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THE MADAM C. J. WALKER SCHOOLS Function of Muscles Attached to the bone structure of the body and working together with the various nerves of the body, muscles account for all the movements by which the body is affected. Functioning in connection with the motor nerves they furnish locomotion as in walking, and playing. Working in conjunction with and at the will of the sensory nerves, they control the sense of touch, hearing, smell, taste etc., working in conjunction with the sympathetic nervous system they control the main organs of the body, heart, kidneys, lungs, stomach, etc. Muscles help give shape and beauty to the body, they assist in producing chemical change, expend unused energy, support and pad the body structure and serve as a housing or protection for the blood vessels, nerves and other delicate organism. And just as these examples of muscular function are detailed, many others might be mentioned. Suffice it to say that muscles and nerves working together regulate our lives and are recognized as the master tissues of the body. Composition of Muscles Muscles are composed of cells grouped into thread like fibers bound together in reddish bundles. Each bundle of fibers is wrapped in a covering of connective tissue which keeps the muscles apart and are held together by an intercellular substance or cement. Proteins, carbohydrates, fats and pigment cells represent the mais components of muscles. Classes of Muscles There are three classes of Muscles: 1. STRIATED, CROSS-STRIPED, or VOLUNTARY. 2. NON-STRIATED, SMOOTH, or INVOLUNTARY. 3. CARDIAC, or Heart Muscles. VOLUNTARY MUSCLES are so called because their movements are governed by the cerebrospinal nervous system which directs our will to act. These muscles are attached to the skeleton, are composed of elongated cells closely packed together, their ends overlapping to form parallel bundles. Looked at under the microscope their fibers show a striated or striped appearance. INVOLUNTARY MUSCLES are found in the organs that function without the action of the will, automatically. They are composed 52 TEXT BOOK OF BEAUTY CULTURE of spindle shaped cells much shorter than the cells of voluntary muscles and are held in place by a network of connective tissue carrying nerves and blood-vessels. They are called smooth because they show no stripes. Breathing and the process of digestion are accomplished by the action of involuntary muscles. CARDIAC MUSCLES are found in the heart. The tissue is composed of quadrangular cells joined end to end and grouped in bundles supported by connecting tissue. Muscular tissue is stimulated by impulses conveyed by nerves. Various forms of stimulation are used by doctors in treating certain types of illness traceable to disordered nerves and muscles, and by beauticians in giving massage, such stimuli are called artificial stimuli. All varieties of muscular tissue are well supplied with blood-vessels which exude lymph to nourish the cells. Muscular tissue is also well supplied with nerves. Certain nerve fibers called motor nerves convey impulses from the brain and spine to the muscles and control their action. If a motor nerve is severed or the nerve center in the brain or spine is damaged, the muscle becomes paralyzed, because no impulse is carried to the muscle and there is no action, even though the muscle itself is undamaged. SKELETAL MUSCLES are attached to the skeleton. Almost all occur in pairs. SUPERFICIAL MUSCLES appear at or near the surface. SPHINCTER MUSCLES surround an opening. FASCIA are the sheets of fibrous tissue that bind down muscles and separate them into groups. TENDONS are round or flattened cords of tissue connecting muscle fibers to bones. APONEUROSES are expanded sheets of tendons. LIGAMENTS are strong flexible bands of fibrous tissue that help hold bones together at the joints and serve to hold tendons close to the bones. Origin and Insertion of Muscles Muscles are attached at opposite ends known as the ORIGIN and INSERTION. The term ORIGIN is usually applied to the end more firmly attached and INSERTION applied to the more moveable end. As each muscle acts it contracts lengthwise and pulls 53
