Editing Action potential (section)

===Chemical synapses===
{{Main|Chemical synapse|Neurotransmitter|Excitatory postsynaptic potential|Inhibitory postsynaptic potential}}

In general, action potentials that reach the synaptic knobs cause a [[neurotransmitter]] to be released into the synaptic cleft.<ref group=lower-alpha>{{cite book | vauthors = Süudhof TC | chapter = Neurotransmitter Release | title = Pharmacology of Neurotransmitter Release | volume = 184 | issue = 184 | pages = 1–21 | year = 2008 | pmid = 18064409 | doi = 10.1007/978-3-540-74805-2_1 | isbn = 978-3-540-74804-5 | series = Handbook of Experimental Pharmacology }}</ref> Neurotransmitters are small molecules that may open ion channels in the postsynaptic cell; most axons have the same neurotransmitter at all of their termini. The arrival of the action potential opens voltage-sensitive calcium channels in the presynaptic membrane; the influx of calcium causes [[synaptic vesicle|vesicles]] filled with neurotransmitter to migrate to the cell's surface and [[exocytosis|release their contents]] into the [[synaptic cleft]].<ref group=lower-alpha>{{cite journal | vauthors = Rusakov DA | title = Ca2+-dependent mechanisms of presynaptic control at central synapses | journal = The Neuroscientist | volume = 12 | issue = 4 | pages = 317–26 | date = August 2006 | pmid = 16840708 | pmc = 2684670 | doi = 10.1177/1073858405284672 }}</ref> This complex process is inhibited by the [[neurotoxin]]s [[tetanospasmin]] and [[botulinum toxin]], which are responsible for [[tetanus]] and [[botulism]], respectively.<ref group=lower-alpha>{{cite journal | vauthors = Humeau Y, Doussau F, Grant NJ, Poulain B | title = How botulinum and tetanus neurotoxins block neurotransmitter release | journal = Biochimie | volume = 82 | issue = 5 | pages = 427–46 | date = May 2000 | pmid = 10865130 | doi = 10.1016/S0300-9084(00)00216-9 }}</ref>

[[Image:Gap cell junction-en.svg|thumb|right|[[Electrical synapse]]s between excitable cells allow ions to pass directly from one cell to another, and are much faster than [[chemical synapse]]s.|alt=Electrical synapases are composed of protein complexes that are imbedded in both membranes of adjacent neurons and thereby provide a direct channel for ions to flow from the cytoplasm of one cell into an adjacent cell.]]