Närviimpulssi

Närviimpulssi, known in English as nerve impulse or action potential, is a fundamental process in the nervous system of animals. It is an electrical signal that travels along the membrane of a neuron, or nerve cell. This impulse is crucial for transmitting information from one part of the body to another, enabling everything from simple reflexes to complex thought processes.

The generation of a närviimpulssi begins with a change in the electrical potential across the neuron's cell membrane. When a neuron is stimulated, typically by a chemical signal from another neuron or a sensory receptor, ion channels in its membrane open. This allows positively charged ions, primarily sodium ions, to flow into the cell. This influx of positive charge causes the inside of the neuron to become temporarily more positive than the outside, a phenomenon called depolarization.

If the depolarization reaches a certain threshold, it triggers a rapid and transient reversal of the electrical potential, propagating as an action potential or närviimpulssi along the axon, the long projection of the neuron. Following the peak of the action potential, potassium channels open, allowing potassium ions to flow out of the cell, restoring the negative charge inside and repolarizing the membrane. This sequence of events allows the electrical signal to travel efficiently and quickly to the next neuron or target cell, where it can then trigger another response.