Glia - More Than Just Brain Glue

摘要

Glia make up most of the cells in the brain, yet until recently they were believed to have only a passive, supporting role. It is now becoming increasingly clear that these cells have other functions: they make crucial contributions to the formation, operation and adaptation of neural circuitry. The defining characteristic of a neuron is its ability to transmit rapid electrical signals in the form of action potentials. All other neural cells that lack this property are categorized into a broad class termed glia. Neurons are arranged in networks (circuits), and communicate with each other via specialized intercellular adhesion sites called synapses. Neuronal signalling involves the propagation of an action potential down a neurons axonal process to a presynaptic terminal; the depolarization of the terminal and release of neurotransmitters; binding of the released neurotransmitters to receptors on the postsynaptic membrane of another neuron; and the subsequent depolarization of this second neuron, propagating the signal further. Glia do not fire action potentials, but instead surround and ensheath neuronal cell bodies, axons and synapses throughout the nervous system.