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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/01/09 06:03:27」(JST)

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In physiology, electrotonus refers to the passive spread of charge inside a neuron. Passive means that voltage-dependent changes in membrane conductance do not contribute. Neurons and other excitable cells produce two types of electrical potential:

Electrotonic potential — a non-propagated local potential, resulting from a local change in ionic conductance (e.g. synaptic or sensory that engenders a local current). When it spreads along a stretch of membrane, it becomes exponentially smaller (decrement).
Action potential — a propagated impulse.

Electrotonic potentials represent changes to the neuron's membrane potential that do not lead to the generation of new current by action potentials.^[1] Neurons which are small in relation to their length, such as some neurons in the brain, have only electrotonic potentials (starbust amacrine cells in the retina are believed to have these properties); longer neurons utilize electrotonic potentials to trigger the action potential.

The electrotonic potential travels via electrotonic spread, which amounts to attraction of opposite- and repulsion of like-charged ions within the cell. Electrotonic potentials can sum spatially or temporally. Spatial summation is the combination of multiple sources of ion influx (multiple channels within a dendrite, or channels within multiple dendrites), where temporal summation is a gradual increase in overall charge due to repeated influxes in the same location. Because the ionic charge enters in one location and dissipates to others, losing intensity as it spreads, electrotonic spread is a graded response. It is important to contrast this with the all-or-none law propagation of the action potential down the axon of the neuron.

Electrotonic spread is generally responsible for increasing the voltage of the soma (neuronal cell body) sufficiently to exceed threshold and trigger the action potential; its summation properties described above make it suitable for integrating input from many different sources. Such input may be depolarizing (positive charge, such as sodium) or hyperpolarizing (negative charge, such as chloride).

Electrotonic potentials are conducted faster than action potentials, but attenuate rapidly so are unsuitable for long-distance signaling.

References

^ electrotonic - definition of electrotonic in the Medical dictionary - by the Free Online Medical Dictionary, Thesaurus and Encyclopedia

External links

Khan Academy: Electrotonic and action potential

English Journal

Stochastic Pacing Inhibits Spatially Discordant Cardiac Alternans.

Wilson D1, Ermentrout B2.
Biophysical journal.Biophys J.2017 Dec 5;113(11):2552-2572. doi: 10.1016/j.bpj.2017.10.001.
PMID 29212008

Functional comparison of corticostriatal and thalamostriatal postsynaptic responses in striatal neurons of the mouse.

Arias-García MA1, Tapia D1, Laville JA1, Calderón VM1, Ramiro-Cortés Y1, Bargas J1, Galarraga E2.
Brain structure & function.Brain Struct Funct.2017 Nov 3. doi: 10.1007/s00429-017-1536-6. [Epub ahead of print]
PMID 29101523

Superaligned Carbon Nanotubes Guide Oriented Cell Growth and Promote Electrophysiological Homogeneity for Synthetic Cardiac Tissues.

Ren J1, Xu Q1, Chen X1, Li W1, Guo K1, Zhao Y2, Wang Q1, Zhang Z2, Peng H2, Li YG1.
Advanced materials (Deerfield Beach, Fla.).Adv Mater.2017 Nov;29(44). doi: 10.1002/adma.201702713. Epub 2017 Oct 11.
PMID 29024059

Japanese Journal

Measurement of the action potential of the nerve for the isolation of the nerve in the operative field: An experimental study in rabbit

UJIIE Naoto,NAKANO Toru,SHIMIZU Kazuo
生体医工学 55Annual(Proc), 524-525, 2017
… The amplitude of the action potential of the nerve was evaluated on the nerve or surrounding tissue using by a custom-designed bio-amplifier.</p><p>Results: Two different waveforms of electrotonic spread and the saltatory conduction were recorded. …
NAID 130006077232

術中神経探索を目的とした神経活動電位測定のための基礎的研究

氏家直人,中野徹,清水一夫
生体医工学 55Annual(3AM-Abstract), 190-190, 2017
<p>背景：外科手術時に生じる神経損傷は術後の機能障害の原因となる可能性がある。神経に電気刺激を加え、支配筋肉の筋電図を計測する装置が使用されている。しかし、この方法では神経露出時に損傷をきたす可能性があり、麻痺予防には限界があると言われている。本研究では神経の活動電位を非侵襲的に神経から離れた位置で計測することで、術野における神経の走行を同定するための基礎的実験を行った。方法：17週 …
NAID 130006076927

Partial IK1 blockade destabilizes spiral wave rotation center without inducing wave breakup and facilitates termination of reentrant arrhythmias in ventricles

Kushiyama Yasunori,Honjo Haruo,Niwa Ryoko,Takanari Hiroki,Yamazaki Masatoshi,Takemoto Yoshio,Sakuma Ichiro,Kodama Itsuo,Kamiya Kaichiro
American Journal of Physiology - Heart and Circulatory Physiology 311(3), H750-H758, 2016-09-01
… Partial IK1 blockade destabilizes SW rotation dynamics through a combination of prolongation of the wave length, reduction of excitability, and enhancement of electrotonic interactions, which facilitates termination of ventricular tachyarrhythmias. …
NAID 120005946586