Electrochemical Impulses

Introduction:

Electrochemical impulses also called nerve impulses or action potential are conducted by specialized cells called neurons. All neurons conduct impulses along hair like cytoplasmic extensions, the nerve fibers or axons outside the central nervous system. A short-lasting event, in which the electrical membrane potential of a cell rises rapidly and falls, is known as an action potential.

In several types of animal cells, action potential occurs. These cells are called excitable cells which include neurons, muscle cells, and endocrine cells.

Function of Electrochemical Impulses:

In neurons, cell-to-cell communication is the major role of action potential. In other types of cells, activation of intracellular processes is their major function.

Mechanism of Electrochemical Impulses:

An action potential is the first step in the chain of events leading to contraction in muscle cells. They provoke release of insulin in beta cells of the pancreas. Special types of voltage gated ion-channels embedded in a cell's plasma membrane are responsible for generation of Action potential. When the membrane potential is near the resting potential of the cell, these channels are shut but they rapidly begin to open if the membrane potential increases to a precisely defined threshold value.

When the channels open, an inward flow of sodium ions is allowed, which changes the electrochemical gradient, which in turn produces a further rise in the membrane potential. This causes more channels to open, producing a greater electrical current. Until the entire ion channels are open, the process proceeds explosively leading to a large upswing in the membrane potential. The polarity of the plasma membrane gets reversed and the ion channels then rapidly inactivate because of the rapid influx of sodium ions.

As the sodium channels closes, it does not allow entry of sodium ions and they are actively transported out the plasma membrane. There is an outward current of potassium ions as potassium channels channels are activated, which returns the electrochemical gradient to the resting state.