MEDICAL PHYSIOLOGY

Detailed explanation-1: -the ratio expressing the number of muscle fibers innervated by a single motor axon. It may vary from 3 muscle fibers per axon for small muscles in the fingers to 150 muscle fibers per axon for large muscle bundles of the arms and legs. The lower the ratio, the finer is the control of movements.

Detailed explanation-2: -The innervation ratio defines the number of muscle fibers innervated by a single motor neuron. Low innervation ratios (approximately 100) occur in the hand, where fine gradations in muscle force are needed for fine motor control.

Detailed explanation-3: -Thus, there is a one-to-one relationship between a muscle and a motor neuron pool. Each individual muscle fiber in a muscle is innervated by one, and only one, motor neuron (make sure you understand the difference between a muscle and a muscle fiber).

Detailed explanation-4: -A larger innervation ratio means that there are many muscle fibers comparatively to the motor units that innervate them. A smaller innervation ratio means that there are fewer muscle fibers innervated compared to the number of motor units.