synapse (redirected from axosomatic synapse)

synapse (sĭn`ăps), junction between various signal-transmitter cells, either between two neurons or between a neuron and a muscle or gland. A nerve impulse reaches the synapse through the axon, or transmitting end, of a nerve cell, or neuron. Most axons have terminal knobs that respond to the impulse by releasing a chemical substance known as a neurotransmitter. Crossing a gap of less than a millionth of an inch (the synaptic cleft), the neurotransmitter contacts the adjacent muscle, gland, or nerve cell or its branch receptor sites, called dendrites. Neurotransmitters known to scientists today include acetylcholine, epinephrine, and norepinephrine. These neurotransmitters either excite or inhibit the recipient cell, depending on the particular reaction between the two. In other words, a neurotransmitter may inhibit activity in the post-synapse cell when attached to a certain receptor, but may excite activity when attached to others. If sufficiently excited, the second cell transmits the impulse, typically to a muscle, gland, or another synapse. An electric synapse, unlike a chemical one, uses channels known as gap junctions to permit direct transmission of signals between neurons. Such synapses are found in the human body, within many organs and in the glial cells of the nervous system. Electrical synapses are also found among invertebrates and some lower vertebrates.

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synapse

Site of transmission of electric nerve impulses between two nerve cells or between a nerve cell and a gland or muscle cell. At chemical synapses, impulses are transmitted across microscopic spaces via chemical substances called neurotransmitters. In electric synapses, direct communication between nerve cells whose membranes are fused is possible because ions flow between the cells through channels. Electric synapses are found mainly in invertebrates and lower vertebrates; they transmit messages faster than chemical synapses. Chemical transmission seems to have evolved in large, complex vertebrate nervous systems, in which multiple messages must be transmitted over long distances.

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synapse

the point at which a nerve impulse is relayed from the terminal portion of an axon to the dendrites of an adjacent neuron

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synapse [′si‚naps]

(neuroscience)

A site where the axon of one neuron comes into contact with and influences the dendrites of another neuron or a cell body.