The primary function of neurotransmitters in the nervous system is to transmit signals between neurons or from neurons to other cells, such as muscle cells. They are released from the synaptic vesicles of a presynaptic neuron and bind to receptors on the postsynaptic neuron, initiating a response that can either be excitatory or inhibitory. This process is crucial for communication throughout the nervous system, influencing various functions, including movement, emotion, and memory. Dysregulation of neurotransmitter systems can lead to numerous neuropsychiatric disorders.