What is one of the primary roles of neurotransmitters in signal transmission?

Neurotransmitters play a crucial role in facilitating communication between neurons across synapses. When an electrical signal, or action potential, reaches the end of a neuron, it triggers the release of neurotransmitters from vesicles into the synaptic cleft. These chemical messengers then bind to specific receptors on the surface of the receiving neuron, leading to the propagation of the signal.

This process ensures that information can be rapidly transmitted throughout the nervous system, enabling various bodily functions and responses. The effectiveness of this communication is essential for everything from motor control to emotional regulation. Thus, the primary function of neurotransmitters in signal transmission is to enable this chemical communication, making option D the correct choice.