Relationship of the Sarcoplasmic Reticulum to Sarcolemma in Sheep Cardiac Muscle

Abstract

SINCE Huxley and Taylor1 demonstrated that in striated muscle each myofibril segment probably receives an individual stimulus to contract, electron microscope studies have suggested that the most likely pathway for such stimuli from the sarcolemma to the myofibrils is the sarcoplasmic reticulum2, particularly3 its transverse tubular elements (also named the ‘transverse sarcotubular system’4). Theories about this have recently been elaborated and the evidence has been reviewed5,6. Such theories are necessarily based on the possibility that the membrane of the tubules is polarized and is capable of undergoing depolarization in the same way as the plasma membrane (inner layer of sarcolemma).