Final answer:
A neurotransmitter is a chemical that is released from the presynaptic neuron and activates receptors on the postsynaptic neuron, facilitating communication between neurons at a synapse. This process is limited in time by the clearance of the neurotransmitter from the synaptic cleft.
Step-by-step explanation:
A neurotransmitter is a chemical released presynaptically due to stimulation and activates postsynaptic receptors; it is the connection between neurons. Neurotransmission involves the release of these signaling molecules by an axon terminal of a neuron (the presynaptic neuron), which then bind to and activate the receptors on the dendrites of another neuron (the postsynaptic neuron) through a very short distance, known as the synaptic cleft. This cleft allows neurotransmitter concentration to be raised and lowered rapidly, facilitating quick communication between neurons.
At a chemical synapse, the neurotransmitter diffuses across the synaptic cleft and binds to receptor proteins on the postsynaptic membrane, changing its potential and allowing for the transmission of the nerve impulse. The neurotransmitter is eventually cleared from the synapse, through enzymatic degradation, neuronal reuptake, or glial reuptake, ensuring that the neurotransmission is a brief and regulated event.
Neurotransmitters can be excitatory or inhibitory, like acetylcholine and GABA, respectively, influencing the likelihood of the postsynaptic neuron to generate an action potential. Understanding this process is crucial in areas such as pharmacology, where drugs can affect synaptic transmission, and in neurobiology, to understand how nerve impulses are communicated in the nervous system.