2. DSA Intro to Regulation of K, Ca, P, Mg Balance Flashcards
What is the normal plasma concentration of K+?
3.5-5.0mEq/L
98% of K is intracellular while 2% is extracellular, this 30fold difference is due to the NaKATPase and NKCC2 transporters. How is the ICF K+ divided and what is the input and out put?
ICF divided into muscle cells =80% and 20% other cells
intake of K equals output of K+ via 10% stool and 90% urine
What occurs when plasma K concentration is below 3.5, commonly caused by vomitting/diarrhea, insulin excess, and dietary deficiency?
hypokalemia
What occurs when K+ [plasma] is about 5.0, commonly caused by excessive dietary intake of K+, tissue release, and shifts from ICF to ECF?
Hyperkalemia
What is pseudohyperkalemia?
artificially high plasma K due to lysis of RBCs while blood is drawn
A majority of K+ is stored in muscle, liver, bone, and RBCs. The majority is lost via?
feces (10mmol/day) and urine (60mmol/day)
Regarding skeletal muscle, hypokalemia hyperpolarizes the membrane resting potential, making it more negative and less likely to start an AP. How about hyperkalemia?
Hyperkalemia raises the resting membrane potential to be less negative, making it easier to start and AP/ muscle contraction
The cardiac conduction system responds in the opposite direction compared to skeletal muscle. So hyperkalemia makes the RMP hyperpolarized, meaning it would be harder to start an AP. What would hypokalemia do?
would make it easier to activate an AP, leading to tachycardia
Low T-wave in hypokalemia and what is seen in hyperkalemia?
a high peaked T wave
Hyperosmolality, alkalosis, B-catecholamines, and insulin all do what to K+ cell uptake?
INCREASE/ENHANCE
A-catecholamines, acidosis, and cell damage all do what to K+ cell uptake?
DECREASE/IMPAIR
What does external potassium balance do to K+?
loose correlation
What is the normal range of dietary Ca2+ intake?
1000mg/day for adults
Calcium is absorbed via the GI tract, renal tubular reabsorption via calcitriol and PTH, internally redistributed in bone, and how is Ca2+ lost?
through stool and urine, 80/20%
all intake will be output
Hypocalcemia increases neuromuscular excitability (d/t shorter contraction?) while hypercalcemia decreases nueromuscular excitability. This is regulated via what 3 things?
PTH, Calcitonin, Calcitriol
Primary hyperparathyroidism and malignancy would lead to what?
elevated serum calcium
Low serum calcium would lead to what three things?
hypothyroidism
renal disease
Vit D deficiency
What is the normal range of dietary Phosphate?
1500mg/day
85% of phophate is stored in the bones, while 14% is stored in cells and 1% in serum. It is lost via?
lost via stool and urine, more in urine, equal input to output
The four main regulators of phosphate metabolism are dietary, calcitriol, PTH, and renal tubular. How is dietary one?
via phosphate intake and absorption
How does calcitriol regulate phosphate metab?
increases phosphorus resorption from bone and absorption from intestine
How does PTH regulate phosphate metab?
phosphorus resorption directly from bone, indirectly activates instestinal absorption through stimulation of calcitriol production
how does renal tubular reabsorption regulate phosphate metab?
by reabsorption stimulated by tubular filtered load of phosphorus and inhibited by PTH
Magnesium (mg) is almost in every biochemical process in the cell. When depleted it is associated with migraine, depression epilepsy SIDS, and muscle cramps. Where is it stored and how is it excreted?
50% stored in bone, 49% stored in ICF in muscle 1%ECF
intake = output, more via feces
Total serum mg is 1.8-2.2 while free serum mg is 0.8-1.0. What is the difference between these?
free serum is unbound while total serum is ionized, diffusible and protein-bound mg.
