Answer
A motor unit consists of one motor neuron and all the muscle fibers it innervates. The number of muscle fibers innervated by one motor neuron varies widely (3 to>2000), dependent on the function of the muscle.
In motor units that are responsible for fine and precisely controlled muscular movements, each motor neuron innervates few (3-10) muscle fibers. In contrast, where strength is more important than fine control, each motor neuron innervates a large number of muscle fibers ( 200-3000).
Work Step by Step
Examples; Relatively small motor units
In the extraocular muscles, a motor unit may innervate as few as five (5-10) muscle fibers
In finger muscle motor units, the ratio of motor neurons to muscle fibers is about 300:1
Large motor units:
ln strong muscles such as the gluteal muscles of the buttocks, and the gastrocnemius of the
of the leg (calf muscle), the ratio of motor neurons to muscle fibers may be more than 2000:1
