1. Muscle Tissue A primary tissue type, divided into: A primary tissue type, divided into: –skeletal muscle –cardiac muscle –smooth muscle

2. Skeletal Muscles Are attached to the skeletal system Are attached to the skeletal system Allow us to move Allow us to move

3. The Muscular System Includes only skeletal muscles Includes only skeletal muscles

4. Skeletal Muscle Structures Muscle tissue (muscle cells or fibers) Muscle tissue (muscle cells or fibers) Connective tissues Connective tissues Nerves Nerves Blood vessels Blood vessels

5. Functions of Skeletal Muscles 1. Produce skeletal movement 2. Maintain body position 3. Support soft tissues 4. Guard body openings 5. Maintain body temperature

6. Organization of Connective Tissues Figure 10–1

7. Epimysium Exterior collagen layer Exterior collagen layer Connected to deep fascia Connected to deep fascia Separates muscle from surrounding tissues Separates muscle from surrounding tissues

8. Perimysium Surrounds muscle fiber bundles (fascicles) Surrounds muscle fiber bundles (fascicles) Contains blood vessel and nerve supply to fascicles Contains blood vessel and nerve supply to fascicles

9. Endomysium Surrounds individual muscle cells (muscle fibers) Surrounds individual muscle cells (muscle fibers) Contains capillaries and nerve fibers contacting muscle cells Contains capillaries and nerve fibers contacting muscle cells Contains satellite cells (stem cells) that repair damage Contains satellite cells (stem cells) that repair damage

10. Muscle Attachments Endomysium, perimysium, and epimysium come together: Endomysium, perimysium, and epimysium come together: –at ends of muscles –to form connective tissue attachment to bone matrix –i.e., tendon (bundle) or aponeurosis (sheet)

11. Nerves Skeletal muscles are voluntary muscles, controlled by nerves of the central nervous system Skeletal muscles are voluntary muscles, controlled by nerves of the central nervous system

12. Blood Vessels Muscles have extensive vascular systems that: Muscles have extensive vascular systems that: –supply large amounts of oxygen –supply nutrients –carry away wastes

13. Formation of Skeletal Muscle Fibers Skeletal muscle cells are called fibers Skeletal muscle cells are called fibers Figure 10–2

14. Skeletal Muscle Fibers Are very long Are very long Develop through fusion of mesodermal cells (myoblasts) Develop through fusion of mesodermal cells (myoblasts) Become very large Become very large Contain hundreds of nuclei Contain hundreds of nuclei

15. Organization of Skeletal Muscle Fibers Figure 10–3

16. The Sarcolemma The cell membrane of a muscle cell The cell membrane of a muscle cell Surrounds the sarcoplasm (cytoplasm of muscle fiber) Surrounds the sarcoplasm (cytoplasm of muscle fiber) A change in transmembrane potential begins contractions A change in transmembrane potential begins contractions

17. Transverse Tubules (T tubules) Transmit action potential through cell Transmit action potential through cell Allow entire muscle fiber to contract simulataneously Allow entire muscle fiber to contract simulataneously Have same properties as sarcolemma Have same properties as sarcolemma

18. Myofibrils Lengthwise subdivisions within muscle fiber Lengthwise subdivisions within muscle fiber Made up of bundles of protein filaments (myofilaments) Made up of bundles of protein filaments (myofilaments) Myofilaments are responsible for muscle contraction Myofilaments are responsible for muscle contraction

19. Types of Myofilaments Thin filaments: Thin filaments: –made of the protein actin Thick filaments: Thick filaments: –made of the protein myosin

20. Sarcoplasmic Reticulum A membranous structure surrounding each myofibril A membranous structure surrounding each myofibril Helps transmit action potential to myofibril Helps transmit action potential to myofibril Similar in structure to smooth endoplasmic reticulum Similar in structure to smooth endoplasmic reticulum Forms chambers (terminal cisternae) attached to T tubules Forms chambers (terminal cisternae) attached to T tubules

21. A Triad Is formed by 1 T tubule and 2 terminal cisternae Is formed by 1 T tubule and 2 terminal cisternae

22. Cisternae Concentrate Ca 2+ (via ion pumps) Concentrate Ca 2+ (via ion pumps) Release Ca 2+ into sarcomeres to begin muscle contraction Release Ca 2+ into sarcomeres to begin muscle contraction

23. Sarcomeres Figure 10–4

24. Sarcomeres The contractile units of muscle The contractile units of muscle Structural units of myofibrils Structural units of myofibrils Form visible patterns within myofibrils Form visible patterns within myofibrils

