33.3d Role of Electrolytes

electrical and mechanical

Cardiac function, both (?) , depends heavily on electrolyte balances.

sodium (Na+), calcium (Ca++), potassium (K+), chloride (Cl-), and magnesium (Mg++)

Electrolytes that affect cardiac function include (?).

Sodium

Sodium plays a major role in depolarizing the myocardium.

Calcium

(?) takes part in myocardial depolarization and myocardial contraction.

Hypercalcemia, hypocalcemia

(?) can result in increased contractility whereas (?) is associated with decreased myocardial contractility and increased electrical irritability.

Potassium

(?) influences repolarization.

Hyperkalemia, hypokalemia

(?) decreases automaticity and conduction whereas (?) increases irritability.

magnesium and chloride

New research is also investigating the roles of (?) in the cardiac cycle.