Dendrite

A dendrite (from Greek δένδρον déndron, "tree") or dendron is a branched protoplasmic extension of a nerve cell that propagates the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project. Electrical stimulation is transmitted onto dendrites by upstream neurons (usually via their axons) via synapses which are located at various points throughout the dendritic tree. Dendrites play a critical role in integrating these synaptic inputs and in determining the extent to which action potentials are produced by the neuron. Dendrites are one of two types of protoplasmic protrusions that extrude from the cell body of a neuron, the other type being an axon. Axons can be distinguished from dendrites by several features including shape, length, and function. Dendrites often taper off in shape and are shorter, while axons tend to maintain a constant radius and be relatively long. Typically, axons transmit electrochemical signals and dendrites receive the electrochemical signals, although some types of neurons in certain species lack axons and simply transmit signals via their dendrites. Dendrites provide an enlarged surface area to receive signals from the terminal buttons of other axons, and the axon also commonly divides at its far end into many branches (telodendria) each of which ends in a nerve terminal, allowing a chemical signal to pass simultaneously to many target cells. Typically, when an electrochemical signal stimulates a neuron, it occurs at a dendrite and causes changes in the electrical potential across the neuron's plasma membrane. This change in the membrane potential will passively spread across the dendrite but becomes weaker with distance without an action potential. An action potential propagates the electrical activity along the membrane of the neuron's dendrites to the cell body and then afferently down the length of the axon to the axon terminal, where it triggers the release of neurotransmitters into the synaptic cleft.