| synaphoceptors | Receptors stimulated by direct contact. Origin: G. Synaphe, contact, + L. Recipio, to receive (05 Mar 2000) |
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| synapse | <physiology> A connection between excitable cells, by which an excitation is conveyed from one to the other. 1. Chemical synapse: one in which an action potential causes the exocytosis of neurotransmitter from the presynaptic cell, which diffuses across the synaptic cleft and binds to ligand gated ion channels on the post synaptic cell. These ion channels then affect the resting potential of the post synaptic cell. 2. Electrical synapse: one in which electrical connection is made directly through the cytoplasm, via gap junctions. 3. Rectifying synapse: one in which action potentials can only pass across the synapse in one direction (all chemical and some electrical synapses). 4. Excitatory synapse: one in which the firing of the presynaptic cell increases the probability of firing of the postsynaptic cell. 5. Inhibitory synapse: one in which the firing of the presynaptic cell reduces the probability of firing of the postsynaptic cell. (10 Jan 1998) |
| synapses | Specialised junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialised region of a muscle or secretory cell. Neurons may also communicate through direct electrical connections which are sometimes called electrical synapses; these are not included here but rather in gap junctions. (12 Dec 1998) |
| synapsin I | A fibrous phosphoprotein that links synaptic vesicles together in the axon terminal; synapsin I is a substrate for certain kinases; phosphorylation of synapsin I allows release of neurotransmitters. (05 Mar 2000) |
| synapsins | <protein> Family of phosphoproteins associated with synaptic vesicles and implicated in control of release. Synapsin Ia (84 kD) and Ib (80 kD) are alternatively spliced variants as are synapsins IIa (74 kD) and IIb (55 kD). Can be phosphorylated by several protein kinases. Thought to be involved in regulation of neurotransmitter release at synapses. (10 Jan 1998) |
| synapsis | <cell biology> The specific pairing of the chromatids of homologous chromosomes during prophase I of meiosis. It allows crossing over to take place. (18 Nov 1997) |
| synapta | <zoology> A genus of slender, transparent holothurians which have delicate calcareous anchors attached to the dermal plates. Origin: NL, fr. Gr. Fastened together; with + to fasten. Source: Websters Dictionary (01 Mar 1998) |
| synaptase | <chemistry> A ferment resembling diastase, found in bitter almonds. Cf. Amygdalin, and Emulsin. Origin: Gr. Fastened together + diastase. Source: Websters Dictionary (01 Mar 1998) |
| synaptic | <physiology> Pertaining to or affecting a synapse or synapsis. (10 Jan 1998) |
| synaptic boutons | The somewhat enlarged, often club-shaped endings by which axons make synaptic contacts with other nerve cells or with effector cells (muscle or gland cells). As isolated, by homogenizing brain or spinal cord, they contain acetylcholine and the related enzymes. Terminals contain neurotransmitters of various kinds, sometimes more than one. These can be demonstrated by chemical analysis and immunocytochemical methods. See: synapse. Synonym: axonal terminal boutons, end-feet, neuropodia, pieds terminaux, synaptic boutons, synaptic endings, synaptic terminals, terminal boutons, bouton terminaux. (05 Mar 2000) |
| synaptic cleft | <physiology> The narrow space between the presynaptic cell and the postsynaptic cell in a chemical synapse, across which the neurotransmitter diffuses. (10 Jan 1998) |
| synaptic conduction | The conduction of a nerve impulse across a synapse. (05 Mar 2000) |
| synaptic endings | The somewhat enlarged, often club-shaped endings by which axons make synaptic contacts with other nerve cells or with effector cells (muscle or gland cells). As isolated, by homogenizing brain or spinal cord, they contain acetylcholine and the related enzymes. Terminals contain neurotransmitters of various kinds, sometimes more than one. These can be demonstrated by chemical analysis and immunocytochemical methods. See: synapse. Synonym: axonal terminal boutons, end-feet, neuropodia, pieds terminaux, synaptic boutons, synaptic endings, synaptic terminals, terminal boutons, bouton terminaux. (05 Mar 2000) |
| synaptic membranes | Cell membranes associated with synapses. Both presynaptic and postsynaptic membranes are included along with their integral or tightly associated specializations for the release or reception of transmitters. (12 Dec 1998) |
| synaptic phase | <cell biology> The specific pairing of the chromatids of homologous chromosomes during prophase I of meiosis. It allows crossing over to take place. (18 Nov 1997) |