Neurotransmitterfrigjøring

Neurotransmitterfrigjøring, often translated as neurotransmitter release, is a fundamental process in synaptic transmission. It describes the mechanism by which neurons communicate with each other at specialized junctions called synapses. When an electrical signal, known as an action potential, arrives at the presynaptic terminal of a neuron, it triggers a cascade of events leading to the release of chemical messengers called neurotransmitters.

These neurotransmitters are stored in small sacs within the presynaptic terminal called synaptic vesicles. The arrival of the action potential causes voltage-gated calcium channels to open, allowing calcium ions to flow into the terminal. This influx of calcium ions is the critical trigger that promotes the fusion of synaptic vesicles with the presynaptic membrane. Upon fusion, the vesicles release their neurotransmitter contents into the synaptic cleft, the tiny space between the presynaptic and postsynaptic neurons.

Once in the synaptic cleft, the released neurotransmitters diffuse across the gap and bind to specific receptor proteins located on the membrane of the postsynaptic neuron. This binding initiates a response in the postsynaptic neuron, which can be either excitatory (making it more likely to fire an action potential) or inhibitory (making it less likely to fire). The precise effect depends on the type of neurotransmitter and the specific receptor it binds to. Following their action, neurotransmitters are typically removed from the synaptic cleft by reuptake into the presynaptic neuron, enzymatic degradation, or diffusion away from the synapse, thus terminating the signal and allowing for subsequent neurotransmission.