Electrotonic potential
（重定向自Electrotonic）
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 potentials represent changes to the neuron's membrane potential that do not lead to the generation of new current by action potentials. 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.