MUSCLE PHYSIOLOGY

Detailed explanation-1: -Each lower motor neuron innervates muscle fibers within a single muscle, and all the motor neurons innervating a single muscle (called the motor neuron pool for that muscle) are grouped together into rod-shaped clusters that run parallel to the long axis of the cord for one or more spinal cord segments (Figure 16.2).

Detailed explanation-2: -A mature NMJ is innervated by one motor nerve terminal (Figure 2 Normal); therefore, there is a one-to-one relationship between a given muscle fiber and motor neuron. However, one motor neuron innervates multiple muscle fibers by branching its axon within the innervation target muscle.

Detailed explanation-3: -Any given muscle fiber is innervated by just one motor neuron. A motor neuron and the muscle fibers it innervates are called a motor unit. The muscle fibers within a motor unit usually have similar mechanical properties. Such mechanical homogeneity may simplify the recruitment of motor units.