Chapter 7 The Muscular System

1. Chapter 7The Muscular System

2. Muscular System Overview • Muscle: general term for all contractile tissue • Contractile property of muscle tissue allows it to become short and thick as a result of nerve impulse and then to relax once impulse is removed; alternative contraction and relaxation causes movement

3. Muscular System Overview (cont’d) • Cells of muscle tissue are called muscle fibers • Muscle tissue constructed of bundles of these fibers, each approximately the size of a human hair

4. Types of Muscles • Three major types of muscles: • Skeletal • Smooth • Cardiac • Skeletal muscles • Voluntary muscles, attach to bones of skeletal system • Fibers appear striped, so sometimes called striated muscle • Allow external movement and are developed through exercise

5. Types of Muscles (cont’d) • Smooth muscles • Involuntary muscles, called smooth because don’t have striped appearance of skeletal muscles • Found within certain organs, blood vessels, and airways, and allow for internal movement • Change in blood vessel diameter is one example

6. Types of Muscles (cont’d) • Cardiac muscle • Completely involuntary; specialized muscle with striated appearance • Found solely in heart • Contraction of muscle causes heart beat, internal movement

8. Pathology Connection: Myopathy • General term for muscle disease or disorder • Causes include: injury, genetics, nervous system disorders, medication, cellular abnormalities • Symptoms: weakness, cramping, stiffness, spasm • Treatment depends on cause

9. Skeletal Muscles • Attached to bones, provide movement for body • Tendons: fibrous tissues that attach skeletal muscles to bones • Ligaments: attach bone to bone • Some muscles attach directly to bone or soft tissue without tendon

10. Skeletal Muscles • Called voluntary because movement controlled by conscious thought • Responsible for movement and maintaining posture • Also generate heat

12. Pathology Connection: Strains and Tears • Strains caused by overstretching tendons or muscles • Severity of injury can range from mild to severe • Mild: pulled muscle (slight overstretch of muscle) • Severe: complete muscle tear or complete tendon rupture

13. Pathology Connection: Strains and Tears (cont’d) • Injuries can be acute or chronic • Acute: usually resulting from trauma • Chronic: usually resulting from overuse or disease

14. Pathology Connection: Strains and Tears (cont’d) • Signs and symptoms: vary depending on severity of injury • Mild strain (no tear of muscle or tendon fibers): mild pain and possibly stiffness • Moderate strain (some tearing of muscle or tendon fibers): more intense pain, bruising, obvious weakness • Severe strain (complete tear of muscle or tendon): severe pain, swelling, extensive bruising, and often complete loss of movement

15. Pathology Connection: Strains and Tears (cont’d) • Diagnosis: medical history, physical examination, imaging (MRI, X-ray, ultrasound)

16. Pathology Connection: Strains and Tears (cont’d) • Treatment: varies with severity of injury • Strains • In first 72 hours, PRICE therapy: Protection, Rest, Ice, Compression, Elevation • After first 72 hours: gradual increase in activity and/or physical therapy, application of heat • Pain relievers (like acetaminophen or ibuprofen)

17. Pathology Connection: Strains and Tears (cont’d) • Tears: treated surgically at time of diagnosis • Strains are often slow to heal • Skeletal muscle and dense regular connective tissue have only moderate ability to repair themselves

18. Pathology Connection: Tendinitis/Tendinosis • Cause • Degenerative disease leading to breakdown and scarring of tendons • Appears to be caused by failure of tendons to repair themselves after injury • Commonly seen related to overuse/ repetitive motion or untreated acute injuries

19. Pathology Connection: Tendinitis/Tendinosis(cont’d) • Risk factors • Some tendons more prone to tendinosis • Rotator cuff • Achilles tendon • Tibialis posterior tendon • Tendons of lateral elbow

20. Pathology Connection: Tendinitis/Tendinosis(cont’d) • Risk factors • Other risk factors • Age • Gender • Skeletal anatomy • Types of occupational equipment used • Systemic disease (like diabetes mellitus, because of poor wound healing

21. Pathology Connection: Tendinitis/Tendinosis(cont’d) • Signs and symptoms include pain, tenderness, and stiffness

22. Pathology Connection: Tendinitis/Tendinosis(cont’d) • Treatment types • PRICE • Physical therapy • Steroids (short term only) • Lasers • Ultrasound and extracoporeal shock wave therapy • Surgery is a last resort • Unfortunately, treatments not very effective, prognosis not as good as for acute tendon injuries

