# Neurotransmitters --- **Neurotransmitters** are molecules that allow [[neurons]] and other parts of the body called "effectors" to communicate with one another. Neurons synthesize and release in order for them to bind onto specific [[channel proteins#Gated Channels|chemically-gated channels]] to initiate a response. Neurotransmitters are released from the [[synapse|synaptic bulb]] of a neuron into the [[synapse]] where they either bind to the appropriate receptors on the other side of the synapse. Neurotransmitters only bind to their receptors very briefly before bouncing back off again into the synaptic cleft. It is generally the case that the neurotransmitters should not stay in the synaptic cleft for long, and there are a few ways to remove a neurotransmitter form the synapse: reuptake, break down, or diffusion. **Neurotransmitter reuptake** is when the molecule is absorbed back into the neuron just as it is. Neurotransmitter break down is facilitated by specialized enzymes that cleave the neurotransmitter. For example, [[acetylcholine]] is broken down by an enzyme called [[acetylcholine|acetylcholinesterase]], and the component parts are then reabsorbed by the releasing neuron. Neurotransmitters can also be removed from the synapse by simply diffusing away from it, where there are caught and absorbed by [[glial cells]]. ![[neurotransmitter.png]] Sometimes we talk about **neurotransmitter systems** which refer to the different neurotransmitters and also their neurons throughout the body, as well as the other neurotransmitters and neuromodulators that interact with it. For example, we might talk about the [[dopamine]] system, or the [[serotonin]] system. ## Neuromodulators **Neuromodulators** are a type of neurotransmitter that are released more broadly and influence how [[neurons]] respond to the specific neurotransmitters. Instead of being released in one specific synapse, they are more diffuse and can affect a whole region of the brain, not just one neuron. They can have a profound impact on your unconscious mind. They are typically larger molecules than neurotransmitters and their affects are slower-acting and longer-lasting than other neurotransmitters. That all being true, it's not a black and white distinction between neuromodulators and **Facilitators** can increase a post-synaptic neuron's sensitivity to a particular neurotransmitter, while **inhibitors** can decrease the post-synaptic neuron's sensitivity. ## Classes of Neurotransmitters Neurotransmitters are typically classed by their molecular make up - [[amino acids|amino acid]] neurotransmitters are derived from amino acids...it seems to me that all neurotransmitters are made from amino acids, so I'm thinking these are just any that aren't specifically one of the other classes. - [[glutamate and aspartate]] - [[GABA]] (gamma-aminobutyric acid) - [[glycine]] - [[serine]] - **monoamine** neurotransmitters are derived specifically from the amino acid **tyrosine** - [[serotonin]] - [[histamine]] - **catecholamines** are a subset of monoamines, characterized by a **catechol** group (a benzene ring with two hydroxyl groups) - [[catecholamines|epinephrine]] - [[catecholamines|norepinephrine]] - [[dopamine]] - **neuropeptides** are short chains of amino acids - [[endorphins]] - [[endorphins|enkephalins]] - [[nausea|substance P]] - [[somatostatin]] ___