Musculoskeletal System

1. Musculoskeletal System Chapter 36 Structural Support and Movement

2. Muscular System • Muscle cells have the capacity to contract • Produces skeletal movement • Maintains posture • Heat generation • Pumps blood through circulatory system • Moves food through digestive tract

3. Muscles • All muscles contract = active • And lengthen = passive

4. 3 Types of Muscle • Skeletal • Cardiac • Smooth

5. Skeletal Muscle • Attached to bones, muscles, or skin • Voluntary movement • Cell structure • Long and cylindrical • Multiple nuclei per cell • Heavily striated • Stimulated by nervous system

6. Cardiac Muscle • Makes up wall of heart • Involuntary movement • Cell structure • Branching interconnections • Single, central nucleus • Striated • Have intercalated discs • Stimulated by electrical impulses, nervous stimuli, hormones Can stimulate its own contraction!

7. Smooth Muscle • Makes up walls of hollow body organs, respiratory passageways, large blood vessels • Involuntary movement • Cell structure • Tapered ends • Single, central nucleus • No visible bands (striations) • Stimulated by nerve impulses, hormones, stretching • Contractions either slow and sustained or slow and wavelike

8. Skeletal Muscle Cell Structure • Tendons attach muscle to bone • Individual muscles cells also called muscle fibers can be large • Multinucleated • Each muscle fiber consists of many myofibrils

9. Myofibrils • Contractile elements composed of actin and myosin proteins • Give muscle striated appearance

10. Myofibrils • Composed of subunits called sarcomeres connected by Z lines • Actin forms thin filaments • Myosin forms thick filaments • Thick myosin filaments bind temporarily to thin actin filaments • Slide past each other shortening the sarcomere and producing muscle contraction

11. Actin and Myosin

12. Skeletal Muscle Contraction

13. Muscle Contraction

14. Muscle requires ATP (adenosine triphosphate), the body’s energy currency

15. Skeletal Muscle Cells in Action • Motor unitis a single neuron and all the muscle fibers it stimulates • A synapseis the place where the neuron meets the muscle cell • Place of communication • In skeletal muscle it is called the neuromuscular junction • The neurotransmitter acetylcholineis the chemical released by the neuron to stimulate the muscle cell

16. Motor Unit Neuron Neuromuscular junction Myofibrils

17. Motor Unit

18. Oxygen Consumption • Aerobic glucose metabolism • Anaerobic glucose metabolism • Inefficient production • Lactic acid accumulation • Oxygen debt • Recovery oxygen consumption

19. Does this guy have more muscle cells than you?

20. Fast Twitch/Low Twitch - it’s in your genes • Fast twitch • Contract quickly and powerfully • Smaller blood supply • Fewer mitochondria • Better adapted to use glycolysis (no O2 required) • Low twitch • Contract more slowly • Abundant mitochondria • High blood supply • Large O2 supply Sprinter Marathon runners

21. Skeleton = supporting framework for the body

22. 3 types of skeletons found in animals • Hydrostatic skeletons • Made of fluid • Exoskeletons • On the outside of the body • Endoskeletons • Within the body

23. Hydrostatic Skeletons • Worms, mollusks, cnidarians • Consist of a fluid filled sac that can’t be compressed • Rely on two layers of muscle in the body wall • One circular, one longitudinal • Movement of a worm • Circular muscles contract – worm appears thin • Longitudinal muscles contract – worm appears thicker

24. Exoskeletons • Means “outside skeleton” • Found on bodies of arthropods (includes insects, spiders, crustaceans) • Are thin and flexible at the joints • Allow complex movements • i.e. web-spinning spiders

25. Endoskeletons • Internal skeleton • Found in echinoderms and chordates (e.g. humans and other vertebrates) • Least common type of skeleton

26. Antagonistic Muscles • Despite the type of skeleton, all animals move by contractions of antagonistic muscles or muscles that work in opposition to one another. • Ex. Flexors and Extensors • Ex. Biceps and triceps

27. Skeletal Function • Provides rigid framework that supports the body and protects internal organs • Brain and spinal cord enclosed within skull and vertebral column • Lungs and heart protected by rib cage • Pelvic girdle protects abdominal organs • Allows for movement • Produces red blood cells, white blood cells, and platelets in the bone marrow of certain bones • Storage for calcium and phosphorous • Sensory transduction – tiny bones of the middle ear • Transmit sound vibrations between the eardrum and the cochlea

28. Skeleton • 206 bones • Axial Skeleton (yellow) • Trunk and skull • Appendicular Skeleton (blue) • Limbs • Pectoral girdle • Pelvic girdle

30. Skeletal Tissue • Connective tissue • All 3 embedded in matrix of collagen • Bone • Cartilage • Ligaments • Attach bone to bone

31. Cartilage • Cartilage • Thick, nonliving matrix • Matrix composed of collagen which is produced by the cartilage cells called Chondrocytes • Flexible and resilient • Shock absorbers • Covers ends of long bones, forms framework for respiratory passages, supports ears and nose, spinal discs, knee joint • Skeletons of some animals are composed of cartilage during early development • Cartilaginous fish (i.e. sharks) have cartilaginous skeletons

32. Cartilage Chondrocytes Collagen matrix

33. Bone • Most rigid form of connective tissue • Collagen fibers hardened by deposits of calcium phosphate • Long bones (i.e. arm and leg bones) contain spongy bone and compact bone

34. Compact Bone • Hard and dense • Makes up main shaft of long bones • Outer layer of other bones • Each ring-like unit with the central canal make up an osteon

35. Spongy Bone • Also called cancellous bone • Has more spaces than compact bone • Found at the ends of long bones and the center of other bones • Made of meshwork of small, bony plates filled with red marrow where blood cells form

36. Bone Remodeling • Allows skeleton to alter its shape in response to demands placed on it. • More you use certain bones, the thicker and stronger they will become

37. Osteoporosis

38. Joints • Hinge joint • Located in elbows, knees, and fingers • Movement in only 2 directions • Ball and socket joint • Ex. Hip and shoulder • Round end of one bone fits into depression of another • Movement in several directions

39. Three Types of Joints

40. Origin and Insertion of a Muscle • Origin • End of muscle that is fixed to bone by a tendon that remains stationary • Insertion • Other end of muscle that is attached to bone on the other side of a joint which is moved by the muscle • Ex. Biceps muscle