?
Thru alpha stimulation of Na+K+ATPase
What do alkalosis/acidosis promote?
Alkalosis = low [H+] = moves K+ into cells Acidosis = high [H+] = moves K+ out of cells
Acidosis = _____kalemic
hyper
Alkalosis = _____kalemic
hypo
Tomcats are _____kalemic when blocked because EC K+ levels build up.
hyper
___% of K+ reabs. happens in the PT.
67%
Lumen positive PD moves K+ via _____ route in the PT and DST.
paracellular
Which statement about ECF [K+] is most accurate?
A) ECF [K+] is higher than that of ICF
B) Insulin will increase ECF [K+]
C) Acidemia (decreasing ECF pH) is likely to lower ECF [K+]
D) Increased dietary K+ will decrease ECF [K+]
E) Oliguria (low urine output) may increase ECF [K+]
E) Oliguria (low urine output) may increase ECF [K+]
What is oliguria?
low urine output
___% of K+ reabs. happens in the DST.
20%
How does Cl- move in the DST?
Paracellularly AND transcellularly (by NKCC1)
Loop diuretics can cause _____.
hypokalemia
What are the 3 steps by which the CD’s principal cells regulate K+?
- Na+K+ATPase generates Na+ gradient
- Na+ enters cell via amiloride sensitive Na+ channels
- K+ leaves thru K+ channels down K+ gradient
What happens to K+ in alpha-intercalated cells?
Absorption
What 3 things determine renal K+ excretion?
- Plasma [K+]
- Tubular flow rate
- Lumen electronegativity
What happens when there is increased plasma [K+]?
More K+ enters cell, more leaves by luminal membrane and vice versa
When is aldosterone stimulated?
When ECF [K+] is elevated
What 3 things does aldosterone do when ECF K+ is elevated?
- Increases Na+K+ATPase
- Increases Na+ channels
- Increases K+ channels
What is hyperaldosteronism and what does it do/lead to in regards to K+?
Elevated aldosterone release; more K+ moves into the cell –> hypokalemia
What is hypoaldosteronism and what does it do/lead to in regards to K+?
Lowered aldosterone release; less K+ moves into the cell –> hyperkalemia
What happens to tubular flow rate of K+ during diuresis/antidiuresis?
Diuresis = ADH increases perm. of lum. mem. to K+ Antidiuresis = ADH decreases perm. of lum. mem. to K+
What is lumen electronegativity?
How negative tubular fluid is
What happens to K+ when LE is increased?
K+ secretion increases
What happens to K+ when LE is decreased?
K+ secretion decreases
What is an example of a drug that increases LE?
Penicillin
How does Na+ intake affect renal handling of K+?
If there is too much Na+ in the diet, more Na+ is reabs. so more K+ is excreted.
How does acidosis affect renal handling of K+?
It makes the basolateral mem. more permeable to K+, so K+ leaves at BLM and secretion is inhibited.
How does alkalosis affect renal handling of K+?
It makes the BLM less permeable to K+, so K+ does not leave and is excreted.
How do loop diuretics affect renal handling of K+?
Cause hypokalemia so promote K+ secretion
How do amiloride-like diuretics affect renal handling of K+?
Inhibit Na+ channel on lum. mem., less K+ is excreted but does not result in hypokalemia
Which of the following could lead to hypokalemia?
A) Increased aldosterone secretion
B) Amiloride-like diuretics
C) Decreased lumen electronegativity
D) Low tubular flow rate
A) Increased aldosterone secretion
Bartter’s syndrome is a genetic disroder that causes a dysfunctional, impaired NKCC1. What can be a result?
A) Hypokalemia
B) Hyperkalemia
A) Hypokalemia
