Electrotonus

Part of speech: noun

Definitions

1. A change in the excitability of a nerve or muscle fibre that occurs when a steady electric current passes through a region of it
2. The altered electrical state of nerve tissue surrounding a region where a constant direct current is applied to the cell
3. A localized shift in the electrical excitability of living tissue produced by a continuous current flowing along a nerve or muscle

Etymology: Electrotonus is a word built from two pieces that each carry a long history. The first, "electro-", traces back through French "électro-" to the Ancient Greek "ḗlektron", meaning amber, the yellowish fossil resin that gives us the modern sense of electricity. Ancient Greeks noticed that rubbed amber attracted light objects, and the Latin "ēlectrum" carried that name forward. The second part, "tonus", is Latin for tension or tone, borrowed in its own right into English. Put together, the compound describes the state of a nerve when an electric current is passing through it. Physiologists used it to name the changes in a nerve's excitability that occur near a current, a sense the word still holds in physiology today.