Neurotransmitters

Neurotransmitters are the main method of communication within the nervous system, as well as the basis of communication between the nervous system and other organ systems. There are many different types of neurotransmitters, each of which has a special role and communicates unique information across the body. The nervous system controls when, where and how much neurotransmitter is released, regulating our thoughts, movements, interactions and more.

Neurotransmitter Functions

Neurotransmitters are stored in the axon terminals of neurons. In the axon terminals, the neurotransmitter molecules live in vesicles: small fluid-filled sacs. Each vesicle contains thousands of molecules of neurotransmitters. When an action potential is fired in the neuron, the vesicles fuse with the membrane of the axon terminals, releasing the neurotransmitters into the synaptic cleft.

Neurotransmitters: Chemical Communication

Neurotransmitters regulate almost everything in our body. Some of their more important functions include controlling:

  • Senses

  • Breathing

  • Heartbeat and blood pressure

  • Feelings, thoughts, memories

  • Digestion

There are three main types of neurotransmitters:

  • Excitatory: neurotransmitters that “excite” other neurons, causing action potentials to fire

  • Inhibitory: neurotransmitters that “inhibit” other neurons, preventing action potentials from firing

  • Modulatory: work with other neurotransmitters to “modulate” the effect of chemical signals

Important Neurotransmitters

There are several neurotransmitters that regulate important processes in the body, the chemical signals of the autonomic nervous system.

  • Norepinephrine and epinephrine: key neurotransmitters for the sympathetic nervous system. These chemical signals regulate “fight or flight,” your body’s response to fear and stress. When released, they increase heart rate, blood pressure, and breathing.

  • Acetylcholine: essential neurotransmitter for both the sympathetic and parasympathetic systems. In the parasympathetic nervous system, this chemical signal regulates “rest and digest,”: decreasing heart rate and blood pressure, while increasing digestion.

Once in the synaptic cleft, neurotransmitters bind to receptors in other neurons and tissues. Depending on the neurotransmitter released, the response in other tissues and/or post-synaptic neurons is different. Some neurotransmitters (like glutamate) trigger an action potential in the post-synaptic neuron, while others (like GABA) inhibit an action potential.