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The Muscular System 1. Muscles are responsible for all types of body movement Three basic muscle types are found in the body –Skeletal muscle –Cardiac.

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Presentation on theme: "The Muscular System 1. Muscles are responsible for all types of body movement Three basic muscle types are found in the body –Skeletal muscle –Cardiac."— Presentation transcript:

1 The Muscular System 1

2 Muscles are responsible for all types of body movement Three basic muscle types are found in the body –Skeletal muscle –Cardiac muscle –Smooth muscle 2

3 Characteristics of Muscles 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 3

4 Smooth Muscle Characteristics Has no striations Spindle-shaped cells Single nucleus Involuntary – no conscious control Found mainly in the walls of hollow organs 4

5 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 5

6 Classification of muscle Voluntary Involuntary Limbs Heart Viscera Striated Non-striated SkeletalCardiac Smooth Note: Control, Location and Structure 6

7 Muscle Control Type of muscle Nervous control Type of control Example Skeletal Controlled by CNS Voluntary Lifting a glass Cardiac Regulated by ANS Involuntary Heart beating Smooth Controlled by ANS Involuntary Peristalsis 7

8 There are about 650 muscles in the human body. They enable us to move, maintain posture and generate heat. In this section we will only study a sample of the major muscles. Skeletal Muscle 8

9 Function of Skeletal Muscles Produce movement Maintain posture Stabilize joints Generate heat 9

10 Skeletal Muscle Characteristics Most are attached by tendons to bones 10

11 Skeletal Muscle Characteristics Cells are multinucleate Striated – have visible banding Voluntary – subject to conscious control Cells are surrounded and bundled by connective tissue 11

12 Connective Tissue Wrappings of Skeletal Muscle Endomysium – around single muscle fiber Perimysium – around a fascicle (bundle) of fibers 12

13 Connective Tissue Wrappings of Skeletal Muscle Epimysium – covers the entire skeletal muscle Fascia – on the outside of the epimysium 13

14 Skeletal Muscle Attachments Epimysium blends into a connective tissue attachment –Tendon – cord-like structure –Aponeuroses – sheet-like structure Sites of muscle attachment –Bones –Cartilages –Connective tissue coverings 14

15 Microscopic Anatomy of Skeletal Muscle Cells are multinucleate Nuclei are just beneath the sarcolemma 15

16 Microscopic Anatomy of Skeletal Muscle Sarcolemma – specialized plasma membrane Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum 16

17 Microscopic Anatomy of Skeletal Muscle Myofibril –Bundles of myofilaments –Myofibrils are aligned to give distinct bands I band = light band A band = dark band 17

18 Microscopic Anatomy of Skeletal Muscle Sarcomere –Contractile unit of a muscle fiber 18

19 Microscopic Anatomy of Skeletal Muscle Organization of the sarcomere –Thick filaments = myosin filaments Composed of the protein myosin Has ATPase enzymes 19

20 Microscopic Anatomy of Skeletal Muscle Organization of the sarcomere –Thin filaments = actin filaments Composed of the protein actin 20

21 Microscopic Anatomy of Skeletal Muscle Myosin filaments have heads (extensions, or cross bridges) Myosin and actin overlap somewhat 21

22 Microscopic Anatomy of Skeletal Muscle At rest, there is a bare zone that lacks actin filaments Sarcoplasmic reticulum (SR) – for storage of calcium 22

23 To Summarize... Skeletal muscle tissue is made of cells called muscle fibers. Muscle fibers contain small cylinders called myofibrils. Myofibrils are made of sarcomeres linked end-to-end. 23

24 Muscle Contraction 24

25 Properties of Skeletal Muscle Activity Irritability – ability to receive and respond to a stimulus Contractility – ability to shorten when an adequate stimulus is received 25

26 Nerve Stimulus to Muscles Skeletal muscles must be stimulated by a nerve to contract Motor unit –One neuron –Muscle cells stimulated by that neuron 26

27 Nerve Stimulus to Muscles Neuromuscular junctions – association site of nerve and muscle 27

28 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 28

29 Transmission of Nerve Impulse to Muscle 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 + ) 29

30 Transmission of Nerve Impulse to Muscle Sodium rushing into the cell generates an action potential Once started, muscle contraction cannot be stopped 30

31 When a muscle is relaxed, myosin and actin filaments are not attached. The Steps in Muscle Contraction 31

32 1.Myosin attaches to a binding site on an actin filament. Calcium is required to make a binding site available for myosin. The Steps in Muscle Contraction 32

33 The Sliding Filament Theory 33

34 2.The myosin head rotates and causes the actin filament to slide along the myosin filament. The sliding causes the filaments to overlap more, and the sarcomere becomes shorter. The Steps in Muscle Contraction 34

35 During contraction, myosin attaches to binding sites on actin, forming cross-bridges. Using ATP, the cross- bridges pull the actin toward the center of the sarcomere. The Steps in Muscle Contraction 35

36 3.After the myosin head has rotated as far as it can, it must let go of the actin fiber. ATP is required for myosin to detach from actin. The myosin head snaps back into its original position, using the energy in the ATP. The ATP becomes ADP and releases a phosphate ion. The Steps in Muscle Contraction 36

