Premium
The relation of Rushton's ‘liminal length’ for excitation to the resting and active conductances of excitable cells
Author(s) -
Noble D.
Publication year - 1972
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1972.sp009998
Subject(s) - excitation , rheobase , mathematics , liminality , constant (computer programming) , physics , ionic strength , time constant , chemistry , mechanics , membrane potential , mathematical analysis , quantum mechanics , biochemistry , philosophy , computer science , programming language , aesthetics , aqueous solution , electrical engineering , engineering
1. The minimum (or liminal) length of an excitable cable that must lie above the inward current threshold in order to initiate propagation is derived using a simple polynomial representation of the ionic current—voltage relation. 2. This model is then used to obtain an approximate equation for the liminal length that may easily be applied to excitable cells using experimental measurements of the ionic current. 3. The equations are used to show that the liminal length in cardiac Purkinje fibres is expected to be much smaller than in squid nerve. The values calculated are similar to those obtained by Fozzard & Schoenberg (1972) from strength—duration curves. 4. It is shown that the strength—duration curve for non‐uniform excitation is virtually independent of the resting membrane resistance. The strength—duration time constant may not, therefore, be related to the membrane time constant.