The nerve supply to muscles Skeletal or voluntary muscle receives its nerve supply from the cerebrospinal nervous system as in contrast to heart muscle and smooth muscle which are innervated by the involuntary or autonomic nervous system. The nerves which carry the stimuli to voluntary muscles usually enter the muscles near their middle point. Many of the fibers run directly to the muscle fibers with which they become connected. Other fibers coming from the autonomic nervous system, but associated with the motor fibers to the contractile structures, innervate the blood vessels which supply the muscles. Generally there are fewer nerve fibers in the nerve trunk running to a muscle than there are muscle fibers. The nerve fibers branch before their termination in the muscle and in this manner supply at least one nerve terminal for each muscle fiber. From the nature of its innervation, it seems obvious that all parts of a single muscle fiber must receive their stimuli and therefore respond as a unit. Adjacent fibers in the same muscle may or may not be simultaneously brought into action. The nerve fiber ends within the muscle fiber just beneath the sarcolemma where, after dividing into a number of branches, it ends in a mass of non-muscular and structureless protoplasm, spoken of as the motor end organ. A third substance, neither nerve nor muscl, establishes a connection between the nerve ending and the contractile units of the muscle fiber. In addition to these nerve fibers which carry impulses outward (efferent or centrifugal) to the muscle substance, vascular tissue, and glands, others are employed solely in conducting impulses (afferent or centripetal) toward the central nervous system. The impulses set up by them provide what are commonly called deep, bodily, kinesthetic, or proprioceptive sensibility, necessary for the maintenance of muscle tone and for the awareness of position in our muscles and limbs, and also our posture and movement. These nerves end in the muscles and tendons in what are known as muscle and tendon spindles, respectively. They resemble each other in structure, being fusiform in shape, one to four millimeters in length, and composed of one or more rudimentary muscle fibers encapsulated with connective tissue. One or more nerve fibers enter this capsule and end around the rudimentary fibers in spiral ribbon-like branches.		Home Classes of levers Varieties of muscle Smooth muscle The blood supply to muscles The neurone Cardiac muscle On the nomenclature of skeletal muscles The nerve supply to muscles Structure of a skeletal muscle Central nervous system The reflex arc and reflex action Physiologic properties of muscle Mechanical Changes The effects of temperature on muscular contraction Muscle glycogen, its source and fate The reaction of muscles Oxygen consumption of muscle Determination of the oxygen consumption of muscle The viscosity factor in muscle and muscle efficiency Significance of the recovery heat Production of Electricity