Välittäjäaineita

Välittäjäaineita, also known as neurotransmitters, are chemical messengers that transmit signals across a synapse, from a neuron to a target cell. These target cells can be another neuron, a muscle cell, or a gland cell. Neurotransmitters are essential for a wide range of bodily functions, including movement, cognition, mood, and physiological regulation.

The process begins when an electrical impulse, an action potential, reaches the axon terminal of a presynaptic neuron. This triggers the release of neurotransmitters from vesicles into the synaptic cleft, the small gap between the presynaptic and postsynaptic cells. These neurotransmitters then diffuse across the cleft and bind to specific receptors on the membrane of the postsynaptic cell.

This binding event can have excitatory or inhibitory effects on the postsynaptic cell. Excitatory neurotransmitters, such as glutamate, increase the likelihood that the postsynaptic cell will fire an action potential, while inhibitory neurotransmitters, like GABA, decrease this likelihood. Some neurotransmitters can have different effects depending on the type of receptor they bind to.

After transmitting their signal, neurotransmitters are typically removed from the synaptic cleft through reuptake by the presynaptic neuron, enzymatic degradation, or diffusion away from the synapse. This rapid clearance is crucial for allowing the synapse to respond to subsequent signals.

Examples of well-known neurotransmitters include acetylcholine, dopamine, serotonin, norepinephrine, and endorphins. Imbalances in neurotransmitter levels or function are implicated in various neurological and psychiatric disorders.