The Relevance of the Correlation Between Tremor Frequency, Initial Firing Rate of Motoneurons and the Motor Unit's Contraction Time

Abstract

A hypothesis about the origin of the physiological tremor on the basis of other hypotheses is presented. In order to find the muscle fiber candidates that produce the tremor. the muscle fibers and their motoneurons are classified into three groups: The silent fibers (1). the fibers that fire with their initial firing rate (2) and those firing with a high frequency (3). This classification is dynamical. A given muscle fiber can belong to anyone of the three groups. It depends on the threshold of the fiber and the actual excitation level of the motoneuron pool. to which group a fiber belongs. The group two fibers are responsible for, the genesis of the tremor. The reasons for this assumption are: 1. The twitches of the muscle fibers of group two are the least fused. 2. The motoneurons of this group have an augmented tendency to synchronisation. 3. The motor units of group two are the strongest (active) units. Therefore they are overrepresented in the total muscle force.