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Hole’s HumanAnatomy and Physiology

Eleventh Edition

Mrs. Hummer

Chapter

9

Muscular System

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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

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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

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Connective Tissue Coverings

• muscle• fascicles-bundles ofskeletal muscle fibers• muscle fibers• myofibrils-contractilefibers• thick and thinfilaments

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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

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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

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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

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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

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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)

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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)

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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

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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

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Heat Production Length-Tension Relationship

• by-product of cellular respiration

• muscle cells are major source of body heat

• blood transports heat throughout body

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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

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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

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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

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Characteristics of Muscle Tissue

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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

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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

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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

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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

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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

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Major Skeletal Muscles

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Muscles of Facial Expression

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Muscles of Mastication

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Muscles of Facial Expressionand Mastication

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Muscles That Move the Headand Vertebral Column

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Muscles That Move the Headand Vertebral Column

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Muscles That Move thePectoral Girdle

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Muscles That Move thePectoral Girdle

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Muscles That Move the Arm

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Muscles That Move the Arm

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Muscles That Move the Arm

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Muscles That Move theForearm

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Muscles That Move theForearm

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Muscles That Move theForearm

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Cross Section of the Forearm

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Muscles That Move the Hand

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Muscles That Move the Hand

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Muscles of the Abdominal Wall

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Muscles of the Abdominal Wall

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Muscles of the Pelvic Outlet

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Muscles of Pelvic Outlet

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Muscles That Move the Thigh

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Muscles That Move the Thigh

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Muscles That Move the Thigh

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Muscles That Move the Leg

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Muscles That Move the Leg

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Muscles That Move the Leg

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Muscles That Move the Leg

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Muscles That Move the Foot

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Muscles That Move the Foot

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Muscles That Move the Foot