Neurotransmitters:

Neurotransmitters are chemical messengers that cross-communicate within the brain and between the brain and the rest of the body. Specifically, they carry signals between neurons by being released from the axon terminal of the transmitting neuron (presynaptic cell), across the synapse, and binding to receptors in the dendrites of the receiving neuron (postsynaptic cell). The neuron’s cell body (soma) synthesizes enzymes needed to create neurotransmitters. These enzymes are transported to the axon terminal and stored in synaptic vesicles, which are thin-walled sacs near the cell membrane. Each vesicle can contain thousands of neurotransmitters. When a nerve cell is activated, the electrical charge of the signal (action potential) causes the synaptic vesicles to fuse with the cell membrane. This releases neurotransmitters into the synapse — to act on the receptor sites. Neurotransmitters send one of three possible actions in their messages: making cells more active (excitatory), blocking/ dampening a cell’s activity (inhibitory), or communicating broadly to more cells (modulatory). Also see Sensory Receptors, Axons, Neurons, and Nerves. Neurotransmitters release various chemicals that rapidly transmit nerve impulses between neurons, including:

• Dopamine (pleasure and reward)
• Serotonin (“happy chemical,” mood)
• Acetylcholine (muscle contraction, memory)
• Glutamate (brain’s most common excitatory neurotransmitter)
• GABA (slows brain by blocking signals. Might help control nerve cell hyperactivity associated with anxiety, stress, fear)
• Norepinephrine (attention and arousal)
• Epinephrine (adrenaline) (responds to stress, triggers fight-or-flight response/FFR)
• Neuropeptides, substance P (pain signals)
• Endorphins (indirect, natural pain relievers)
• Others: Oxytocin, glycine, other peptides