Spontaneous Junctional Activity of Fast and Slow Parietal Muscle Fibres of the Hagfish

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Abstract
The spatial distribution, amplitude distribution and interval distribution of spontaneous Junctional potentials of fast and slow muscle fibres of the myotomal parietal muscle of the hagfish have been studied. The fast muscle fibres are focally innervated with an end‐plate area localized to one end of the fibre whereas the synaptic regions of the slow muscle fibres are distributed along their entire length. The mean distance between the synaptic sites of the slow muscle fibres is less than 0.1 mm. The electrical cable constants of the two types of fibre have been determined by passing square waves of current through the membrane and recording the changes in membrane potential. The specific resistance of the membrane of the slow fibres is unusually high.