Final answer:
An electrical signal within a single neuron is transferred to a target cell over a very short distance as a chemical messenger called a neurotransmitter, which crosses the synaptic cleft and binds to receptors on the postsynaptic cell.
Step-by-step explanation:
In the nervous system, an electrical signal that travels across a neuron, a specialized cell, reaches the end of its long extension called an axon. This signal is then transferred to the target cell over a short distance in the form of a chemical messenger called a neurotransmitter. Neurotransmitters such as serotonin or norepinephrine are stored in vesicles and released into the small gap called the synaptic cleft by a process known as exocytosis. The molecules then travel across the synaptic cleft and bind to receptors on the surface of the next cell, the postsynaptic cell, to continue the signal. This chemical synapse allows for rapid and local signal transmission, which is crucial for quick responses necessary for functions like movement, sensation, and cognition.