1. Chapter 6 The Muscular System
Essentials of Human Anatomy & Physiology
Seventh Edition
Elaine N. Marieb
Chapter 6 The Muscular System
Slides 6.1 – 6.17
Lecture Slides in PowerPoint by Jerry L. Cook
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

2. The Muscular System
Muscles are responsible for all types of body movement
Three basic muscle types are found in the body
Skeletal muscle
Cardiac muscle
Smooth muscle
Slide 6.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

3. Characteristics of Muscles
Skeletal and smooth muscle cells are elongated
(muscle cell = muscle fiber)
Contraction of muscles is due to the movement of microfilaments
All muscles share some terminology
Prefix myo refers to muscle
Prefix mys refers to muscle
Prefix sarco refers to flesh
Slide 6.2
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

4. Skeletal Muscle Characteristics
Most are attached by tendons to bones
Cells are multinucleate
Striated – have visible banding
Voluntary – subject to conscious control
Cells are surrounded and bundled by connective tissue
Slide 6.3
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

5. Connective Tissue Wrappings of Skeletal Muscle
Endomysium – around single muscle fiber
Perimysium – around a fascicle (bundle) of fibers
Figure 6.1
Slide 6.4a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

6. Connective Tissue Wrappings of Skeletal Muscle
Epimysium – covers the entire skeletal muscle
Fascia – on the outside of the epimysium
Figure 6.1
Slide 6.4b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

7. Skeletal Muscle Attachments
Epimysium blends into a connective tissue attachment
Tendon – cord-like structure
Mostly collagen fibers
Often cross a joint due to toughness and small size
Aponeuroses – sheet-like structure
Attach muscles indirectly to bones, cartilage or connective tissue covering
Slide 6.5
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

8. Skeletal Muscle Attachments
Sites of muscle attachment
Bones
Cartilages
Connective tissue coverings
Slide 6.5
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

9. Smooth Muscle Characteristics
Has no striations
Spindle-shaped cells
Single nucleus
Involuntary – no conscious control
Found mainly in the walls of hollow organs
Figure 6.2a
Slide 6.6
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

10. Cardiac Muscle Characteristics
Has striations
Usually has a single nucleus
Joined to another muscle cell at an intercalated disc
Involuntary
Found only in the heart
Figure 6.2b
Slide 6.7
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

11. Function of Muscles Produce movement Maintain posture Stabilize joints
Generate heat
Slide 6.8
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

12. Microscopic Anatomy of Skeletal Muscle
Cells are multinucleate
Nuclei are just beneath the sarcolemma
Figure 6.3a
Slide 6.9a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

13. Microscopic Anatomy of Skeletal Muscle
Sarcolemma – specialized plasma membrane
Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum
Figure 6.3a
Slide 6.9b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

14. Microscopic Anatomy of Skeletal Muscle
Myofibril – long organelles inside muscle cells
Bundles of myofilaments
Myofibrils are aligned to give distrinct bands
I band = light band
Thin filaments
A band = dark band
Thick filaments
Slide 6.10a

15. Microscopic Anatomy of Skeletal Muscle
Sarcomere
Contractile unit of a muscle fiber
Figure 6.3b
Slide 6.10b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

16. Microscopic Anatomy of Skeletal Muscle
Organization of the sarcomere
Thick filaments = myosin filaments
Composed of the protein myosin
Has ATPase enzymes
Figure 6.3c
Slide 6.11a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

17. Microscopic Anatomy of Skeletal Muscle
Organization of the sarcomere
Thin filaments = actin filaments
Composed of the protein actin
Figure 6.3c
Slide 6.11b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

18. Microscopic Anatomy of Skeletal Muscle
Myosin filaments have heads (extensions, or cross bridges)
Myosin and actin overlap somewhat
Anchored to the
Z disc
Figure 6.3d
Slide 6.12a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

19. Microscopic Anatomy of Skeletal Muscle
At rest, there is a bare zone that lacks actin filaments called the H zone
Sarcoplasmic reticulum (SR) – for storage of calcium
Figure 6.3d
Slide 6.12b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

20. Properties of Skeletal Muscle Activity
Irritability – ability to receive and respond to a stimulus
Contractility – ability to shorten when an adequate stimulus is received
Slide 6.13
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

21. Properties of Skeletal Muscle Activity
Extensibility – ability of muscle cells to stretched
Elasticity – ability to recoil and resume resting length after stretching
Slide 6.13
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

