Chapter 9 Muscular System

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chapter 9Lecture

PowerPoint

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2401Anatomy and Physiology I

Chapter 9

Susan Gossett

[email protected]

Department of Biology

Paris Junior College

mailto:[email protected]

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Hole’s Human Anatomyand Physiology

Twelfth Edition

Shier Butler Lewis

Chapter 9

Muscular System


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9.1: Introduction

Three (3) Types of Muscle Tissues

• Skeletal Muscle• Usually attached to bones• Voluntary• Somatic• Striated

• Smooth Muscle• Walls of most viscera, blood vessels and skin• Involuntary• Autonomic• Not striated

• Cardiac Muscle• Wall of heart• Involuntary• Autonomic• Striated

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9.2: Structure of Skeletal Muscle

• Skeletal Muscle• Organ of the muscular system

• Skeletal muscle tissue• Nervous tissue• Blood• Connective tissues

• Fascia• Tendons• Aponeuroses


Aponeuroses

Skeletal muscles

Tendons

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Connective Tissue Coverings

• Muscle coverings:• Epimysium• Perimysium• Endomysium

Bone

Muscle

EpimysiumPerimysium

Endomysium

Fascicle

Fascicles

Muscle fibers (cells)

Myofibrils

Thick and thin filaments

Blood vessel

Muscle fiber

Myofibril

Sarcolemma

Nucleus Filaments

Tendon

Fascia(covering muscle)

Axon of motorneuron

Sarcoplasmicreticulum


• Muscle organ• Fascicles• Muscle cells or fibers• Myofibrils• Thick and thin myofilaments

• Actin and myosin proteins• Titin is an elastic myofilament

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Skeletal Muscle Fibers

• Sarcolemma• Sarcoplasm• Sarcoplasmic reticulum (SR)• Transverse (‘T’) tubule• Triad

• Cisternae of SR• T tubule

• Myofibril• Actin myofilaments• Myosin myofilaments• Sarcomere


Nucleus

Mitochondria

SarcolemmaSarcoplasm

Nucleus

Myofibrils


Openings intotransverse tubules

Thick and thinfilaments

Cisternae ofsarcoplasmic reticulum

Transverse tubuleTriad

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9.3: Skeletal Muscle Contraction

• Movement within the myofilaments• I band (thin)• A band (thick and thin)• H zone (thick)• Z line (or disc)• M line


Myofibril

Sarcomere

(a)

Skeletal muscle fiber

Z lineH zone M line

I band I band

(b)

Z line


Thick (myosin)filaments

Thin (actin)filaments

A bandA band

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Myofilaments

• Thick myofilaments • Composed of myosin protein• Form the cross-bridges

• Thin myofilaments• Composed of actin protein• Associated with troponin and tropomyosin proteins


Cross-bridges

Actin molecule

Thin filament

Myosinmolecule

Thickfilament

Troponin Tropomyosin

Neuromuscular Junction• Also known as NMJ or myoneural junction

• Site where an axon and muscle fiber meet

• Parts• Motor neuron

• Motor end plate• Synapse

• Synaptic cleft

• Synaptic vesicles

• Neurotransmitters


Axon branches

Mitochondria

Acetylcholine

(a)

Synapticvesicles

Synapticcleft

Foldedsarcolemma

Motorend plate

Myofibril ofmuscle fiber

Muscle fibernucleus

Motorneuron axon

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Motor Unit

• Single motor neuron• All muscle fibers controlled by motor neuron• As few as four fibers• As many as 1000’s of muscle fibers


Motor neuronof motor unit 2

Motor neuronof motor unit 1

Skeletal musclefibers

Branches ofmotor neuronaxon

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Stimulus for Contraction

• Acetylcholine (ACh)• Nerve impulse causes release of ACh from synaptic vesicles• ACh binds to ACh receptors on motor end plate• Generates a muscle impulse• Muscle impulse eventually reaches the SR and the cisternae


Axon branches

Mitochondria

Acetylcholine

(a)

Synapticvesicles

Synapticcleft

Foldedsarcolemma

Motorend plate

Myofibril ofmuscle fiber

Muscle fibernucleus

Motorneuron axon

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9.1 Clinical Application

Myasthenia Gravis

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Excitation-Contraction Coupling

• Muscle impulses cause SR to release calcium ions into cytosol• Calcium binds to troponin to change its shape• The position of tropomyosin is altered• Binding sites on actin are now exposed• Actin and myosin molecules bind via myosin cross-bridges


Actin monomers

Release of Ca+2 from sarcoplasmicreticulum exposes binding sites on actin:

Muscle contraction Muscle relaxation

Active transport of Ca+2 into sarcoplasmicreticulum, which requires ATP, makesmyosin binding sites unavailable.

