Chapter 7: Muscular System Theory Lecture Outline Objectives 1. Describe the function of muscle 2. Describe each of the muscle groups 3. List the characteristics of muscle 4. Describe how pairs of muscles work together 5. Explain origin and insertion of muscle 6. Locate the important skeletal body muscles 7. Describe the function of these skeletal muscles 8. Discuss how sports training affects muscles 9. Identify some common muscle disorders 10. Define the key words that relate to this chapter Introduction Collectively, there are over 650 different muscles in the human body. The ability to move is an essential activity of the living human body, which is made possible by the unique function of contractility in muscles. Muscles are responsible for: Body heat to maintain body temperature Body movement Body form and shape to maintain posture Types of Muscles Body movements are determined by one or more of the three principle types of muscle tissue; they are skeletal, smooth (visceral) and cardiac Skeletal muscle a. Also called voluntary muscle because they are Under conscious control b. Skeletal muscles are attached to the bones of the skeleton A whole skeletal muscle is considered an organ of the muscular system (i.e. biceps muscle or deltoid muscle); each organ or muscle consists of skeletal muscle tissue, connective tissue, nerve tissue and blood or vascular tissue. An individual skeletal muscle such as the biceps muscle may consist of hundreds, or even thousands, of muscle fibers bundled together and wrapped in a connective tissue covering. c. Each muscle cell is known as a muscle fiber Smooth muscle a. Not under conscious control; for this reason they are also called involuntary muscles b. Found in the walls of internal organs, including the stomach, intestines, uterus and blood vessels c. Actions are Controlled by the autonomic nervous system; they act slowly and do not tire easily Cardiac muscle a. Found In the heart only b. Not under conscious control, they are involuntary c. Requires a continuous supply of oxygen to function Special Circular Muscles Sphincter or dilator muscles a. Located in the openings between the esophagus and stomach, and the stomach and small intestine b. Function is to control the passage of substances by opening and closing
Summary of Muscle Tissue Feature Skeletal Smooth (Visceral) Cardiac Location Attached to bones Walls of internal organs and Heart blood vessels Function Produce body movement Contraction of visceral and blood vessels Pump blood through heart and blood vessels Cell Shape Cylindric Spindle shaped, tapered ends Cylindric, branching Number of Nuclei Many One One Striations Present Absent Present Type of Control Voluntary Involuntary Involuntary Characteristics of Muscles All muscles, whether they are skeletal, smooth or cardiac, have 4 common characteristics which produce a veritable mechanical device capable of complex, intricate movement Contractibility a. The ability to shorten or contract in response to stimuli b. Quality possessed by no other body tissue Excitability or irritability a. The ability to receive and respond to a stimulus from the nervous system b. Characteristic of both muscle and nervous cells Extensibility o The ability of the muscle to be stretched or extended Elasticity o The ability to recoil or return to the original shape and length after contraction or extension Muscle Attachments and Functions Over 650 muscles in the body Muscles must be attached to bones for leverage Muscles only pull, never push Attached to bone by tendons Skeletal muscles are attached to bones in such a way as to bridge joints so that when a skeletal muscle contracts, the bone to which it is attached will move Muscles are attached at both ends Attachments may be to bones, cartilage, ligaments, tendons, skin or to each other Origin and insertion a. Origin is the part of a skeletal muscle that is attached to a fixed structure or bone b. Insertion is the other end, attached to a movable part Prime mover and antagonist Muscles are arranged in pairs so that one produces movement in a single direction and the other does so in the opposite direction Synergists Stabilize joint activity Sources of Energy and Heat When muscles do their work, they not only move the body but also produce the heat which our bodies need Narrow range of normal body temperature o 98.6 F to 99.8 F For muscles to contract and do their work, they need energy; the immediate or initial source of energy for muscle contraction is ATP ATP (adenosine triphosphate) a. To make ATP, cells Need oxygen, glucose, and other material to make
