Potassium is a chemical element and it is part of the electrolyte that should be in balance with other lytes to adequately conduct an electrical impulse that originates with the sinus node in the right atrium. The mechanism of action is not completely understood, but what is when a voltage (unit of potential for conduction) and electrolyte there will conduction and passage of electrical impluses. When the polar opposites cathode (negative electrons) and anode (positive electrons) reach a specific level there will be repolarization by transfering electrons from anode to the cathode. This action with subsequent repolarization of cells move the electrical impulse along a path to a destination to contract heart chambers. If there is an electrolytic imbalance (chemical dissociation), that can cause an arrythmia (fast, slow or irregular).
"In physiology, the primary ions of electrolytes are sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), chloride (Cl−), hydrogen phosphate (HPO42−), and hydrogen carbonate (HCO3−). The electric charge symbols of plus (+) and minus (−) indicate that the substance in question is ionic in nature and has an imbalanced distribution of electrons, the result of chemical dissociation". There are various mechanism to keep the different concentrations of different electrolytes under close control.
Hypokalemia is usually caused by the body losing too much potassium in the urine or intestines; it's rarely caused by a lack of potassium in the diet. Hypokalemia can be life-threatening and should always be treated by a doctor. Connection with blood pressure is not conclusive but there is some evidence it may lower blood pressure.
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Ken