25. Muscle Striations A striped or striated pattern within myofibrils: A striped or striated pattern within myofibrils: –alternating dark, thick filaments (A bands) and light, thin filaments (I bands)

26. M Lines and Z Lines M line: M line: –the center of the A band –at midline of sarcomere Z lines: Z lines: –the centers of the I bands –at 2 ends of sarcomere

27. Zone of Overlap The densest, darkest area on a light micrograph The densest, darkest area on a light micrograph Where thick and thin filaments overlap Where thick and thin filaments overlap

28. The H Zone The area around the M line The area around the M line Has thick filaments but no thin filaments Has thick filaments but no thin filaments

29. Titin Are strands of protein Are strands of protein Reach from tips of thick filaments to the Z line Reach from tips of thick filaments to the Z line Stabilize the filaments Stabilize the filaments

30. Sarcomere Structure Figure 10–5

31. Sarcomere Function Transverse tubules encircle the sarcomere near zones of overlap Transverse tubules encircle the sarcomere near zones of overlap Ca 2+ released by SR causes thin and thick filaments to interact Ca 2+ released by SR causes thin and thick filaments to interact

32. Figure 10–6 (1 of 5) Level 1: Skeletal Muscle

33. Level 2: Muscle Fascicle Figure 10–6 (2 of 5)

34. Level 3: Muscle Fiber Figure 10–6 (3 of 5)

35. Level 4: Myofibril Figure 10–6 (4 of 5)

36. Level 5: Sarcomere Figure 10–6 (5 of 5)

37. A Thin Filament Figure 10–7a

38. 4 Thin Filament Proteins 1. F actin: –is 2 twisted rows of globular G actin –the active sites on G actin strands bind to myosin

39. 4 Thin Filament Proteins 2. Nebulin: –holds F actin strands together

40. 4 Thin Filament Proteins 3. Tropomyosin: –is a double strand –prevents actin–myosin interaction

41. 4 Thin Filament Proteins 4. Troponin: –a globular protein –binds tropomyosin to G actin –controlled by Ca 2+

42. Troponin and Tropomyosin Figure 10–7b

43. Initiating Contraction Ca 2+ binds to receptor on troponin molecule Ca 2+ binds to receptor on troponin molecule Troponin–tropomyosin complex changes Troponin–tropomyosin complex changes Exposes active site of F actin Exposes active site of F actin

44. A Thick Filament Figure 10–7c

45. Thick Filaments Contain twisted myosin subunits Contain twisted myosin subunits Contain titin strands that recoil after stretching Contain titin strands that recoil after stretching

46. The Mysosin Molecule Figure 10–7d

47. The Mysosin Molecule Tail: Tail: –binds to other myosin molecules Head: Head: –made of 2 globular protein subunits –reaches the nearest thin filament

48. Mysosin Action During contraction, myosin heads: During contraction, myosin heads: –interact with actin filaments, forming cross- bridges –pivot, producing motion

49. Sliding Filaments Figure 10–8

50. Skeletal Muscle Contraction Sliding filament theory: Sliding filament theory: –thin filaments of sarcomere slide toward M line –between thick filaments –the width of A zone stays the same –Z lines move closer together InterActive Physiology: Sliding Filament Theory PLAY

51. Skeletal Muscle Contraction Figure 10–9 (Navigator)

52. Skeletal Muscle Innervation Figure 10–10a, b (Navigator)

53. Skeletal Muscle Innervation Figure 10–10c

54. The Neuromuscular Junction Is the location of neural stimulation Is the location of neural stimulation Action potential (electrical signal): Action potential (electrical signal): –travels along nerve axon –ends at synaptic terminal

55. Synaptic Terminal Releases neurotransmitter (acetylcholine or ACh) Releases neurotransmitter (acetylcholine or ACh) Into the synaptic cleft (gap between synaptic terminal and motor end plate) Into the synaptic cleft (gap between synaptic terminal and motor end plate)

56. The Neurotransmitter Acetylcholine or ACh: Acetylcholine or ACh: –travels across the synaptic cleft –binds to membrane receptors on sarcolemma (motor end plate) –causes sodium–ion rush into sarcoplasm –is quickly broken down by enzyme (acetylcholinesterase or AChE)

57. Action Potential Generated by increase in sodium ions in sarcolemma Generated by increase in sodium ions in sarcolemma Travels along the T tubules Travels along the T tubules Leads to excitation–contraction coupling Leads to excitation–contraction coupling