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syn-, sym-, sys-

[Gr. syn, with, together with] Prefixes meaning joined, together.


(sin″an-throp′ik) [syn- + anthropo- + -ic] Of nonhuman life, living in a close association with human beings.


(sĭn′ăps) [Gr. synapsis, point of contact] The space between the junction of two neurons in a neural pathway, where the termination of the axon of one neuron comes into close proximity with the cell body or dendrites of another. The electrical impulse traveling along a presynaptic neuron to the end of its axon releases a chemical neurotransmitter that stimulates or inhibits an electrical impulse in the postsynaptic neuron; synaptic transmission is in one direction only. Synapses are susceptible to fatigue, offer a resistance to the passage of impulses, and are markedly susceptible to the effects of oxygen deficiency, anesthetics, and other agents, including therapeutic drugs and toxic chemicals. SYN: synapsis (1). SEE: illus.




Axon terminal synapse


axodendritic s. The synapse between an axon of one neuron and the dendrites of another.

axosomatic s. The synapse between the axon of one neuron and the cell body of another.


(si-nap′sin) A family of proteins found in the presynaptic terminals of nerve axons. When activated by phosphorylation, they assist in the release of neurotransmitters into the neuromuscular junction.


(sĭn-ăp′sĭs) [Gr., point of contact] The process of first maturation division in gametogenesis, in which there is conjugation of pairs of homologous chromosomes forming double or bivalent chromosomes. In the resulting meiotic division, the chromosome number is reduced from the diploid to the haploid number. It is at this stage that crossing over occurs.


(sĭ-năp′tĭk) Pert. to a synapse or synapsis.

synaptic loss

Decreased connectivity between neurons, a characteristic finding in dementia. It can be identified biochemically by a reduction in specific cerebrospinal fluid proteins, or measured radiographically by identifying a reduction in the density of brain gray matter.

synaptic pruning

The elimination from the central nervous system of extraneous neuron connections.


(sin-ap″tō-jĕn′ĕ-sĭs) [synapt(ic) + genesis fr. Gr. gignesthai, to be born] The development of new connections between neurons.


(sĭn″ăp-tŏl′ō-jē) [″ + logos, word, reason] The study of synapses.


(sin″ap-top′ă-thē) [synapt(ic) + -pathy] Any disease or injury to the structures or functioning of nerve synapses.



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