b. By-product is lactic acid During this process, lactic acid, a by-product of cell metabolism, builds up Contraction of Skeletal Muscle Movement of muscles occurs as a result of two major events: Myoneural stimulation Skeletal muscles must be stimulated by nerve impulses to contract Contraction of muscle proteins Skeletal muscle contraction begins with the action potential which travels along the muscle fiber length; the basic source of energy ATP serves as a trigger mechanism by allowing energy transfer to the protein molecules within the muscle fibers. Once begun, the action potential travels over the entire surface conducting the electric impulse form one end of the cell to the other resulting in the contraction of the muscle cell Effects of Aging Muscle atrophy Fibrous tissue replaces the muscle tissue Decrease in muscular strength and endurance Loss of energy storage o Fatigue Muscle Fatigue Caused by accumulation of lactic acid in the muscles When not enough oxygen can be transported to oxidize all the glucose o Muscles contract anaerobically Excess lactic acid causes fatigue and cramps Need to repay oxygen debt o Amount of oxygen needed to change the lactic acid back to glucose and other substances to be used by the muscle cells Muscle Tone Muscle tone o Muscles are always slightly contracted and ready to pull Muscle tone is achieved through Proper nutrition and regular exercise Muscle contractions a. Isotonic occurs when the muscles contract and shorten (i.e. walk, talk) b. Isometric occurs when the tension in a muscle increases but the muscle does not shorten (i.e. tensing abdominal muscles) Atrophy and hypertrophy If we fail to exercise, our muscles become weak and flaccid; muscles may shrink from disuse which is called atrophy or if we over-exercise, muscles will become enlarged or hypertrophic In hypertrophy, the size of the muscle fiber (cell) enlarges Principle Skeletal Muscles Skeletal or voluntary muscles o Move the skeleton and line the walls of the oral, abdominal and pelvic cavities Also control movement of the eyeballs, eyelids, lips, tongues, and skin Naming of Skeletal Muscles Muscles are named by: a. Location b. Size c. Direction
d. Number of origins e. Location of origin and insertion Not all muscles are named by above method Muscles 656 muscles in the human body 327 antagonistic muscle pairs and two unpaired muscles a. Orbicularis oris b. Diaphragm Muscles can be divided and subdivided into the following Muscle regions a. Head muscles (expression, mastication, tongue, pharynx, soft palate) b. Neck muscles (head, hyoid bone, larynx, upper ribs) c. Trunk and extremity muscles (vertebral column, scapula, breathing, humerus, forearm, wrist, hand, fingers, pelvis, femur, leg, ankle, foot and toes) Muscles of the Head and Neck Control expressions such as anger, fear, grief, joy, pleasure and pain o 1. Frontalis located on either side of the forehead raises eyebrow and wrinkles forehead; controls expression: surprise 2. Orbicularis oculi surrounds the eye orbit underlying the eyebrows and closes the eyelid and tightens the skin on the forehead; controls expression: sadness Mastication (chewing) muscles control the mandible (lower jaw) Movement of the head can cause extension, flexion and rotation Muscles Muscles of the upper extremities a. Shoulder, arm and hand movements 1. Trapezius a large triangular muscle located on the upper surface of the back which moves the shoulder and extends the head 2. Deltoid a thick triangular muscle that covers the shoulder joint which abducts the upper arm 3. Pectoralis major the anterior part of the chest which flexes the upper arm and helps to abduct the upper arm 4. Biceps the upper arm to radius which flexes the lower arm 5. Triceps the posterior arm to ulna or back of upper arm which extends the lower arm Muscles of the trunk a. Breathing and movement of the abdomen and pelvis 1. Rectus abdominis extends from the ribs to the pelvis which compresses the abdomen 2. Internal oblique found directly beneath the external oblique, its fibers running in the opposite direction which depresses ribs, flexes the spinal column and compresses the abdominal cavity 3. Diaphragm a dome-shaped muscle separating the thoracic and abdominal cavities which helps to control breathing Muscles of the lower extremities a. Thigh, leg, ankle, foot, and toes 1. Gluteus maximus muscle forms the buttocks which extends femur and rotates it outward 2. Gastrocnemius calf muscle which points toes and flexes the lower leg 3. Vastus lateralis anterior thigh
