Beroë muscle fibers are single cells which may be 20-40 micrometer in diameter in mature specimens. Longitudinal muscles may be 6 cm or more long. There is no striation pattern and the muscles were observed to contract in a tonic fashion when stretched. They are innervated by a nerve net, and external recording revealed what are probably nerve net impulses. Intracellular stimulation of the muscles themselves was found to initiate large propagating action potentials which were recorded intracellularly. The action potentials were insensitive to tetrodotoxin (10(-5) g/ml), tetraethylammonium ions (50 mM), MnCl2 (25 mM), and low concentrations of verapamil (2 X 10(-6) g/ml). Full-size action potentials were recorded in sodium- or calcium-deficient salines, but were small and graded in salines deficient in both sodium and calcium. Cable analysis yielded mean values for lambda (1.95 mm), Ri (154 omega cm), Rm (9,253 omega cm2), and tau m (13.9 ms). The conduction velocity depended primarily on fiber diameter and maximum rate of rise of the action potential and could be predicted from the theoretical analysis of Hunter et al. (1975 Prog. Biophys. Mol. Biol. 30: 99-144). The calculated membrane capacity (less than microF/cm2) indicates little infolding of the surface membrane, a conclusion which is in agreement with anatomical studies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.