The neurons in the human body are constantly moving and firing signals at all times. When a neuron is stimulated, it fires an impulse to its neighboring neurons. The nerve impulse is called the action potential. Within the body, ions both positive and negative are floating around constantly. Certain areas are more negatively charged, while others are more positively charged. These charges can indicate an action potential. The action potential works when the ions inside and outside of the cell fluctuate. The membrane potential, or difference between the positive and negative areas, can cause the event that triggers the flow of ions across a membrane. A resting neuron is typically negative on the inside of the cell and this resting membrane potential lays at -70 millivolts. The positive sodium ions outside of the membrane and positive potassium ions inside the cell work together in the sodium potassium pump. For every 2 potassium ions that float into the cell, 3 sodium ions are pumped out of the cell. Ion channels are then opened when the membrane potential reaches -55 millivolts. When these channels open, the ions move in and out of the cell depending on the chemical gradient. When a stimulus occurs, the increase in positive ions make the membrane potential exceed -55 millivolts. The resting neuron becomes depolarized, and lets a lot of sodium rush into the cell which creates an action potential. This action potential then flows down the axon of the neuron, and the stimulus occurs. However, when the potassium channels open, the voltage tries to equal out in the cell, and the action potential degrades. This is called the hyperpolarization; the voltage drops to -75 millivolts.
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