(Students: Bolded, italicized, and underlined sections will be on the exam) The Muscular System: I. Function of the System: A. The primary functions of this system are to support the skeleton, provide skeletal movement, control the digestive system, pump blood, regulate body heat, and to protect soft tissue. II. The Main Parts of the System: Overview of the System and Parts: There are more than 640 muscles in the body, which together account for about 40 percent of a person's weight.. They are the part of our body that allow us to move. They are made up of special tissues that can contract, or shorten, when they receive a signal from the brain. The muscles are attached to bones by stretchy tissue called tendons. When the muscles contract, they pull on the tendons which pull on the bones and cause our limbs to move. Muscles hardly ever work alone. Muscles can get shorter and pull, but they cannot push. So most muscles are arranged in opposing teams. One team pulls the body part one way, then the other team pulls it back again. As each team pulls, the other team relaxes and gets stretched. Muscles band together to form muscle groups which work together. Voluntary muscles, such as your arms and legs can be controlled by your thoughts. All this muscle action is controlled by your brain, which sends and receives signals through your nervous system. ! Muscle actions can be voluntary or involuntary. Involuntary muscles, such as the heart, diaphragm and intestines, are automatically controlled by the brain. You don't have to think about making them work. For example the heart beats between 60 and 80 beats every minute without you having to think about it. The 3 Main Types of Muscle Tissue: In the body, there are three types of muscle: skeletal (striated), smooth, and cardiac. A. Skeletal Muscle: Skeletal muscles provide skeletal movement, controls the entrances and exits of the digestive tract (sphincter muscles), produce heat, and protects bones and soft tissue. They are attached to bones by tendons, and work in flexor/extensor pairs that either contract or relax to create bone movement. Skeletal muscles regulate body temperature by small contractions of the muscle tissue; the friction of the cells within the tissue help to create warmth. Skeletal muscle tissues help to protect the bones and internal organs, such as the digestive organs in the abdomen. The peripheral portion of the central nervous system (CNS) controls the skeletal muscles. Thus, these muscles are under conscious, or voluntary, control. Within the skeletal muscle system there are two types of muscles, axial muscles support and position the axial skeleton. The appendicular muscles support, move and brace limbs. The basic unit is the muscle fiber with many nuclei. These muscle fibers are striated (having transverse streaks) and each acts independently of neighboring muscle fibers. B. Smooth Muscle: Smooth muscle, found in the walls of the hollow internal organs such as blood vessels, the digestive tract, bladder, and uterus, is under control of the autonomic nervous system. This means that it cannot be controlled consciously and thus acts involuntarily. The non-striated (smooth) muscle cell is spindle-shaped and has one central nucleus. Smooth muscle contracts slowly and rhythmically. C. Cardiac Muscle: Cardiac muscle, found in the walls of the heart that pumps blood throughout the body, is also under control of the autonomic nervous system. The cardiac muscle cell has one central nucleus, like smooth muscle, but it also is striated, like skeletal muscle. The cardiac muscle cell is rectangular in shape. The contraction of cardiac muscle is involuntary, strong, and rhythmical. Some Major Groups of Skeletal Muscles: Muscle Fibers: The muscular system is composed of specialized cells called muscle fibers. Their predominant function is contractibility. Muscles, where attached to bones or internal organs and blood vessels, are responsible for movement. Nearly all movement in the body is the result of muscle contraction. Exceptions to this are the action of cilia, the flagellum on sperm cells, and amoeboid movement of some white blood cells. Additional Information About Skeletal Muscles: The integrated action of joints, bones, and skeletal muscles produces obvious movements such as walking and running. Skeletal muscles also produce more subtle movements that result in various facial expressions, eye movements, and respiration. Almost all skeletal muscles either originate or insert on the skeleton producing various forms of movement: flexion, extension, adduction, abduction, protraction, retraction, elevation, depression, rotation, circumduction, pronation, supination, inversion, or eversion. In addition to movement, muscle contraction also fulfills some other important functions in the body, such as posture, joint stability, and heat production. Posture, such as sitting and standing, is maintained as a result of muscle contraction. The skeletal muscles are continually making fine adjustments that hold the body in stationary positions. The tendons of many muscles extend over joints and in this way contribute to joint stability. This is particularly evident in the knee and shoulder joints, where muscle tendons are a major factor in stabilizing the joint. Heat production, to maintain body temperature, is an important by-product of muscle metabolism. Nearly 85 percent of the heat produced in the body is the result of muscle contraction. A whole skeletal muscle is considered an organ of the muscular system. Each organ or muscle