Nerve-Muscle Interaction

In the second century, Galen recognized that nerve and muscle were functionally inseparable since contraction of muscle occurred only if the nerves supplying that muscle were intact. He therefore concluded that the shortening of a muscle was controlled by the central nervous sytem while the extension of a muscle could occur in the absence of innervation. Nerves, he thought, were the means of transport for animal spirits to the muscles; the way in which animal spirits may bring about contraction dominated the study of muscle physiology from that time until the historical discovery of Galvani that muscle could be stimulated electrically and that nerve and muscle were themselves a source of electrical energy. It is now well known that nerves conduct electrically and that transmission from nerve to striated muscle is mediated by the chemical which is liberated from nerve terminals onto the muscle membrane. In vertebrates this chemical is acetylcholine (ACh). Thus the concept of spirits that are released from nerves and control muscle contraction directly, is no longer tenable. Nevertheless the concept of 'substances' transported down nerv~s which directly control many aspects of muscle has not been abandoned, and has in fact been frequently reinvoked to account for the long-term regula tion of many characteristics of muscle (see review by Gutmann, 1976) and for the maintenance of its structural integrity.

Inhalt
1 Early muscle development.- 1.1 Early stages of muscle fibre development.- 1.2 Lack of specialization of myotubes.- 1.3 The dependance of the structural integrity of the developing muscle fibres on innervation.- 2 Development of the motor nerves and their encounter with muscle fibres.- 2.1 Origin of motor nerve fibres and their growth into the periphery.- 2.2 Development of nerves and muscles and their interdependence.- 2.3 Development of stable nerve-muscle connections.- 2.4 Are nerve-muscle connections specified?.- 2.5 Conclusions.- 3 Development of the neuromuscular junction.- 3.1 Distribution of ACh receptors during early development.- 3.2 Stabilization of chemosensitivity at the neuromuscular junction.- 3.3 Development of the subneural apparatus.- 3.4 Formation of stable nerve-muscle connections.- 3.5 Changes of chemosensitivity outside the endplate.- 3.6 Maintenance of endplate chemosensitivity.- 3.7 Pattern of innervation of muscle fibres.- 3.8 Conclusions.- 4 Differentiation of skeletal muscle fibres.- 4.1 The muscles of lower vertebrates and birds.- 4.2 Mammalian muscles.- 4.3 How is differentiation into different fibre types induced?.- 4.4 Conclusions.- 5 The effects of denervation on muscle fibre properties and the regulation of chemosensitivity.- 5.1 Morphological changes following denervation.- 5.2 Metabolic changes in denervated muscles.- 5.3 Changes in contractile properties of denervated muscle.- 5.4 Changes in electrical properties of the membrane on denervation.- 5.5 Changes of chemosensitivity at the endplate.- 5.6 Conclusions.- 6 Re-innervation of the muscle by its motor nerve.- 6.1 Nerve growth.- 6.2 Establishment of nerve-muscle connections by the regenerating nerve fibre.- 6.3 Maturation of the regenerated axon and recovery of the muscle.- 6.4 Effects of muscle on normal and regenerating motor nerve terminals.- 6.5 Conclusion.- 7 The mammalian motor unit.- 7.1 Specialization of motoneurones.- 7.2 Matching properties of different motoneurones to the muscle fibres they supply.- 7.3 Specialization of the vascular bed of slow and fast mammalian muscles.- 7.4 How is the matching of muscle fibres to their motoneurones brought about?.- 7.5 Development of the motor unit.- 7.6 Conclusions.- 8 Plasticity in the neuromuscular system.- 8.1 Can different skeletal muscle fibres be transformed from one type to another?.- 8.2 Can the characteristic properties of neurones and their terminals be altered?.- 8.3 Specificity of nerve-muscle connections.- 8.4 Conclusions.- 9 Some examples of disturbances of nerve-muscle interactions.- 9.1 Disturbances caused by a change in the function of the motoneurone.- 9.2 Consequences of disease of the motoneurone, or axon.- 9.3 Disturbance due to disease of the neuromuscular junction.- 9.4 Disease of the muscle.- 9.5 Retrograde influences on the motoneurone.- References.