Final answer:
Neurotransmitters are the substances released when a nerve impulse reaches the terminal buttons of a neuron. They cross the synapse and help perpetuate the signal to the next neuron. These chemical communicators can have various effects based on their type and the receptors they bind to.
Step-by-step explanation:
When a nerve impulse reaches the terminal buttons at the end of a neuron's axon, chemical communicators known as neurotransmitters are released. These neurotransmitters traverse the synaptic cleft between neurons and bind to receptors on the membrane of the dendrite of the adjacent neuron, continuing the transmission of the nerve impulse through the nervous system.
Neurotransmitters can have excitatory or inhibitory effects, and their precise function depends on the type of neurotransmitter and the receptor to which it binds. For instance, dopamine (C8H11NO2) is a neurotransmitter that's involved in various neurological processes including mood regulation, motor control, and reward mechanisms.
It is important to note that not all signaling molecules function as neurotransmitters. The adrenergic system, for example, involves both neurotransmitters and hormones, depending on where the molecule is released. Norepinephrine can act as a neurotransmitter when released from postganglionic sympathetic fibers, or as a hormone when secreted by the adrenal gland into the bloodstream.