consists of skeletal muscle tissue, connective tissue, nerve tissue, and blood or vascular tissue. Skeletal muscles vary considerably in size, shape, and arrangement of fibers. They range from extremely tiny strands such as the stapedium muscle of the middle ear to largest mass of muscle tissue, the Gluteous Maximus in the buttocks and thigh. Some skeletal muscles are broad in shape and some narrow. In some muscles the fibers are parallel to the long axis of the muscle, in some they converge to a narrow attachment, and in some they are oblique. Each skeletal muscle fiber is a single cylindrical muscle cell. An individual skeletal muscle may be made up of hundreds, or even thousands, of muscle fibers bundled together and wrapped in a connective tissue covering. Each muscle is surrounded by a connective tissue sheath called the epimysium. Fascia, connective tissue outside the epimysium, surrounds and separates the muscles. Portions of the epimysium project inward to divide the muscle into compartments. Each compartment contains a bundle of muscle fibers. Each bundle of muscle fiber is called a fasciculus and is surrounded by a layer of connective tissue called the perimysium. Within the fasciculus, each individual muscle cell, called a muscle fiber, is surrounded by connective tissue called the endomysium. Skeletal muscle cells (fibers), like other body cells, are soft and fragile. The connective tissue covering furnish support and protection for the delicate cells and allow them to withstand the forces of contraction. The coverings also provide pathways for the passage of blood vessels and nerves. Commonly, the epimysium, perimysium, and endomysium extend beyond the fleshy part of the muscle, the belly or gaster, to form a thick ropelike tendon or a broad, flat sheet-like aponeurosis. The tendon and aponeurosis form indirect attachments from muscles to the periosteum of bones or to the connective tissue of other muscles. Typically a muscle spans a joint and is attached to bones by tendons at both ends. One of the bones remains relatively fixed or stable while the other end moves as a result of muscle contraction. Skeletal muscles have an abundant supply of blood vessels and nerves. This is directly related to the primary function of skeletal muscle, contraction. Before a skeletal muscle fiber can contract, it has to receive an impulse from a nerve cell. Generally, an artery and at least one vein accompany each nerve that penetrates the epimysium of a skeletal muscle. Branches of the nerve and blood vessels follow the connective tissue components of the muscle of a nerve cell and with one or more minute blood vessels called capillaries. Most skeletal muscles have names that describe some feature of the muscle. Often several criteria are combined into one name. Associating the muscle's characteristics with its name will help you learn and remember them. The following are some terms relating to muscle features that are used in naming muscles. *Size: vastus (huge); maximus (large); longus (long); minimus (small); brevis (short). *Shape: deltoid (triangular); rhomboid (like a rhombus with equal and parallel sides); latissimus (wide); teres (round); trapezius (like a trapezoid, a four-sided figure with two sides parallel). *Direction of fibers: rectus (straight); transverse (across); oblique (diagonally); orbicularis (circular). *Location: pectoralis (chest); gluteus (buttock or rump); brachii (arm); supra(above); infra- (below); sub- (under or beneath); lateralis (lateral). *Number of origins: biceps (two heads); triceps (three heads); quadriceps (four heads). *Origin and insertion: sternocleidomastoideus (origin on the sternum and clavicle, insertion on the mastoid process); brachioradialis (origin on the brachium or arm, insertion on the radius). *Action: abductor (to abduct a structure); adductor (to adduct a structure); flexor (to flex a structure); extensor (to extend a structure); levator (to lift or elevate a structure); masseter (a chewer). III. Interactions With Other Systems: The muscle system interacts with every system, since it helps to protect all of the intermal organs. Also, it helps to regulate body temperate throughout the body. Some examples of systems that directly interact with the system include: • The Nervous System: The nervous system controls the muscles. • The Circulatory System: The heart is made of cardiac muscle tissue. • The Digestive System: The hollow tract of the digestive system is made of smooth muscle tissue. Also, skeletal muscle tissue controls the entrances and exits of the major organs (sphincter muscles). • The Lymphatic System: Lymph is moved throughout the body tissue by movement of the muscle tissue. IV. Some Disease and Disorders: • Arthritis: Arthritis is not a single disease. Over 170 types of arthritis exist. The name which means "inflammation of the joint" is a misnomer since the joint is not inflamed in all types of arthritis. Arthritis is a disease which can greatly impact quality of life and is potentially disabling. It is often caused by ‘old age’ and ‘not moving around’. Arthritis sufferers can take inflammatory drugs to help alleviate the pain, however, there is no cure. • Muscle Strains: Muscle strains or ruptures can occur in the back just like they can anywhere else in the body. A muscle strain (or tear) in the back is usually caused by a sudden movement or trying to lift something that is too heavy. The injury however is often a long time coming on as the muscles in the back gradually tighten up due to bad posture and overuse. These