24. Figure 7-4Skeletal muscles of the posterior and anterior trunk.

28. Pathology Connection: Fibromyalgia Syndrome • Myalgia: pain or tenderness in muscle • Fibromyalgia Syndrome: chronic pain syndrome • Epidemiology: more common in women

29. Pathology Connection:Fibromyalgia Syndrome • Characterized by • Pain of three months duration • Bilateral tenderness • Fatigue • Sleep disorders • Depression • Anxiety • Exercise intolerance

30. Pathology Connection:Fibromyalgia Syndrome (cont’d) • Cause: unknown • There does not seem to be any inflammation involved • May be caused by hyperactive stress response • May also be caused by sensory or neurological problem leading to an increased sensitivity to pain • Diagnosis: pain in 11 of 18 designated tender points for fibromyalgia

31. Pathology Connection:Fibromyalgia Syndrome (cont’d) • Treatment • No definitive treatment • Symptoms can be managed with antidepressants, antiepileptics, exercise, and/or pain relievers • Symptom management often inadequate at relieving pain completely

32. Contraction and Relaxation • Movement of body is result of contraction (shortening) of certain muscles while there is relaxation of others • Primary mover (or agonist) is chief muscle causing movement; as muscle contracts it pulls bone, causing movement • Point of origin: muscle end attached to stationary bone • Point of insertion: muscle end attached to moving bone

34. Contraction and Relaxation (cont’d) • Synergistic muscles assist primary mover • Antagonist muscles cause movement in opposite direction of agonist • All movement is result of contraction of primary movers and relaxation of opposing muscles

35. Contraction and Relaxation (cont’d) • Diaphragm: primary mover of breathing • Dome shaped muscle separates abdominal cavity from thoracic cavity, responsible for performing major work of bringing atmospheric air into lungs • Muscle is under both voluntary and involuntary control

39. Functional Unit of the Muscle • Each muscle cell is elongated fiber known as muscle fiber, can be up to 12 inches in length • Several muscle fibers can be bundled together to form specific muscle segment • Each muscle fiber composed of several myofibrils

40. Functional Unit of the Muscle (cont’d) • Sarcomeres: functional contractile units of each fiber • Each has two types of threadlike structures called thick and thin myofilaments • Thick myofilaments made up of protein myosin • Thin myofilaments made up of protein actin

41. Functional Unit of the Muscle (cont’d) • Sarcomeres: functional contractile units of each fiber • Sarcomere has actin and myosin filaments arranged in repeating units separated from each other by dark bands called Z lines which give striated appearance to skeletal muscle • Z lines are borders of each sarcomere

42. Functional Unit of the Muscle (cont’d) • Contraction of muscle causes two types of myofilaments to slide toward each other and shorten each sarcomere, and therefore entire muscle • Muscle contraction requires temporary connections of cross-bridges formed between myosin head and actin; these pull sarcomere together

45. ATP and Calcium • Energy needed for contraction and relaxation; comes from adenosine triphosphate (ATP), which help myosin heads form and break cross-bridges with actin • Calcium stored away from actin and myosin in sarcoplasmic reticulum (SR) during relaxation of muscle

46. ATP and Calcium (cont’d) • During contraction, calcium released from SR and causes actin, myosin, and ATP to interact, which causes contraction; when calcium leaves muscle and returns to SR, cross-bridge attachments are broken and muscle relaxes

47. ATP and Calcium (cont’d) • When nervous system tells muscle to contract, signal causes muscle fiber to open sodium ion channels • Sodium ions flow into muscle fiber, exciting it • When muscle becomes excited, calcium released from SR • It is calcium that causes muscles to contract • Calcium is then pumped back into SR

48. Pathology Connection: Tetanus • Also called “Lock Jaw;” caused by untreated bacterial wound infection • Bacteria responsible is Clostridium tetani, which lives in soil • Bacteria produces toxin that causes disease

49. Pathology Connection: Tetanus (cont’d) • Signs and symptoms • Muscle spasms (involuntary, sudden and violent muscle contractions); may be triggered by minor stimuli (like loud noises, turning on a light) • Rigid paralysis • Stiffness • Pain

50. Pathology Connection: Tetanus (cont’d) • Course of disease: symptoms usually begin in jaw, progress over time; eventually, diaphragm may become paralyzed • Treatment • Cleaning of wound • Injection of IV tetanus anti-toxin • Sedation • Ventilator support • Pain management