37 The Steps in Muscle Contraction 4.Calcium exposes a new actin binding site and myosin reattaches to actin. Steps 1 through 3 happen again. 37

38 The cross-bridges break, myosin binds to another site, and the cycle begins again until the muscle fiber is contracted. The Steps in Muscle Contraction 38

39 To summarize... Myosin filaments bind to actin filaments, actin filaments move inward, and sarcomeres shorten to cause muscle contraction. 39

40 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 Graded responses – different degrees of skeletal muscle shortening 40

41 Types of Graded Responses Twitch –Single, brief contraction –Not a normal muscle function 41

42 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 42

43 Types of Graded Responses Unfused (incomplete) tetanus –Some relaxation occurs between contractions –The results are summed 43

44 Types of Graded Responses Fused (complete) tetanus –No evidence of relaxation before the following contractions –The result is a sustained muscle contraction 44

45 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 45

46 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 46

47 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 47

48 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 48

49 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 49

50 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 50

51 Begin October 18,

52 The Muscular System 52

53 Five Golden Rules of Gross Muscle Activity 1.all muscles cross at least one joint 2.bulk of muscles lies proximal to the joint crossed 3.all muscles have at least 2 attachments: origin & insertion 4.muscles only pull/never push 5.during contraction the muscle insertion moves toward the origin 53

54 Muscles and Body Movements Movement is attained due to a muscle moving an attached bone 54

55 Muscles and Body Movements Muscles are attached to at least two points –Origin – attachment to an immoveable bone –Insertion – attachment to a movable bone 55

56 The Muscular System 56

57 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 Myofilaments “skidding their wheels” 57

58 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 stimulating various fibers is under fibers is under involuntary control involuntary control 58

59 Muscle Tone When muscles are not worked they atrophy (waste away) and become flaccid. 59

60 Effects of Exercise on Muscle Aerobics result in stronger muscles due to increase blood supply Muscle fibers increase mitochondria and oxygen storage Muscle becomes more fatigue resistant Heart enlarges to pump more blood to body more blood to body Does not increase skeletal muscle size 60

61 Results of increased muscle use from resistance training Individual muscle cells make more contractile filaments & connective tissue increases –Increase in muscle size –Increase in muscle strength Effects of Exercise on Muscle 61

62 Begin October 19,

63 Muscle Fatigue and Oxygen Debt 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 63

64 The Muscular System 64

65 Types of Ordinary Body Movements FlexionExtensionRotationAbductionCircumduction 65

66 Flexion & Extension 66

67 Flexion & Extension 67

68 Rotation 68

69 Abduction & Adduction 69

70 Special Movements Dorsiflexion Plantar flexion InversionEversionSupinationPronationOpposition 70

71 Dorsiflexion & Plantar Flexion 71

72 Inversion & Eversion 72

73 Pronation & Supination 73

74 Opposition 74

75 75

76 76

77 77

78 Diseases and Disorders of the Muscular System Myalgia: Muscle pain due to strain, tearing of muscle fibers. It also is a symptom of an immune response along with a fever. Myositis: Inflammation of muscle tissue due to injury or disease. Charley Horse (fibromyositis): Inflammation of muscle tissue and the tendons associated with that muscle due to injury (tear or severe bruising- contusion) Cramps: Painful, involuntary muscle spasms 78

79 Cerebral Palsy This disorder is characterized by paralysis and or weakened muscles due to loss of muscle tone. It can be caused due to lack of oxygen to the region of the motor region of the cerebrum of the brain which controls conscious control of muscles. This is often attributed to complication during birth. 79

80 Poliomyelitis Poliomyelitis: Polio is due to a viral infection which affects the motor neurons that control skeletal muscles. It often leads to paralysis and can result in death by paralysis of the diaphragm. Due to vaccine developed by Jonas Salk, the virus has been virtually eliminated in the US. However, it still poses a threat in developing countries. 80

81 Muscular Dystrophy Congenital muscle-destroying disease affect specific muscle groups Muscle fibers degenerate & atrophy due to an absence of dystrophin, a protein that helps keep muscle cells intact Duchenne’s M.D. Most common & serious— –Mostly in males (diagnosed between2-6 yrs) –Survival is rare beyond early 30’s –X-linked recessive 81

82 Myasthenia gravis Rare adult disease caused by antibodies to acetylcholine receptors at the neuromuscular junction which prevents the muscle contraction from occurring Drooping upper eyelids, difficulty swallowing & talking, muscle weakness & fatigue Death occurs when respiratory muscles cease to function 82

83 Aging Connective Tissue increases Amount of Muscle tissue decreases Muscles become stringier(sinewy) Body weight declines due to loss of muscle mass By age 80, muscle strength usually decrease by 50% without weight training exercises 83

84 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 84

85 Naming of Skeletal Muscles Direction of muscle fibers –Example: rectus (straight) Relative size of the muscle –Example: maximus (largest) 85

86 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) 86

87 Naming of Skeletal Muscles Location of the muscle’s 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) 87

88 Head and Neck Muscles 88

89 Trunk Muscles 89

90 Deep Trunk and Arm Muscles 90

91 Muscles of the Pelvis, Hip, and Thigh 91

92 Muscles of the Lower Leg 92

93 Superficial Muscles: Anterior 93

94 Superficial Muscles: Posterior 94


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