Potassium (K\(^+\))

Used in cellular sodium-potassium pumps initiate an action potential.

Potassium is absorbed within the GI tract. Insulin moves K\(^+\) into cells, while aldosterone increases blood volume by moving K\(^+\) into the renal tubule (i.e. excreting it in urine) to reabsorb Na\(^+\) into the ECF.

Hyperkalemia

1. Too much serum K\(^+\).
2. K\(^+\) does not osmose out of the cell.
3. Cell cannot repolarize after an action potential.
4. Muscles become "floppy"— lose tone and cannot contract.

The primary symptom of hyperkalemia is muscle weakness.

Hypokalemia

1. Not enough serum K\(^+\).
2. No K\(^+\) to pump into cells.
3. Cell cannot depolarize to start an action potential.
4. Muscles become "floppy"— lose tone and cannot contract.

The primary symptom of hypokalemia is muscle weakness.