Which term best describes chemical messengers that transmit signals between neurons?

• A. Hormones
• B. Neurotransmitters
• C. Enzymes
• D. Receptors

Answer: (B)

Chemical communication between neurons occurs at synapses. The signal is carried by neurotransmitters, chemical messengers released by the sending neuron into the synaptic cleft. They diffuse across the gap and bind to receptors on the receiving neuron, influencing whether that neuron fires an action potential. Neurotransmitters can be excitatory, increasing the chance of firing (for example, glutamate), or inhibitory, decreasing it (like GABA). They are distinct from hormones, which travel through the bloodstream to distant targets, and from enzymes, which catalyze chemical reactions rather than conveying signals. Receptors are the proteins that detect neurotransmitters; they receive the signal but do not carry it across the synapse themselves. In short, these chemical messengers are the neurotransmitters that directly bridge neurons to convey signals.