Sports drinks fortified with potassium are fixtures in locker room coolers at athletic events. That’s because potassium is vital to muscle function. Along with sodium and calcium, potassium helps enable muscle contraction, whether the contraction involves voluntary muscles you control in everyday activity, the involuntary muscles that allow your intestines to push digestive material to excretion, or the cardiac muscle that allows your heart to continue pumping.
Potassium
Potassium is an essential mineral, which means that your body requires it but cannot make it on its own. It is also an electrolyte, which means it forms a charged particle, called an ion, in solution. Because your body is largely composed of water, the potassium in your body is found in its ionic form. The concentration of potassium ions inside the cells of your body is about 30 times higher than the concentration in the fluids surrounding those cells. This concentration disparity creates an electrochemical gradient, called membrane potential, which is crucial in helping muscles contract and nerve cells to transmit impulses.
Resting Membrane Potential
In addition to the differences in potassium concentration between the inside and outside of your cells, sodium concentrations also vary across cell membranes. The concentration of sodium outside the cell is about 10 times higher than the sodium concentration inside your cell. Together, the sodium and potassium concentrations form the resting membrane potential, which is the electrochemical difference between the inner cell and the fluid surrounding it when a muscle cell is at rest. Pumps in your cell membranes ensure these concentrations are maintained until an excitation signal causes the depolarization needed to cause a muscle contraction.
Contraction
A muscle contraction begins when proteins in the cell membrane change configuration, allowing sodium ions to flow into the cell, depolarizing the electrochemical gradient. This depolarization signals the release of calcium which then results in muscle contraction. Prompted by the change in sodium concentration, potassium responds by flowing out of the cell, re-establishing the resting membrane potential.
Considerations
Although potassium is vital to muscle contraction, do not take potassium supplement without a doctor’s supervision. Abnormal increases in potassium intake can result in hyperkalemia, or high blood potassium levels, which can cause muscle weakness, paralysis, cardiac arrhythmias and heart attack. A safer method of increasing potassium intake is to enrich your diet with foods like fruits, vegetables and nuts. According to the Linus Pauling Institute, the potassium normally found in foods has never been associated with adverse effects in healthy individuals.
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