Mv Transportation Mesa


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Mv Transportation Mesa

Mv Transportation Mesa

Before being stimulated to transmit an electrical impulse, the cell membrane of a neuron is slightly polarized. The fluid inside has a negative charge relative to that outside of the cell because of the balance of positively-charged ions of potassium and sodium and negatively-charged proteins and chloride ions. This polarized state is known as the resting potential. It prepares a neuron for the propagation of an action potential or nerve impulse.

Stages in the Passage of the Action Potential

The membrane potential of an unmyelinated neuron changes during the transmission of an idealized neural impulse. The changes in the membrane potential are brought about by the opening and closing of certain ion channels, allowing the diffusion of ions into and out of the cell, and by protein transport molecules which pump sodium ions out of the cell and potassium ions into the cell.

Stage 1: The Resting Potential

The neuron is at rest. The outside of the cell has an excess of sodium ions (Na+) and the inside of the cell has an excess of potassium ions (K+). The voltage inside the cell is a constant -70 mV (relative to the extracellular fluid). This potential difference is maintained by closed ion channels and the action of the sodium-potassium pump.