Editing Neuron (section)

==Mechanisms for propagating action potentials==
{{Main|Action potential}}
In 1937 [[John Zachary Young]] suggested that the [[squid giant axon]] could be used to study neuronal electrical properties.<ref>{{cite web |first = Eric H. |last = Chudler | name-list-style = vanc |title = Milestones in Neuroscience Research |url = http://faculty.washington.edu/chudler/hist.html |work = Neuroscience for Kids |access-date = 2009-06-20}}</ref> It is larger than but similar to human neurons, making it easier to study. By inserting electrodes into the squid giant axons, accurate measurements were made of the [[membrane potential]].

The cell membrane of the axon and soma contain voltage-gated ion channels that allow the neuron to generate and propagate an electrical signal (an action potential). Some neurons also generate [[subthreshold membrane potential oscillations]]. These signals are generated and propagated by charge-carrying [[ions]] including sodium (Na<sup>+</sup>), potassium (K<sup>+</sup>), chloride (Cl<sup>−</sup>), and [[Calcium signaling|calcium (Ca<sup>2+</sup>)]].

Several stimuli can activate a neuron leading to electrical activity, including [[Mechanoreceptor|pressure]], stretch, chemical transmitters, and changes in the electric potential across the cell membrane.<ref>{{cite web|first1=Joe |last1=Patlak |first2=Ray |last2=Gibbons | name-list-style = vanc |title=Electrical Activity of Nerves |url=http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |work=Action Potentials in Nerve Cells |date=2000-11-01 |access-date=2009-06-20 |url-status=dead |archive-url=https://web.archive.org/web/20090827220335/http://physioweb.med.uvm.edu/cardiacep/EP/nervecells.htm |archive-date=August 27, 2009 }}</ref> Stimuli cause specific ion-channels within the cell membrane to open, leading to a flow of ions through the cell membrane, changing the membrane potential. Neurons must maintain the specific electrical properties that define their neuron type.<ref name="Harris-Warrick">{{cite journal |last1=Harris-Warrick |first1=RM |title=Neuromodulation and flexibility in Central Pattern Generator networks. |journal=Current Opinion in Neurobiology |date=October 2011 |volume=21 |issue=5 |pages=685–92 |doi=10.1016/j.conb.2011.05.011 |pmid=21646013|pmc=3171584 }}</ref>

Thin neurons and axons require less [[metabolism|metabolic]] expense to produce and carry action potentials, but thicker axons convey impulses more rapidly. To minimize metabolic expense while maintaining rapid conduction, many neurons have insulating sheaths of [[myelin]] around their axons. The sheaths are formed by [[glia]]l cells: [[oligodendrocyte]]s in the central nervous system and [[Schwann cell]]s in the peripheral nervous system. The sheath enables action potentials to travel [[saltatory conduction|faster]] than in unmyelinated axons of the same diameter, whilst using less energy. The myelin sheath in peripheral nerves normally runs along the axon in sections about 1&nbsp;mm long, punctuated by unsheathed [[node of Ranvier|nodes of Ranvier]], which contain a high density of voltage-gated ion channels. [[Multiple sclerosis]] is a neurological disorder that results from the demyelination of axons in the central nervous system.

Some neurons do not generate action potentials but instead generate a [[graded potential|graded electrical signal]], which in turn causes graded neurotransmitter release. Such [[non-spiking neurons]] tend to be sensory neurons or interneurons, because they cannot carry signals long distances.