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1
Hole’s HumanAnatomy and Physiology
Eleventh Edition
Mrs. Hummer
Chapter
9
Muscular System
2
Chapter 9Muscular System
Three Types of Muscle Tissues
Skeletal Muscle• usually attachedto bones• under consciouscontrol• striated
Smooth Muscle• walls of most viscera,blood vessels, skin• not under consciouscontrol• not striated
Cardiac Muscle• wall of heart• not underconscious control• striated
3
Structure of a Skeletal Muscle
Skeletal Muscle• organ of the muscularsystem - skeletal muscle tissue - nervous tissue - blood - connective tissues• fascia• tendons• aponeuroses- sheet ofconnective tissue ofwhich certain musclesare attached to bone andfacia
4
Connective Tissue Coverings
• muscle• fascicles-bundles ofskeletal muscle fibers• muscle fibers• myofibrils-contractilefibers• thick and thinfilaments
5
Skeletal Muscle Fibers• sarcolemma-cell membrane• sarcoplasm- cytoplasm• sarcoplasmic reticulum- likeE.R• transverse tubule-channelthat extends inward• triad
• cisternae of sarcoplasmicreticulum• transverse tubule
• myofibril- contractile fiberin muscle cells• actin filaments (thin)• myosin filaments (thick)• sarcomere-unit of amyofibril
6
Myofilaments
Thick Filaments • composed of myosin• cross-bridges
Thin Filaments• composed of actin• associated with troponinand tropomyosin (proteins)
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Neuromuscular Junction• also known asmyoneural junction
• site where an axon andmuscle fiber meet
• motor neuron
8
Stimulus for Contraction
• acetylcholine (ACh)(neurotransmitter)• nerve impulse causes releaseof ACh from synaptic vesicles• ACh binds to ACh receptorson motor end plate• generates a muscle impulse• muscle impulse eventuallyreaches sarcoplasmicreticulumand the cisternae
9
Excitation ContractionCoupling
• muscle impulses causesarcoplasmic reticulum torelease calcium ions intocytosol• calcium binds to troponin tochange its shape• position of tropomyosin isaltered• binding sites on actin areexposed• actin and myosin moleculesbind
10
Relaxation
• acetylcholinesterase – rapidly decomposes Ach remaining in the synapse
• muscle impulse stops
• stimulus to sarcolemma and muscle fiber membrane ceases
• calcium moves back into sarcoplasmic reticulum
• myosin and actin binding prevented
• muscle fiber relaxes
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Major Events of MuscleContraction and Relaxation
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Energy Sources forContraction
• creatine phosphate– stores energy thatquickly converts ADPto ATP
1) Creatine phosphate; 4-6 times more abundant in muscle cells than ATP2) Cellular respiration (ATP)
13
Oxygen Supply andCellular Respiration
• Anaerobic Phase• glycolysis• occurs in cytoplasm• produces little ATP
• Aerobic Phase• citric acid cycle• electron transport chain• occurs in the mitochondria• produces most ATP• myoglobin stores extraoxygen (pigment that givesmuscle the reddish-browncolor)
14
Oxygen Debt
• oxygen not available• glycolysis continues• pyruvic acidconverted to lactic acid• liver converts lacticacid to glucose
Oxygen debt – amount of oxygen needed by liver cells touse the accumulated lactic acid to produce glucose
15
Muscle Fatigue
• inability to contract
• commonly caused from • decreased blood flow• ion imbalances across the sarcolemma• accumulation of lactic acid
• cramp – sustained, involuntary muscle contraction
16
Heat Production Length-Tension Relationship
• by-product of cellular respiration
• muscle cells are major source of body heat
• blood transports heat throughout body
17
Types of Contractions
• isotonic – muscle contracts andchanges length
• concentric – shortening contraction
• eccentric – lengtheningcontraction
• isometric – muscle contracts butdoes not change length
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Smooth Muscle Fibers
Compared to skeletal muscle fibers• shorter• single, centrally located nucleus• elongated with tapering ends• myofilaments randomly organized• lack striations• lack transverse tubules• sarcoplasmic reticula not welldeveloped
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Types of Smooth Muscle
Visceral Smooth Muscle• single-unit smooth muscle• sheets of muscle fibers• fibers held together by gapjunctions• exhibit rhythmicity• exhibit peristalsis• walls of most hollow organs
Multiunit Smooth Muscle• less organized• function as separate units • fibers function separately• irises of eye• walls of blood vessels
20
Smooth Muscle Contraction
• Resembles skeletal muscle contraction• interaction between actin and myosin• both use calcium and ATP• both are triggered by membrane impulses
• Different from skeletal muscle contraction• smooth muscle lacks troponin• smooth muscle uses calmodulin (protein) • two neurotransmitters affect smooth muscle
• acetlycholine and norepinephrine• hormones affect smooth muscle• stretching can trigger smooth muscle contraction• smooth muscle slower to contract and relax• smooth muscle more resistant to fatigue• smooth muscle can change length without changing
tautness
21
Cardiac Muscle
• located only in the heart
• muscle fibers joined together by intercalated discs
• fibers branch
• network of fibers contracts as a unit
• self-exciting and rhythmic
22
Characteristics of Muscle Tissue
23
Skeletal Muscle Actions
• origin – immovable end• insertion – movable end
• prime mover (agonist) –primarily responsible formovement• synergists – assist prime mover• antagonist – resist primemover’s action and causemovement in the oppositedirection
24
Body Movement
Four Basic Components of Lever1. rigid bar – bones2. fulcrum – point on which bar moves; joint3. object - moved against resistance; weight4. force – supplies energy for movement; muscles
25
Clinical Application
Myasthenia Gravis
• autoimmune disorder• receptors for ACh on muscle cells are attacked• weak and easily fatigued muscles result• difficulty swallowing and chewing• ventilator needed if respiratory muscles are affected• treatments include
• drugs that boost ACh• removing thymus gland• immunosuppressant drugs• antibodies
26
Life-Span Changes
• myoglobin, ATP, and creatine phosphatedecline
• by age 80, half of muscle mass hasatrophied
• adipose cells and connective tissues replacemuscle tissue
• exercise helps to maintain muscle mass andfunction
27
Notebook
Understanding Words
Pg. 341
Critical Thinking:
#1, 2, 3
Review Questions:
#1, 8, 10, 11, 12, 13, 14, 23, 25, 29
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Major Skeletal Muscles
29
Major Skeletal Muscles
30
Muscles of Facial Expression
31
Muscles of Mastication
32
Muscles of Facial Expressionand Mastication
33
Muscles That Move the Headand Vertebral Column
34
Muscles That Move the Headand Vertebral Column
35
Muscles That Move thePectoral Girdle
36
Muscles That Move thePectoral Girdle
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Muscles That Move the Arm
38
Muscles That Move the Arm
39
Muscles That Move the Arm
40
Muscles That Move theForearm
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Muscles That Move theForearm
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Muscles That Move theForearm
43
Cross Section of the Forearm
44
Muscles That Move the Hand
45
Muscles That Move the Hand
46
Muscles of the Abdominal Wall
47
Muscles of the Abdominal Wall
48
Muscles of the Pelvic Outlet
49
Muscles of Pelvic Outlet
50
Muscles That Move the Thigh
51
Muscles That Move the Thigh
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Muscles That Move the Thigh
53
Muscles That Move the Leg
54
Muscles That Move the Leg
55
Muscles That Move the Leg
56
Muscles That Move the Leg
57
Muscles That Move the Foot
58
Muscles That Move the Foot
59
Muscles That Move the Foot