Ca+2 binds to troponin

Tropomyosin pulled aside

ATP

Contraction cycle

PADP +

PADP + PADP +

Ca+2

Ca+2

PADP +

PADP + PADP +

PADP

PADP

ATP ATP ATP

PADP + PADP +

ATP

Tropomyosin

Troponin Thin filament

Thick filament

Ca+2

Binding sites onactin exposed

1 Relaxed muscle

Ca+2

PADP +Ca+2

2 Exposed binding sites on actin moleculesallow the muscle contraction cycle to occur

6 ATP splits, which provides power to “cock” the myosincross-bridges

3 Cross-bridges bind actin tomyosin

5 New ATP binds to myosin, releasing linkages 4 Cross-bridges pull thin filament (power stroke), ADP and P released from myosin

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The Sliding Filament Model of Muscle Contraction

• When sarcromeres shorten, thick and thin filaments slide past one another• H zones and I bands narrow• Z lines move closer together


Z line

(a)

Z line

Sarcomere

Contracting

Fully contracted

Relaxed

2

3

1

A band

Thinfilaments

Thickfilaments

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Cross Bridge Cycling


Actin monomers

Release of Ca+2 from sarcoplasmicreticulum exposes binding sites on actin:

Muscle contraction Muscle relaxation

Active transport of Ca+2 into sarcoplasmicreticulum, which requires ATP, makesmyosin binding sites unavailable.

Ca+2 binds to troponin

Tropomyosin pulled aside

ATP

Contraction cycle

PADP +

PADP + PADP +

Ca+2

Ca+2

PADP +

PADP + PADP +

PADP

PADP

ATP ATP ATP

PADP + PADP +

ATP

Tropomyosin

Troponin Thin filament

Thick filament

Ca+2

Binding sites onactin exposed

1 Relaxed muscle

Ca+2

PADP +Ca+2

2 Exposed binding sites on actin moleculesallow the muscle contraction cycle to occur

6 ATP splits, which provides power to “cock” the myosincross-bridges

3 Cross-bridges bind actin tomyosin

5 New ATP binds to myosin, releasing linkages 4 Cross-bridges pull thin filament (power stroke), ADP and P released from myosin

• Myosin cross-bridge attaches to actin binding site

• Myosin cross-bridge pulls thin filament

• ADP and phosphate released from myosin

• New ATP binds to myosin

• Linkage between actin and myosin cross-bridge break

• ATP splits

• Myosin cross-bridge goes back to original position

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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 (SR)

• Myosin and actin binding prevented

• Muscle fiber relaxes

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Energy Sources for Contraction

• Creatine phosphate – stores energy that quickly converts ADP to ATP

1) Creatine phosphate and 2) Cellular respiration


ADP

ATP

ATP

P

When cellular

Creatine

Creatine

ADP

ATP

ATP

P

is high

Creatine

Creatine

When cellular is low

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Oxygen Supply and Cellular Respiration

• Cellular respiration:• Anaerobic Phase

• Glycolysis• Occurs in cytoplasm• Produces little ATP

• Aerobic Phase• Citric acid cycle• Electron transport system• Occurs in the mitochondria• Produces most ATP • Myoglobin stores extra oxygen


ATP2Energy

Lactic acid

Glucose

ATPSynthesis of 34CO2 + H2O + Energy

Pyruvic acid

Heat

1

2

Mit

och

on

dri

aC

yto

sol

In the absence ofsufficient oxygen,glycolysis leads tolactic acidaccumulation.

Oxygen carried fromthe lungs byhemoglobin in redblood cells is storedin muscle cells bymyoglobin and isavailable to supportaerobic respiration.

