Chapter 11: The Muscular System Biol 141 A&P

1. Chapter 11:The Muscular SystemBiol 141 A&P

2. The Muscular System • Consists only of skeletal muscles • How are fascicles arranged in the various types of muscles, and what are the resulting functional differences?

3. Muscle Organization and Function • Muscle organization affects power, range, and speed of muscle movement Fascicles • Muscle cells (fibers) are organized in bundles (fascicles) Classification of Skeletal Muscles • By the way fascicles are organized • By relationships of fascicles to tendons

4. Organization of Skeletal Muscle Fibers • 4 patterns of fascicle organization: • 1) Parallel- • Fibers parallel to the long axis of muscle - e.g., biceps brachii • 2) Convergent- • 3) Pennate- • 4) Circular-

5. Parallel Muscles Figure 11–1a

6. Parallel Muscle Body • The center or body of the muscle thickens when parallel muscle contracts • Parallel muscles contract about 30% Parallel Muscle Tension • Depends on total number of myofibrils • Directly relates to cross section of muscle • 1 in.2 (6.45 cm2) of cross section develops 50 lb (23 kg) of tension

7. Convergent Muscles Figure 11–1b

8. Convergent Muscles • A broad area converges on attachment site (tendon, aponeurosis, or raphe) • Muscle fibers pull in different directions, depending on stimulation • e.g., pectoralis muscles

9. Pennate Muscles Figure 11–1c, d, e

10. Pennate Muscles • Unipennate: • fibers on 1 side of tendon • e.g., extensor digitorum • Bipennate: • fibers on both sides of tendon • e.g., rectus femoris • Multipennate: • tendon branches within muscle • e.g., deltoid

11. Pennate Muscles • Form an angle with the tendon • Do not move as far as parallel muscles • Contain more myofibrils than parallel muscles • Develop more tension than parallel muscles

12. Circular Muscles Figure 11–1f

13. Circular Muscles • Also called sphincters • Open and close to guard entrances of body • e.g., obicularis oris

14. Skeletal Motion • Skeletal muscles attach to skeleton, produce motion • Type of muscle attachment affects power, range, and speed of muscle movement

15. What are the classes of levers, and how do they make muscles more efficient? Levers • Mechanically, each bone is a lever (a rigid, moving structure): • and each joint a fulcrum (a fixed point) • Muscles provide applied force (AF): • required to overcome resistance (R)

16. Functions of a Lever • To change: • direction of an AF • distance and speed of movement produced by an AF • effective strength of an AF

17. 3 Classes of Levers • Depend on the relationship between applied force, fulcrum, and resistance: • first class • second class • third class PLAY First, Second, and Third-Class Levers

18. First-Class Levers Figure 11–2a

19. First-Class Levers • Seesaw is an example • Center fulcrum between applied force and resistance • Force and resistance are balanced

20. Second–Class Levers Figure 11–2b

21. Second-Class Levers • Wheelbarrow is an example • Center resistance between applied force and fulcrum • A small force moves a large weight

22. Third-Class Levers Figure 11–2c

23. Third-Class Levers • Most common levers in the body • Center applied force between resistance and fulcrum • Greater force moves smaller resistance • Maximizes speed and distance traveled

24. KEY CONCEPT • Skeletal muscles can shorten to 70% of resting length • Power, speed, and range of movement • Depend on positions of muscle attachment • Relative to joints

25. How are actions of a muscle based on the relative positions of its origin and insertion?

26. Origins and Insertions • Muscles have 1 fixed point of attachment (origin) and 1 moving point of attachment (insertion) • Most muscles originate or insert on the skeleton • Origin is usually proximal to insertion

27. Actions • Movements produced by muscle contraction • Body movements • e.g., flexion, extension, adduction, etc. • Described in terms of bone, joint, or region

28. How do muscles interact to produce or oppose movements?Muscle Interactions • Muscles work in groups to maximize efficiency • Smaller muscles reach maximum tension first, followed by larger, primary muscles

29. Muscle Terminology Based on Function • Agonist (prime mover): • produces a particular movement • Antagonist: • opposes movement of a particular agonist • Synergist: • a smaller muscle that assists a larger agonist • helps start motion or stabilize origin of agonist (fixator)

30. Muscle Opposition • Agonists and antagonists work in pairs: • when 1 contracts, the other stretches • i.e., flexors–extensors, abductors–adductors, etc.

31. How does the name of a muscle help identify its location, appearance, or function?

32. Names of Skeletal Muscles • Correct names of muscles include the term muscle • Exceptions: • platysma • diaphragm

33. Naming Skeletal Muscles Table 11–1 (1 of 2)

34. Naming Skeletal Muscles Table 11–1 (2 of 2)

35. Descriptive Names for Skeletal Muscles • Location in the body-Identifies body regions: e.g.- temporalis muscle • Origin and insertion- First part of name indicates origin, Second part of name indicates insertion: e.g. genioglossus muscle • Fascicle organization-Describes fascicle orientation within muscle: • i.e.,rectus (straight), transversus, oblique

36. Descriptive Names for Skeletal Muscles 4. Relative position- Externus(superficialis): • visible at body surface • Internus(profundus):deep muscles • Extrinsic:muscles outside an organ • Intrinsic:muscles inside an organ 5. Structural characteristics- Number of tendons: • bi = 2, tri = 3 • Shape: trapezius, deltoid, rhomboid • Size- 6. Action- Movements: e.g., flexor, extensor, retractor • Occupations or habits: e.g., risor = laughter

37. Names for Muscle Size (1 of 2) • Longus = long • Longissimus = longest • Teres = long and round • Brevis = short • Magnus = large • Major = larger • Maximus = largest • Minor = small • Minimus = smallest

38. Axial and Appendicular Muscles Figure 11–3a

39. Axial and Appendicular Muscles Figure 11–3b

40. Divisions of the Muscular System • Axial muscles: • position head and spinal column • move rib cage • 60% of skeletal muscles • Appendicular muscles: • support pectoral and pelvic girdles • support limbs • 40% of skeletal muscles

41. What are the principle axial muscles of the body, their origins, insertions, actions, and innervation?The Axial Muscles • Divisions based on location and function: • muscles of head and neck • muscles of vertebral column • oblique and rectus muscles • muscles of pelvic floor

42. 6 Muscle Groups of the Head and Neck • Muscles of facial expression: • originate on skull • Extrinsic eye muscles: • originate on surface of orbit • control position of eye 3D Peel-Away of Muscles of the Head and Neck PLAY

43. 6 Muscle Groups of the Head and Neck • Muscles of mastication: • move the mandible • Muscles of the tongue: • names end in glossus • Muscles of the pharynx: • begin swallowing process

44. 6 Muscle Groups of the Head and Neck • Anterior muscles of the neck: • control position of larynx • depress the mandible • support tongue and pharynx

45. Muscles of Facial Expression Figure 11–4a

46. Muscles of Facial Expression Figure 11–4b

47. Muscles of Facial Expression • Orbicularis oris: • constricts the mouth opening • Buccinator: • moves food around the cheeks • Muscles of the epicranium (scalp)

48. Muscles of the Epicranium (Scalp) • Temporoparietalis • Occipitofrontalis: • frontal and occipital bellies • separated by epicranial aponeurosis • Platysma: • covers anterior surface of neck

49. Summary: Muscles of Facial Expression Table 11–2 (1 of 2)

50. Summary: Muscles of Facial Expression Table 11–2 (2 of 2)