4. Soleus a broad flat muscle found beneath the gastrocnemius which extends the foot Exercise Alters the size, structure, and strength of a muscle Size and muscle structure a. Atrophy caused by a lack of muscle use b. Hypertrophy caused by excessive use c. Scar formation from injury 1. Injured muscles can regenerate only to a limited degree 2. Muscle tissue is replaced by connective (scar) tissue when extensive muscle damage occurs Effects of training on muscle efficiency a. Improved coordination b. Improved respiratory and circulatory system c. Elimination or reduction of excess fat d. Improved joint movement Effect of training on muscle strength a. Increase in muscle size b. Improved antagonistic muscle coordination c. Improved functioning in the cortical brain region, where the nerve impulses that start muscular contraction Massage Muscles Massage uses positioning, hands-on pressure, and movement to promote relaxation and to loosen and increase motion in muscles; the health care professional must be aware of the specific skeletal muscles involved in therapeutic massage Potential health benefits a. Improved circulation and blood pressure b. Relieves edema c. Releases stress-reducing hormones d. Fosters faster healing of strains and sprains Electrical Stimulation Passing electrical currents through the skin into the body for therapeutic uses Effect is achieved by stimulating Stimulate nerve tissue o Does not produce heat or cold Used in physical therapy to increase ROM, improve muscle tone, enhance function, pain control, accelerate wound healing and reduce muscle spasm Intramuscular Injections A working knowledge of the major skeletal muscles and the underlying anatomy of the area to be injected is needed Most common sites for IM injection a. Deltoid (upper arm) b. Vastus lateralis (anterior thigh) c. Dorsal gluteal or ventral gluteal (buttocks) Musculoskeletal Disorders Muscular coordination is vital if a person is to perform daily functions efficiently; injuries and diseases, which may affect the musculoskeletal system, sometimes interfere with these functions Muscle atrophy muscles shrink in size and lose muscle strength
o Causes of atrophy include stroke, nerve paralysis, prolonged bed rest or immobilization of a limb in a cast Muscle strain overstretching or tear of a muscle a. Causes of strains include lifting too much weight, lifting improperly or excessive use of a muscle b. Symptoms include soreness, pain and tenderness c. Treat using the RICE method Muscle spasm - cramp or sustained contraction of the muscle which may occur due to overuse Myalgia muscle pain Hernia occurs when an organ protrudes through a weak muscle o 3 types of hernias 1. Abdominal hernia organs protrude through the abdominal wall 2. Inguinal hernia occurs in the inguinal area 3. Hiatal hernia occurs when the stomach pushes through the diaphragm Flatfeet (talipes) results form a weakening of the leg muscles that support the arch Tetanus (lockjaw) infectious disease characterized by continuous spasms of the voluntary muscles Torticollis (wry neck) may be due to an inflammation of the trapezius and/or sternocleidomastoid muscle Muscular dystrophy a group of diseases in which the muscle cells deteriorate Myastenia gravis grave muscle weakness occurs when the connection between the nerves and muscle is lost Recreational Injuries Exercise can sometimes lead to excessive stress on the tendons which attach muscle to bone; tendons are not able to contract and return to their original place therefore more susceptible to straining and tearing Tennis elbow tendon that connects the arm muscle to the elbow becomes inflamed because of the repetitive use of the arm and under conditioning Shin splints injury to the muscle tendon in the front of the shin or tibia Rotator cuff disease an inflammation of a group of tendons that fuse together and surround the shoulder joint caused by repetitive overhead swinging Treatment a. Short term treatment for sprains, tears, pulls and other minor muscle of joint injuries b. RICE 1. R Rest 2. I Ice 3. C Compression 4. E Elevation