Citric acidcycle

Electrontransport

chain

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Oxygen Debt

• Oxygen not available• Glycolysis continues• Pyruvic acid converted to lactic acid• Liver converts lactic acid to glucose

• Oxygen debt – amount of oxygen needed by liver cells to use the accumulated lactic acid to produce glucose


ATP

Glucose

Glycogen

Lactic acid

Pyruvic acid

Energy tosynthesize

Energyfrom

Glycolysis andlactic acid formation(in muscle)

Synthesis of glucosefrom lactic acid(in liver)

ATP

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Muscle Fatigue

• Inability to contract muscle

• Commonly caused from:• Decreased blood flow• Ion imbalances across the sarcolemma• Accumulation of lactic acid

• Cramp – sustained, involuntary muscle contraction

• Physiological vs. psychological fatigue

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Heat Production

• By-product of cellular respiration

• Muscle cells are major source of body heat

• Blood transports heat throughout body core

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9.4: Muscular Responses

• Muscle contraction can be observed by removing a single skeletal muscle fiber and connecting it to a device that senses and records changes in the overall length of the muscle fiber.

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Threshold Stimulus

• Threshold Stimulus• Minimal strength required to cause contraction

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Recording of a Muscle Contraction

• Recording a Muscle Contraction• Twitch

• Latent period• Period of contraction• Period of relaxation

• Refractory period• All-or-none response


Fo

rce

of

con

trac

tio

n

Time

Latentperiod

Period ofcontraction

Period ofrelaxation

Time ofstimulation

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Length-Tension RelationshipCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

(b) Overly shortened (c) Overly stretched

(a) Optimal length

Muscle fiber length

Fo

rce

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Summation

• Process by which individual twitches combine• Produces sustained contractions• Can lead to tetanic contractions


Time(c)

(b)

Fo

rce

of

con

trac

tio

n

(a)

Fo

rce

of

con

trac

tio

nF

orc

e o

fco

ntr

acti

on

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Recruitment of Motor Units

• Recruitment - increase in the number of motor units activated

• Whole muscle composed of many motor units

• More precise movements are produced with fewer muscle fibers within a motor unit

• As intensity of stimulation increases, recruitment of motor units continues until all motor units are activated

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Sustained Contractions

• Smaller motor units (smaller diameter axons) - recruited first

• Larger motor units (larger diameter axons) - recruited later

• Produce smooth movements

• Muscle tone – continuous state of partial contraction

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Types of Contractions

• Isotonic – muscle contracts and changes length

• Concentric – shortening contraction• Eccentric – lengthening contraction

• Isometric – muscle contracts but does not change length


Movement Movement

(a) Muscle contracts with force greater than resistance and shortens (concentric contraction)

(c) Muscle contracts but does not change length (isometric contraction)

(b) Muscle contracts with force less than resistance and lengthens (eccentric contraction)

Nomovement

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Fast Twitch and Slow Twitch Muscle Fibers

• Slow-twitch fibers (Type I)• Always oxidative• Resistant to fatigue• Red fibers • Most myoglobin• Good blood supply

• Fast-twitch glycolytic fibers (Type IIa)• White fibers (less myoglobin)• Poorer blood supply• Susceptible to fatigue

• Fast-twitch fatigue-resistant fibers (Type IIb)

• Intermediate fibers• Oxidative• Intermediate amount of myoglobin• Pink to red in color• Resistant to fatigue

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Use and Disuse of Skeletal Muscles

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9.5: Smooth Muscles

• Compared to skeletal muscle fibers, smooth muscle fibers are:

• Shorter• Single, centrally located nucleus• Elongated with tapering ends• Myofilaments randomly organized• Lack striations• Lack transverse tubules• Sarcoplasmic reticula (SR) not well developed

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Smooth Muscle Fibers

• Visceral Smooth Muscle• Single-unit smooth muscle• Sheets of muscle fibers• Fibers held together by gap junctions• Exhibit rhythmicity• Exhibit peristalsis• Walls of most hollow organs

• Multi-unit Smooth Muscle• Less organized• Function as separate units • Fibers function separately• Iris of eye• Walls of blood vessels

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Smooth Muscle Contraction

• Resembles skeletal muscle contraction in that:• Interaction between actin and myosin• Both use calcium and ATP• Both are triggered by membrane impulses

• Different from skeletal muscle contraction in that:• Smooth muscle lacks troponin• Smooth muscle uses calmodulin • Two neurotransmitters affect smooth muscle

• Acetlycholine (Ach) and norepinephrine (NE)• 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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9.6: 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

• Longer refractory period than skeletal muscle

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Characteristics of Muscle Tissue

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9.7: Skeletal Muscle Actions

• Skeletal muscles generate a great variety of body movements.

