Understanding the Muscular System: Anatomy, Physiology & Function

2. Chapter 9 The Muscular System

3. Introduction • Skeletal muscles: movement in environment • Smooth muscles: intestines, ureters, veins and arteries • Cardiac muscle: pumps blood through heart and blood vessels • 40–50% of body weight

4. The Types of Muscle

5. The Types of Muscle (cont’d.) • Skeletal: voluntary, striated, and multinucleated • Smooth: involuntary, nonstriated, and uninucleated • Cardiac: involuntary, striated, and uninucleated

6. The Anatomy of Skeletal or Striated Muscle

7. The Anatomy of Skeletal or Striated Muscle (cont’d.) • Skeletal muscle cell surrounded by sarcolemma • Fasciculi: bundles of fascicles • Fascicles: individual bundles of muscle fibers

8. The Anatomy of Skeletal or Striated Muscle (cont’d.) • Perimysium: surrounds each fascicle • Epimysium: covers the perimysium • Fascia: covers the epimysium • Myosin: A bands • Actin: I bands • Z lines • H zone

9. The Anatomy of Skeletal or Striated Muscle (cont’d.) • Sarcomere: between two adjacent Z lines • Actual contraction process occurs here • Sarcotubular system • T system and sarcoplasmic reticulum

10. The Physiology of Muscle Contraction

11. Introduction • Motor unit: all muscle cells innervated by one motor neuron • Muscle cell properties • Excitability • Conductivity • Contractility • Elasticity

12. Neuroelectrical Factors • Na+ higher concentration outside muscle cell • K+ higher concentration inside muscle cell • Resting potential: charge outside positive and inside negative • Electrical potential: rush of Na+ inside cell • K+ moves outside cell attempting to balance

13. Neuroelectrical Factors (cont’d.)

14. Neuroelectrical Factors (cont’d.) • Action potential • Calcium released • Troponin and tropomyosin action inhibited • Activated myosin links to actin filaments

15. Chemical Interactions • Myosin heads contain ATP • ATP releases energy upon myosin/action link • Energy released used to pull action • Sodium: potassium pump pumps out sodium • Resting potential restored

16. Chemical Interactions

17. Energy Sources • ATP: energy source for muscle contraction • ATP production • Glycolysis • Krebs citric acid cycle • Electron transport • Alternate sources: fatty acids and phosphocreatine

18. The Muscle Twitch

19. The Muscle Twitch (cont’d.) • Stimulus > latent period > contraction > relaxation • Contraction strength depends on • Strength, speed, and duration of stimulus • Weight of load • Temperature • All-or-none law

20. The Muscle Twitch (cont’d.)

21. Muscle Tone

22. Muscle Tone (cont’d.) • State of partial contraction throughout whole muscle • Maintains pressure on abdominal contents • Helps maintain blood pressure • Aids digestion • Types • Isotonic, isometric

23. The Anatomy of Smooth Muscle

24. The Anatomy of Smooth Muscle (cont’d.) • Found in hollow structures • Involuntary, uninucleated, nonstriated • Arrangement (two layers) • Longitudinal (outer) • Circular (inner)

25. The Anatomy of Cardiac Muscle

26. The Anatomy of Cardiac Muscle (cont’d.) • Autonomic nervous system control • Involuntary, uninucleated, striated • Intercalated disks: coordinate contraction • Cardiac muscles: contract, relax, and contract 75 times/minute

27. The Naming and Actions of Skeletal Muscles

28. The Naming and Actions of Skeletal Muscles (cont’d.) • Action • Shape • Origin and insertion • Location • Direction of fibers

29. The Naming and Actions of Skeletal Muscles (cont’d.) • Origin: more fixed attachment of muscle • Insertion: movable attachment of muscle • Tendons: attach muscle to bone • Aponeurosis: wide flat tendon

30. The Naming and Actions of Skeletal Muscles (cont’d.) • Flexors: bend limb at a joint • Extensor: straighten limb at a joint • Abductors: move limb away from midline • Adductors: bring limb toward midline • Rotators: revolve limb around axis

31. The Naming and Actions of Skeletal Muscles (cont’d.) • Dorsiflexors: raise the foot • Plantar flexors: lower the foot • Supinators: turn palm upward • Pronators: turn palm downward

32. The Naming and Actions of Skeletal Muscles (cont’d.) • Levators: raise a part of the body • Depressors: lower a part of the body • Prime movers or agonists: bring about an action • Antagonists: oppose agonists • Synergists: assist prime movers

33. The Function and Location of Selected Skeletal Muscles

34. Superficial Muscles • Superficial muscles of the body, anterior view

35. Superficial Muscles (cont’d.) • Superficial muscles of the body, posterior view

36. Muscles of Facial Expression • Occipitalis • Frontalis • Zygomaticus • Levator labii superioris • Orbicularis oris and buccinator

37. Muscles of Facial Expression (cont’d.) • Some muscles of the head and neck, anterior view

38. Muscles of Facial Expression (cont’d.) • Some muscles of the head and neck, lateral view

39. Muscles of Mastication • Masseter • Temporalis • Pterygoid

40. Muscles of the Eye • Superior rectus • Inferior rectus • Medial rectus • Lateral rectus • Superior and inferior oblique

41. Muscles Moving the Head • Sternocleidomastoid • Contraction of both causes flexion of neck • Contraction of one causes rotation to left or right

42. Muscles Moving the Head

43. Muscles Moving the Shoulder Girdle • Levator scapulae • Rhomboids • Pectoralis minor • Trapezius • Serratus anterior

44. Muscles Moving the Humerus • Pectoralis major • Latissimus dorsi • Teres minor • Deltoid • Supraspinatus • Infraspinatus

45. Muscles Moving the Humerus

46. Muscles Moving the Elbow • Brachialis • Biceps brachii • Brachioradialis • Triceps brachii • Anconeus

47. Muscles Moving the Wrist • Flexor carpi • Extensor carpi

48. Muscles Moving the Hand • Supinator • Pronator teres • Pronator quadratus

49. Muscles Moving the Thumb • Flexor pollicis • Extensor pollicis • Adductor pollicis • Abductor pollicis • Opponens pollicis

50. Muscles Moving the Fingers • Flexor digitorum • Extensor digitorum • Interossei