Editing Neurotransmitter (section)

===Modulation===
A neurotransmitter may have an excitatory, inhibitory or modulatory effect on the target cell. The effect is determined by the receptors the neurotransmitter interacts with at the post-synaptic membrane. Neurotransmitter influences trans-membrane ion flow either to increase (excitatory) or to decrease (inhibitory) the probability that the cell with which it comes in contact will produce an action potential. Synapses containing receptors with excitatory effects are called Type I synapses, while Type II synapses contain receptors with inhibitory effects.<ref>{{cite journal | vauthors = Peters A, Palay SL | title = The morphology of synapses | journal = Journal of Neurocytology | volume = 25 | issue = 12 | pages = 687–700 | date = December 1996 | pmid = 9023718 | doi = 10.1007/BF02284835 | s2cid = 29365393 }}</ref> Thus, despite the wide variety of synapses, they all convey messages of only these two types. The two types are different appearance and are primarily located on different parts of the neurons under its influence.<ref>{{Cite book|url=https://www.worldcat.org/oclc/881146319|title=Hole's human anatomy & physiology|vauthors=Shier D, Butler J, Lewis R|date=5 January 2015|isbn=978-0-07-802429-0|edition=Fourteenth|location=New York, NY|oclc=881146319}}</ref> Receptors with modulatory effects are spread throughout all synaptic membranes and binding of neurotransmitters sets in motion signaling cascades that help the cell regulate its function.<ref name=":1">{{cite journal | vauthors = Di Chiara G, Morelli M, Consolo S | title = Modulatory functions of neurotransmitters in the striatum: ACh/dopamine/NMDA interactions | journal = Trends in Neurosciences | volume = 17 | issue = 6 | pages = 228–233 | date = June 1994 | pmid = 7521083 | doi = 10.1016/0166-2236(94)90005-1 | s2cid = 32085555 }}</ref> Binding of neurotransmitters to receptors with modulatory effects can have many results. For example, it may result in an increase or decrease in sensitivity to future stimulus by recruiting more or less receptors to the synaptic membrane.{{cn|date=January 2025}}

Type I (excitatory) synapses are typically located on the shafts or the spines of dendrites, whereas type II (inhibitory) synapses are typically located on a cell body. In addition, Type I synapses have round synaptic vesicles, whereas the vesicles of type II synapses are flattened. The material on the presynaptic and post-synaptic membranes is denser in a Type I synapse than it is in a Type II, and the Type I synaptic cleft is wider. Finally, the active zone on a Type I synapse is larger than that on a Type II synapse.{{cn|date=January 2025}}

The different locations of Type I and Type II synapses divide a neuron into two zones: an excitatory dendritic tree and an inhibitory cell body. From an inhibitory perspective, excitation comes in over the dendrites and spreads to the [[axon hillock]] to trigger an [[action potential]]. If the message is to be stopped, it is best stopped by applying inhibition on the cell body, close to the axon hillock where the action potential originates. Another way to conceptualize excitatory–inhibitory interaction is to picture excitation overcoming inhibition. If the cell body is normally in an inhibited state, the only way to generate an action potential at the axon hillock is to reduce the cell body's inhibition. In this "open the gates" strategy, the excitatory message is like a racehorse ready to run down the track, but first, the inhibitory starting gate must be removed.<ref name="Kolb Intro to Brain and Behavior">{{cite book|title=An introduction to brain and behavior|vauthors=Whishaw B, Kolb IQ|date=2014|publisher=Worth Publishers|isbn=978-1429242288|edition=4th|location=New York, NY}}</ref>