22. Nerve Stimulus to Muscles
Skeletal muscles must be stimulated by a motor neuron (nerve cell) to contract
Motor unit
One motor neuron
Skeletal muscle cells stimulated by that neuron
Figure 6.4a
Slide 6.14

23. Nerve Stimulus to Muscles
Neuromuscular junctions – association site of axon terminal of the motor neuron and muscle
Figure 6.5b
Slide 6.15a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

24. Nerve Stimulus to Muscles
Synaptic cleft – gap between nerve and muscle
Nerve and muscle do not make contact
Area between nerve and muscle is filled with interstitial fluid
Figure 6.5b
Slide 6.15b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

25. Transmission of Nerve Impulse to Muscle
Neurotransmitter – chemical released by nerve upon arrival of nerve impulse
The neurotransmitter for skeletal muscle is acetylcholine (ACh)
Neurotransmitter (Acetylcholine) attaches to receptors on the sarcolemma
Sarcolemma becomes permeable to sodium (Na+)
Slide 6.16a

26. Transmission of Nerve Impulse to Muscle
Sodium rushing into the cell generates an action potential
Once started, muscle contraction cannot be stopped
Slide 6.16b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

27. The Sliding Filament Theory of Muscle Contraction
Activation by nerve causes myosin heads (cross bridges) to attach to binding sites on the thin filament
Myosin heads then bind to the next site of the thin filament pulls them towards the center of the sarcomere
Figure 6.7
Slide 6.17a

28. The Sliding Filament Theory of Muscle Contraction
This continued action causes a sliding of the myosin along the actin
The result is that the muscle is shortened (contracted)
Figure 6.7
Slide 6.17b

29. The Sliding Filament Theory of Muscle Contraction
This continued action causes a sliding of the myosin along the actin
The result is that the muscle is shortened (contracted)
Figure 6.7
Slide 6.17b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

30. The Sliding Filament Theory
Figure 6.8
Slide 6.18
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

31. Contraction of a Skeletal Muscle
Muscle fiber contraction is “all or none”
Within a skeletal muscle, not all fibers may be stimulated during the same interval
Different combinations of muscle fiber contractions may give differing responses
Slide 6.19
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

32. Contraction of a Skeletal Muscle
Graded responses – different degrees of skeletal muscle shortening
Graded responses can be produced by changing:
The frequency of muscle stimulation
The number of muscle cells being stimulated at one time
Slide 6.19
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

33. Types of Graded Responses
Twitch
Single, brief contraction
Not a normal muscle function
Figure 6.9a, b
Slide 6.20a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

34. Types of Graded Responses
Tetanus (summing of contractions)
One contraction is immediately followed by another
The muscle does not completely return to a resting state
The effects are added
Figure 6.9a, b
Slide 6.20b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

35. Types of Graded Responses
Unfused (incomplete) tetanus
Some relaxation occurs between contractions
The results are summed
Figure 6.9a, b
Figure 6.9c,d
Slide 6.21a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

36. Types of Graded Responses
Fused (complete) tetanus
No evidence of relaxation before the following contractions
The result is a sustained muscle contraction
Figure 6.9a, b
Figure 6.9c,d
Slide 6.21b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

37. Muscle Response to Strong Stimuli
Muscle force depends upon the number of fibers stimulated
More fibers contracting results in greater muscle tension
Muscles can continue to contract unless they run out of energy
Slide 6.22
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

38. Energy for Muscle Contraction
Initially, muscles used stored ATP for energy
Bonds of ATP are broken to release energy
Only 4-6 seconds worth of ATP is stored by muscles
After this initial time, other pathways must be utilized to produce ATP
Slide 6.23
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

39. Energy for Muscle Contraction
Direct phosphorylation
Muscle cells contain creatine phosphate (CP)
CP is a high-energy molecule
After ATP is depleted, ADP is left
CP transfers energy to ADP, to regenerate ATP
CP supplies are exhausted in about 20 seconds
Slide 6.24
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 6.10a

40. Energy for Muscle Contraction
Aerobic Respiration
Series of metabolic pathways that occur in the mitochondria
Glucose is broken down to carbon dioxide and water, releasing energy
This is a slower reaction that requires continuous oxygen
Figure 6.10c
Slide 6.25
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

