Lähettiaineet

Lähettiaineet, also known as neurotransmitters, are chemical messengers used by neurons to transmit signals across a synapse. These molecules are crucial for virtually all functions of the nervous system, enabling communication between nerve cells and between nerve cells and other target cells like muscles or glands.

The process begins when an electrical signal, an action potential, reaches the axon terminal of a neuron. This triggers the release of neurotransmitters from vesicles into the synaptic cleft, the small gap between neurons. These released molecules then diffuse across the cleft and bind to specific receptors on the postsynaptic neuron. This binding event can either excite or inhibit the postsynaptic neuron, depending on the type of neurotransmitter and receptor involved. If excitatory, it increases the likelihood of the postsynaptic neuron firing an action potential. If inhibitory, it decreases this likelihood.

There are numerous types of neurotransmitters, each with distinct roles. Major examples include acetylcholine, which is involved in muscle contraction and memory; dopamine, associated with reward and motivation; serotonin, affecting mood and sleep; and norepinephrine, involved in the body's fight-or-flight response. Glutamate is the primary excitatory neurotransmitter in the central nervous system, while GABA is the primary inhibitory neurotransmitter.

After transmitting their signal, neurotransmitters are typically removed from the synaptic cleft through reuptake by the presynaptic neuron, enzymatic degradation, or diffusion. This rapid clearance is essential for precise and timely neural signaling. Dysregulation of neurotransmitter systems is implicated in a wide range of neurological and psychiatric disorders.