"The first step of an action potential involves a large concentration of passing through the cell membrane."

Sodium

Explanation:

An action potential is a wave of electrical discharge that travels along the cell membrane modifying its electrical charge distribution. Action potentials are used in the body to carry information between tissues, making them an essential feature for life.

They can be generated by various types of body cells, but the most active in their use are the cells of the nervous system to send messages between nerve cells (synapses) or from nerve cells to other body tissues, such as muscle or glands. There is always a potential difference or membrane potential between the inner and outer part of the cell membrane (usually ~70 mV). The charge of an active cell membrane remains negative (inside vs. outside) and varies within narrow images.

The difference in membrane potential is due to the differential distribution of ions (mostly chlorine and sodium on the outside of the cell, and potassium and organic anions on the inside). The cause of the action potential is the exchange of ions across the cell membrane. First, a stimulus opens the sodium channels. Since there are some sodium ions on the outside, and the inside of the neuron is negative relative to the outside, the sodium ions quickly enter the neuron. Sodium is positively charged, so the neuron becomes more positive and begins to depolarize. Potassium channels take a little longer to open; once opened, potassium quickly leaves the cell, reversing the depolarization. At about this time, the sodium channels begin to close, bringing the action potential back to -70 mV (repolarization).

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-lavira: )