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

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

3. Cardiac Muscle Characteristics Slide 6.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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

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

5. Skeletal Muscle Characteristics: Slide 6.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 1.Most are attached by tendons to bones 2.Cells are multinucleate 3.Striated – have visible banding 4.Voluntary control 5.Cells are surrounded and bundled by connective tissue wrappings

6. Characteristics of Muscles Slide 6.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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

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

8. Connective Tissue Wrappings of Skeletal Muscle Slide 6.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 1.Endomysium – around single muscle fiber 2.Perimysium – around a fascicle (bundle) of fibers Figure 6.1

9. Connective Tissue Wrappings of Skeletal Muscle Slide 6.4b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 3.Epimysium – covers the entire skeletal muscle 4.Fascia – on the outside of the epimysium Figure 6.1

10. Skeletal Muscle Attachments Slide 6.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Epimysium blends into a connective tissue attachment  Tendon – cord-like structure  Aponeuroses – sheet-like structure  Sites of muscle attachment  Bones  Cartilages  Connective tissue coverings

11. Microscopic Anatomy of Skeletal Muscle Slide 6.9a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Cells are multinucleate  Nuclei are just beneath the sarcolemma ( specialized plasma membrane of muscle cells) Figure 6.3a

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

13. Microscopic Anatomy of Skeletal Muscle Slide 6.10a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Myofibril - bu ndles of myofilaments  aligned to give distrinct bands  I band = light band  A band = dark band Figure 6.3b

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

15. Microscopic Anatomy of Skeletal Muscle Slide 6.11a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Organization of the sarcomere:  Thick filaments = myosin filaments; has ATPase enzymes  Thin filaments = actin filaments Figure 6.3c

16. Microscopic Anatomy of Skeletal Muscle Slide 6.12a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Myosin filaments have heads (extensions, or cross bridges)  Myosin and actin overlap somewhat

17. Microscopic Anatomy of Skeletal Muscle Slide 6.12b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  At rest, there is a bare zone that lacks actin filaments (H-zone)  Sarcoplasmic reticulum (SR/SER) – for storage of calcium

18. Mechanism of Muscle Contraction: The Sliding filament Theory Requirements: Nerve impulse, action potential, and Ca ++ ions (stored in SER) 1. Nerve impulse reaches axon terminal at neuromuscular junction, and releases the neurotransmiter, acetylcholine (Ach). 2. Ach produces an action potential along the sarcolemma that releases Ca++ from storage – SER 3. An increase flow of Ca++ allows for myosin crossbridges to attach to binding sites on actin filaments to slide and the muscle cell shortens. 4. When the action potential ends, Ca++ are immediately reabsorbed into storage areas, the muscle relaxes, and returns to its original length.

19. Note: As the action potential is occurring Ach is breaking down to prevent continued contraction of the muscle cell in the absence of additional nerve impulses. (All or none principle) Time: whole series takes a few thousandth's of a second. Mechanism of Muscle Contraction: The Sliding filament Theory (cont.d)

20. The Sliding Filament Theory of Muscle Contraction Slide 6.17a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Activation by nerve causes myosin heads (crossbridges) to attach to binding sites on the thin filament  Myosin heads then bind to the next site of the thin filament Figure 6.7

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

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

23. Nerve Stimulus to Muscles Slide 6.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Skeletal muscles must be stimulated by a nerve to contract  Motor unit  One neuron  Muscle cells stimulated by that neuron Figure 6.4a

24. Nerve Stimulus to Muscles Slide 6.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neuromuscular junctions – association site of nerve and muscle Figure 6.5b

25. Nerve Stimulus to Muscles Slide 6.15b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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

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

27. Transmission of Nerve Impulse to Muscle Slide 6.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neurotransmitter – chemical released by nerve upon arrival of nerve impulse  The neurotransmitter for skeletal muscle is acetylcholine  Neurotransmitter attaches to receptors on the sarcolemma  Sarcolemma becomes permeable to sodium (Na + )

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

29. Contraction of a Skeletal Muscle Slide 6.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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  Graded responses – different degrees of skeletal muscle shortening

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

31. Types of Graded Responses Slide 6.20b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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

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

33. Types of Graded Responses Slide 6.21b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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

34. Muscle Response to Strong Stimuli Slide 6.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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

35. Energy for Muscle Contraction Slide 6.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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

36. Energy for Muscle Contraction Slide 6.24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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 Figure 6.10a

37. Energy for Muscle Contraction Slide 6.25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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

38. Energy for Muscle Contraction Slide 6.26a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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 Figure 6.10b

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

40. Muscle Fatigue and Oxygen Debt Slide 6.27 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  When a muscle is fatigued, it is unable to contract  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

41. Types of Muscle Contractions Slide 6.28 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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

42. Muscle Tone Slide 6.29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  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

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

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

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