GENERAL HISTOLOGY

Detailed explanation-1: -The combination of an individual motor neuron and all of the muscle fibers that it innervates is called a motor unit. The number of fibers innervated by a motor unit is called its innervation ratio.

Detailed explanation-2: -A tetanic contraction (also called tetanized state, tetanus, or physiologic tetanus, the latter to differentiate from the disease called tetanus) is a sustained muscle contraction evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate.

Detailed explanation-3: -The CNS activates alpha motor neurons in the spinal cord, which cause extrafusal muscle fibers to contract and thereby resist further stretching. This process is also called the stretch reflex. Beta motor neurons innervate intrafusal muscle fibers of muscle spindles, with collaterals to extrafusal fibres.