Physiological types and histochemical profiles in motor units of the cat gastrocnemius
- 1 November 1973
- journal article
- Published by Wiley in The Journal of Physiology
- Vol. 234 (3), 723-748
- https://doi.org/10.1113/jphysiol.1973.sp010369
Abstract
1. A variety of physiological properties of single motor units have been studied in the gastrocnemius muscle (primarily in the medial head) of pentobarbitone-anaesthetized cats. Intracellular stimulation of individual motoneurones ensured functional isolation of the muscle units innervated by them.2. A system for muscle unit classification was developed using a combination of two physiological properties. Almost all of the units studied could be classified into one of three major types, including two groups with relatively short twitch contraction times (types FF and FR, which were differentiable from one another on the basis of sensitivity to fatigue) and one group with relatively long contraction times (type S, which were extremely resistant to fatigue and were differentiable from FF and FR units on the basis of the shape of unfused tetani). Post-tetanic potentiation of twitch responses was observed in all three muscle unit types. The distributions of axonal conduction velocities for motoneurones innervating FF and FR muscle units were essentially the same, while conduction velocities for motoneurones innervating type S units were, in general, slower.3. Histochemical profiles of muscle units representative of each of the physiological classes present in the gastrocnemius pool were determined using a method of glycogen depletion for muscle unit identification. Each of the physiological categories of muscle units exhibited a corresponding unique set of muscle fibre staining reactions, or histochemical profile. Within each physiological type, all of the units examined had the same histochemical profile. The results generally support the hypothesis that the histochemical characteristics of muscle fibres are meaningfully related to the physiological properties of the same fibres. However, certain limitations in the detailed application of the hypothesis were also apparent.4. Systematic assessment of the histochemical profiles of relatively large numbers of fibres belonging to single muscle units provided strong support for the hypothesis that all of the muscle fibres innervated by a single alpha-motoneurone are histochemically identical.Keywords
This publication has 40 references indexed in Scilit:
- Mammalian Motor Units: Physiological-Histochemical Correlation in Three Types in Cat GastrocnemiusScience, 1971
- The dynamic nature of the so-called “fiber types” of mammalian skeletal muscleExperimental Neurology, 1971
- Accommodation To Current Ramps In Motoneurons of Fast and Slow Twitch Motor UnitsInternational Journal of Neuroscience, 1971
- RELATIONS BETWEEN STRUCTURE AND FUNCTION IN RAT SKELETAL MUSCLE FIBERSThe Journal of cell biology, 1970
- Response of muscle glycogen and phosphorylase to electrical stimulation in trained and nontrained guinea pigsExperimental Neurology, 1970
- The histochemical classification of muscle fibersExperimental Neurology, 1970
- On the relationship of ultrastructural and cytochemical features to color in mammalian skeletal muscleCell and tissue research, 1969
- Differential histochemical effects of muscle contractions on phosphorylase and glycogen in various types of fibres: relation to fatigue.Journal of Neurology, Neurosurgery & Psychiatry, 1968
- MITOCHONDRIAL LOCALIZATION OF OXIDATIVE ENZYMES: STAINING RESULTS WITH TWO TETRAZOLIUM SALTSThe Journal of cell biology, 1961
- CYTOCHEMICAL DEMONSTRATION OF SUCCINIC DEHYDROGENASE BY THE USE OF A NEW p-NITROPHENYL SUBSTITUTED DITETRAZOLEJournal of Histochemistry & Cytochemistry, 1957