Sähköimpulssit

Sähköimpulssit, also known as electrical impulses or nerve impulses, are transient changes in the electrical potential across the plasma membrane of a cell. These impulses are fundamental to the functioning of the nervous system in animals, enabling rapid communication between neurons and other excitable cells such as muscle cells. The generation and propagation of an electrical impulse are primarily driven by the movement of ions, such as sodium (Na+) and potassium (K+), across the cell membrane through specialized protein channels.

At rest, a neuron maintains a resting potential, a negative charge inside the cell relative to the outside. When a stimulus triggers the cell, voltage-gated ion channels open. Sodium ions rush into the cell, causing a rapid depolarization and making the inside of the membrane positive. This rapid change is the action potential, the electrical impulse itself. Following this peak, potassium channels open, allowing potassium ions to flow out of the cell, repolarizing the membrane back to its negative resting potential.

This process is all-or-none; an impulse either fires with full strength or not at all. The impulse then propagates along the axon of the neuron, a long projection that transmits signals to other cells. In unmyelinated axons, this propagation is continuous, while in myelinated axons, it occurs in a saltatory fashion, jumping between gaps in the myelin sheath, which significantly speeds up transmission. Sähköimpulssit are crucial for sensory perception, motor control, thought, and memory.