Giant Smooth Muscle Cells of Berok" Ultrastructure, Innervation, and Electrical Properties

I N T R O D U C T I O N Beroid ctenophores possess a system of mesogleal muscle fibers organized into several distinct fields and innervated by processes of the ectodermal nerve net (Hertwig, 1880; Franc, 1970; Hernandez-Nicaise , 1973 a,b,c). Each muscle fiber is a single cell tha t appears to contract in a tonic fashion when stretched and displays no striation pat tern. This together with other criteria suggest tha t the fibers m a y be classified as smooth muscle. T h e y run independen t ly for considerable distances (6 cm or more) and are large enough (20-40 #m in diameter) to permit intracel lular recording. Intracel lular s t imulat ion initiates large propaga t ing action potentials wi thout not iceably shortening the muscle. J. GEN. PHYSIOL. (~)The Rockefeller University Press 9 0022-1295/80/01/0079o/27 $1.00 Volume 75 January 1980 79-105 79 on Jne 2, 2017 D ow nladed fom Published January 1, 1980