Neurotransmitters released into the synaptic gap (or synaptic cleft) reach the target cell primarily through diffusion. Here’s a brief overview of the process:
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Release: When an action potential reaches the presynaptic terminal of a neuron, it triggers the release of neurotransmitters stored in synaptic vesicles. These vesicles fuse with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft.
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Diffusion: Once released, neurotransmitters diffuse across the synaptic cleft. The synaptic cleft is typically only about 20-40 nanometers wide, allowing neurotransmitters to quickly move toward the postsynaptic membrane.
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Binding to Receptors: The neurotransmitters bind to specific receptors on the postsynaptic membrane of the target cell. This binding can lead to various outcomes, such as the opening of ion channels, which may generate an excitatory or inhibitory postsynaptic potential, ultimately influencing whether the target cell will generate an action potential.
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Termination of Signal: After their action, neurotransmitters are removed from the synaptic cleft through several mechanisms, including reuptake into the presynaptic neuron, enzymatic degradation, or diffusion away from the synapse.
Through these steps, neurotransmitters effectively transmit signals between neurons, facilitating communication within the nervous system.