41. Energy for Muscle Contraction
Anaerobic glycolysis
Reaction that breaks down glucose without oxygen
Glucose is broken down to pyruvic acid to produce some ATP
Pyruvic acid is converted to lactic acid
Slide 6.26a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 6.10b

42. Energy for Muscle Contraction
Anaerobic glycolysis (continued)
This reaction is not as efficient, but is fast
Huge amounts of glucose are needed
Lactic acid produces muscle fatigue
Slide 6.26b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 6.10b

43. Muscle Fatigue and Oxygen Debt
When a muscle is fatigued, it is unable to contract even with a stimulus
The common reason for muscle fatigue is oxygen debt
Oxygen must be “repaid” to tissue to remove oxygen debt
Oxygen is required to get rid of accumulated lactic acid
Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less
Slide 6.27
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

44. Types of Muscle Contractions
Isotonic contractions
Myofilaments are able to slide past each other during contractions
The muscle shortens
Isometric contractions
Tension in the muscles increases
The muscle is unable to shorten
Slide 6.28
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

45. Muscle Tone Some fibers are contracted even in a relaxed muscle
Different fibers contract at different times to provide muscle tone
The process of stimulating various fibers is under involuntary control
Slide 6.29
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

46. Effect of Exercise on Muscles
Exercise increases muscle size, strength, and endurance
Aerobic (endurance), exercise (biking, jogging) results in stronger, more flexible muscles with greater resistance to fatigue
Makes body metabolism more efficient
Improves digestion, coordination
Resistance (isometric), exercise muscle size and strength
Slide 6.29

47. Effects of Exercise on Muscle
Results of increased muscle use
Increase in muscle size
Increase in muscle strength
Increase in muscle efficiency
Muscle becomes more fatigue resistant
Slide 6.31
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

48. Muscles and Body Movements
Movement is attained due to a muscle moving an attached bone
Figure 6.12
Slide 6.30a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

49. Muscles and Body Movements
Muscles are attached to at least two points
Origin – attachment to a immoveable bone
Insertion – attachment to an movable bone
Figure 6.12
Slide 6.30b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

50. Types of Ordinary Body Movements
Flexion
Decreased the angle of the joint
Brings two bones closer together
Typical hinge joints like knee and elbow
Slide 6.32
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

51. Types of Ordinary Body Movements
Extension
Opposite of flexion
Increases angle between two bones
Rotation
Movement of a bone around its longitudinal axis
Common example of ball-and-socket
Slide 6.32

52. Types of Ordinary Body Movements
Abduction
Movement of a limb away from the midline
Adduction
Movement of a limb towards the midline
Slide 6.32
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

53. Types of Ordinary Body Movements
Circumduction
Common in ball-and socket joints
Slide 6.32
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

54. Body Movements Figure 6.13 Slide 6.33
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

55. Special Movements Dorsifelxion Plantar flexion Inversion Eversion
Supination
Pronation
Opposition
Slide 6.34
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

56. Types of Muscles
Prime mover – muscle with the major responsibility for a certain movement
Antagonist – muscle that opposes or reverses a prime mover
Synergist – muscle that aids a prime mover in a movement and helps prevent rotation
Fixator – stabilizes the origin of a prime mover
Slide 6.35
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

57. Naming of Skeletal Muscles
Direction of muscle fibers
Example: rectus (straight)
Relative size of the muscle
Example: maximus (largest)
Slide 6.36a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

58. Naming of Skeletal Muscles
Location of the muscle
Example: many muscles are named for bones (e.g., temporalis)
Number of origins
Example: triceps (three heads)
Slide 6.36b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

59. Naming of Skeletal Muscles
Location of the muscles origin and insertion
Example: sterno (on the sternum)
Shape of the muscle
Example: deltoid (triangular)
Action of the muscle
Example: flexor and extensor (flexes or extends a bone)
Slide 6.37
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

60. Head and Neck Muscles Figure 6.14 Slide 6.38
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

61. Trunk Muscles Figure 6.15 Slide 6.39
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

62. Deep Trunk and Arm Muscles
Figure 6.16
Slide 6.40
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

63. Muscles of the Pelvis, Hip, and Thigh
Figure 6.18c
Slide 6.41
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

64. Muscles of the Lower Leg
Figure 6.19
Slide 6.42
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

65. Superficial Muscles: Anterior
Figure 6.20
Slide 6.43
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

66. Superficial Muscles: Posterior
Figure 6.21
Slide 6.44
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings