Anatomy and innervation ratios in motor units of cat gastrocnemius

Abstract

1. Muscle fibres belonging to single motor units of identified type were studied in frozen sections of cat medial and lateral gastrocnemius muscles. Reconstruction of the distribution of fibres in individual units showed that the territories of all three physiological types present in the cat medial gastrocnemius were quite extensive. Within its territory, fibres belonging to the studied unit were distributed more or less uniformly without localized collections. The density of unit fibres suggests that, in cat medial gastrocnemius, a given region of the muscle may be shared by as many as fifty different muscle units.