synaptic transmission-1.pptx

- The term neurotransmission is often used synonymously with synaptic transmission, where a neuron communicates with its target cell at a specialized junction called the synapse. Classical synaptic transmission is also called wiring or point-to-point or wired transmission, and involves neurotransmit...

- The term neurotransmission is often used synonymously with synaptic transmission, where a neuron communicates with its target cell at a specialized junction called the synapse. Classical synaptic transmission is also called wiring or point-to-point or wired transmission, and involves neurotransmitter (NT) release by a presynaptic neuron and generation of a rapid response in the target cell. Electrical synapses are less common synapses (in vertebrates, at least) where neurons are directly attached by cell membrane proteins that traverse the membrane of both the pre-synaptic and post- synaptic neuron; an electrical change in one neuron is immediately reflected in the other. Electrical synapses are different from chemical synapses as there is a direct physical connection between the presynaptic and the postsynaptic neuron. This connection takes the form of something called a gap junction, which is essentially a channel that allows ions to flow directly from the presynaptic cell to the postsynaptic cell. Gap junctions contain paired channels in the pre- and postsynaptic neuron membranes, forming pores. These pores are larger than those of the voltage-gated ion channels in chemical synapses, meaning that various substances can diffuse between the neurons. Chemical Synaptic Transmission A chemical synapse is a connection between two neurons, where nerve impulses are relayed by a neurotransmitter from the axon of a presynaptic (sending) neuron to the dendrite of a postsynaptic (receiving) neuron. In a chemical synapse, the gap between neurons is called the synaptic cleft or synaptic gap. During chemical synaptic transmission, the action potential (an electrical impulse) triggers the synaptic vesicles of the pre-synaptic neuron to release neurotransmitters (a chemical message). These neurotransmitters diffuse across the synaptic cleft (the gap between the pre and post- synaptic neurons) and bind to specialized receptor sites on the post-synaptic neuron.