Final answer:
A neurotransmitter is a chemical that carries messages throughout the body, affecting moods, energy levels, and reactions to stress. They enable communication between neurons and are targeted by psychoactive drugs.
Step-by-step explanation:
A neurotransmitter is a chemical that carries messages throughout the body, potentially affecting a person's moods, levels of energy, and reactions to stress. Neurotransmitters are endogenous chemicals that enable neurotransmission, transmitting signals across a synapse from one neuron to another or to muscle cells and gland cells.
Neurotransmitters play a crucial role in the functioning of the nervous system. They help transmit nerve impulses and allow communication between neurons. Some examples of neurotransmitters include dopamine, serotonin, and adrenaline.
Neurotransmitters are also targeted by psychoactive drugs, which affect the central nervous system by influencing neurotransmitter activity in the brain. These drugs can have various effects on mood, behavior, and cognition.