muscles go into spasm and do not get enough blood through them resulting in weakness. So when someone complains they bent down to pick up a piece of paper and tore a muscle in the back, it is not just the piece of paper that caused it but a gradual build up of tension over weeks and months. • Muscle Contusion: If you have suffered a direct blow to a muscle, particularly one near a bone then you must treat it as a contusion. Symptoms include: • A sudden sharp pain in the back. • Possibly swelling or bruising over the area of the rupture. • Difficulty in moving - bending forwards, sideways or straightening. • Muscle Tears: Muscle tears are graded 1, 2 or 3 depending on how bad the tear is. Grade 1: Symptoms: Tightness in the back; may be able to walk properly; probably won't have much swelling. Treatment: See a sports injury professional or therapist who specialises in back problems; use a heat retainer until you feel no pain; ease down training for a week or two but no need to stop unless there is getting pain; use sports massage techniques to speed up recovery (very important); use joint manipulation techniques; use ultrasound and electrical stimulation; rehabilitation and strengthening program; use a lumbar heat retainer. Grade 2: Symptoms: Probably cannot walk properly; may get occasional sudden twinges of pain during activity; may notice swelling; pressing in causes pain. Treatment: Rest; see a sports injury professional for rehabilitation advice; use sports massage techniques to speed up recovery (very important); use ultrasound and electrical stimulation; prescribe a rehabilitation programme of mobility, stretching and strengthening exercises. Grade 3: Symptoms: Unable to walk properly; severe pain; bad swelling appearing immediately; static muscle contraction will be painful and might produce a bulge in the muscle; expect to recovery of 3 to twelve weeks or more. Treatment: Seek medical attention immediately; R.I.C.E. (Rest, Ice, Compress, Elevate.); use crutches; follow a rehabilitation plan as directed by the sports therapist; use sports massage techniques to speed up recovery (very important); apply joint manipulation techniques; use ultrasound and electrical stimulation; go on a rehabilitation program. If the victim suspects a grade two or three injury it is recommend they should see a Sports Injury or back Specialist immediately. Muscular Dystrophy: Muscular dystrophy is the name given to a large number of medical conditions where there is a progressive weakening and wasting of muscles. Cause: The main cause is genetic. They are usually inherited from a parent or parents through their genes, but sometimes appear out of the blue. They affect babies, children, young people and adults of any race. About one in every 2,000 people in the US will have an nmd, but the effects are much wider than that. Relatives may be carrying the faulty genes while not showing any symptoms. That is why so much research has already gone into finding which genes are at fault and how they might be repaired. The genetic risks vary. In some types of nmd both the father and mother must have a faulty gene to pass it on. This is called recessive inheritance. In other types, it only needs one parent to pass on a faulty gene. This is called dominant inheritance. In Duchenne md the mother usually passes the faulty gene on to her son. This is called x-linked inheritance. Progress in research means that once one member of a family is diagnosed it may be possible to test other relatives to detect carriers, or to carry out a "family study". Not all conditions are inherited however. Some conditions are autoimmune. That means the immune system turns inwards to attack targets within the body rather than fighting off external dangers. And there can be a new mutation (or change) in the genes that causes types of nmd to appear for no apparent reason. Symptoms: Some nmds are life-threatening. Others may be very disabling or merely cause a mild disability. Symptoms do not always appear straight away. Muscular dystrophy is mainly progressive. The signs may become more obvious over time. Some symptoms will not show until adulthood. Progress in genetic counselling and diagnosis however is making it much easier to predict which family members may develop the condition over time. The main characteristic of md is a progressive weakening of muscles. Other parts of the body can also be affected however. Cataracts (a clouding in the eye's lens) are common in myotonic dystrophy for example. The heart can be affected in several types of md, whether the individual has the condition or is a carrier. Linked symptoms like this provide another reason for ensuring accurate diagnosis by specialists. Cure: There is, as yet, no cure, but there are ways of treating the symptoms of some conditions (like myotonia congenita) and there is much that can be done practically to improve life for those affected. Muscular dystrophy and other neuromuscular conditions Conditions now classed as muscular dystrophy ¥ Duchenne md ¥ Becker md ¥ Emery-Dreifuss dystrophy ¥ congenital md ¥ limb girdle md (several types) ¥ facioscapulohumeral dystrophy (FSH) ¥ scapulohumeral dystrophy ¥ autosomal recessive childhood dystrophy (like Duchenne md and Becker md) ¥ ocular md ¥ oculopharyngeal md ¥ myotonic dystrophy Related neuromuscular conditions include ¥ spinal muscular atrophy (more than one type) ¥ Charcot Marie Tooth disease also known as hereditary motor sensory neuropathy (HMSN) ¥ autoimmune myopathies ¥ myotonic disorders ¥ myasthenia gravis