neuronilähettämän

Neuronilähettämä, often translated as neurotransmitter, is a chemical messenger that transmits signals across a chemical synapse from one neuron to another neuron, or from a neuron to a target effector cell. These molecules are stored in vesicles within the presynaptic terminal of a neuron and are released into the synaptic cleft when an action potential arrives at the terminal. Once in the synaptic cleft, neurotransmitters diffuse across to bind to specific receptors on the postsynaptic membrane of the target cell.

The binding of a neurotransmitter to its receptor can have various effects on the postsynaptic cell. It can cause depolarization, making the cell more likely to fire an action potential (excitatory effect), or it can cause hyperpolarization, making the cell less likely to fire an action potential (inhibitory effect). Some neurotransmitters can also have more complex effects, modulating the activity of the postsynaptic cell over longer periods.

There are many different types of neurotransmitters, each with distinct chemical structures and functions. Some of the most well-known include acetylcholine, which plays a role in muscle contraction and learning, dopamine, involved in reward and motivation, serotonin, affecting mood and sleep, and glutamate, the primary excitatory neurotransmitter in the central nervous system.

After transmitting their signal, neurotransmitters are typically removed from the synaptic cleft either by enzymatic degradation or by reuptake into the presynaptic neuron or surrounding glial cells. This process ensures that the signal is transient and that the synapse is ready to receive new signals. The precise regulation of neurotransmitter release, binding, and removal is crucial for proper nervous system function.