Synapses - and the neuron that responds to the NT is...

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Synapses In very general terms, a "synapse" is a structure that enables two adjacent cells to communicate. Very few cells in the vertebrate nervous system are connected by electrical synapses . Cells connected by gap junctions are much more common in vertebrate cardiac and smooth muscle and these junctions connect the cells electrically, such that when one cell is depolarized, adjacent cells also depolarize, allowing for conduction of the signal throughout the entire organ . A much more common connection between cells in vertebrates is the chemical synapse, where the communication method is chemical in nature. One cell releases a chemical that binds to receptors on the second cell, causing a response. Thus, for this discussion, a synapse is a chemical connection between a neuron and its target . The neuron and its target do not touch directly but are separated by the synaptic cleft . For ease of discussion, the neuron that releases the neurotransmitter is presynaptic
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Unformatted text preview: and the neuron that responds to the NT is postsynaptic . Neurotransmitter Release When an AP arrives at the axon terminal, the depolarization of the membrane causes the opening of VG-Ca 2+ channels. Ca 2+ diffuses into cell through the open channels at the terminal and causes the synaptic vesicles to "fuse " with the plasma membrane. This fusion releases the contents of the synaptic vesicle and the NTs enter the synaptic cleft and diffuse away from the site of release. If the neurotransmitters bind to receptors on the target, the receptors change shape and initiate a response in the postsynaptic cell. The response of the target can vary based upon the receptor type and what the target is designed to do. Neuronal targets generally exhibit a local potential, which can be either excitatory or inhibitory . If the presynaptic neuron is innervating a gland, the gland will secrete while muscular targets will contract....
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