Neurotransmitters are chemicals that allow the spread of signs from neuron to neuron across synapses. They are found at the axon endings of motor neurons, and motivate muscle fibers. They are created by glands for instance the adrenal and pituitary glands.

The brain holds several hundred various types of these chemical messengers that act like communication agents in between various brain cells. These messengers are substances that can manage appetite, mood, sleep, anxiety, temperature, heart rate, aggression, fear as well as many other physical and psychological happenings.

Medical researchers have recognized 3 major classes of neurotransmitters in the brain and these include biogenic amine neurotransmitters, peptide neurotransmitters, and amino acid neurotransmitters.