The Motoneurone and its Muscle Fibres

Abstract

This book presents a summary of knowledge concerning somatic motoneurones, the cells which link the central nervous system to the skeletal muscles. There are two functional kinds of such motoneurones: the alpha motoneurones innervating skeletal muscle fibres and the smaller gamma motoneurones which exclusively innervate muscle fibres of complex intramuscular sense organs, the muscle spindles. This book deals primarily with the alpha motoneurones, which together constitute the main output interface of the central nervous system and without which no muscle action is possible. The study of motoneurones is important for general insights as to how neurones work, because the alpha motoneurone is probably the best understood kind of nerve cell so far in neuroscience. Motoneurones of the spinal cord were the first type of central nerve cell to be subjected to detailed physiological measurements, and much is known about how their activity is regulated by synapses from other neurones. For most of the individual neurones within the central nervous system, the precise functional tasks are difficult to define. However, for alpha motoneurones much is known about their short- and long-term interactions with their main targets, the skeletal muscle fibres. Functions of neurones must be analyzed in relation to the response properties of their target cells. Therefore, this book deals with both, summarizing classical as well as recent knowledge concerning motoneurones and their muscle fibres (i.e., motor units).