• The action of each muscle mostly depends upon the kind of joint it is associated with and the way the muscle is attached on either side of that joint.

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Body Movement

Four Basic Components of Levers:1. Rigid bar – bones2. Fulcrum – point on which bar moves; joint3. Object - moved against resistance; weight4. Force – supplies energy for movement; muscles


Resistance ForceForce

Fulcrum

Resistance

Fulcrum

(a) First-class lever

FulcrumForce Force

Resistance Resistance

Fulcrum

(b) Second-class lever

Force

Resistance Force

Fulcrum(c) Third-class lever

Resistance

Fulcrum

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Levers and MovementCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Radius

Resistance

Resistance

Fulcrum

Ulna

(a)

(b)

Fulcrum

Force

Force

Forearm movement

Biceps brachiicontracting muscle

Relaxedmuscle

Triceps brachiicontracting muscle

Relaxedmuscle

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Origin and Insertion

• Origin – immovable end• Insertion – movable end


Radius

Coracoid process

Origins ofbiceps brachii

Tendon oflong head

Tendon ofshort head

Bicepsbrachii

Insertion ofbiceps brachii

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Interaction of Skeletal Muscles

• Prime mover (agonist) – primarily responsible for movement• Synergists – assist prime mover• Antagonist – resist prime mover’s action and cause movement in the opposite direction of the prime mover• Fixators

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9.8: Major Skeletal MusclesCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Brachioradialis

Frontalis

Deltoid

Brachialis

Biceps brachii

Gracilis

Vastus medialis

Gastrocnemius

Soleus

Trapezius

Tibialis anterior

External oblique

Sartorius

Rectus femoris

Adductor longus

Vastus lateralis

Fibularis longus

Orbicularis oculiZygomaticusMasseterOrbicularis oris

Sternocleido-mastoid

Pectoralismajor

Serratusanterior

Rectusabdominis

Extensordigitorum longus

Tensorfasciaelatae

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Major Skeletal MusclesCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Gracilis

Rhomboid

Infraspinatus

Gluteus medius

Vastus lateralisSartorius

Soleus

Fibularis longus

Brachialis

Temporalis

Occipitalis

Semimembranosus

Sternocleidomastoid

Trapezius

Teres minor

Teres major

Biceps femoris

Semitendinosus

Gastrocnemius

Calcaneal tendon

Deltoid

Tricepsbrachii Latissimus

dorsiExternaloblique

Gluteusmaximus

Adductormagnus

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Muscles of Facial Expression

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Muscles of Mastication

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Muscles of Facial Expression and Mastication


Epicranial aponeurosisFrontalis

Occipitalis

Epicranius

Masseter

Sternocleidomastoid

Temporalis

Orbicularis oculi

Zygomaticus major

Zygomaticus minor

Buccinator

Orbicularis oris

Platysma

Buccinator

Medial pterygoid

Lateral pterygoid

Temporalis

(a)

(c)(b)

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Muscles That Move the Head and Vertebral Column

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Muscles That Move the Head and Vertebral Column


Iliocostalis lumborum

Quadratus lumborum

Spinalis thoracis

Iliocostalis thoracis

Spinalis cervicisSplenius capitis

Spinalis capitisSemispinalis capitisLongissimus capitis

Semispinalis capitis (cut)

Longissimus cervicis

Iliocostalis cervicis

Longissimus thoracis

Splenius capitis (cut)

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Muscles That Move the Pectoral Girdle

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Muscles That Move the Pectoral Girdle


Trapezius

Deltoid

Deltoid

Latissimus dorsi

Levator scapulaeSupraspinatusInfraspinatusTeres minorTeres major

Rhomboid majorRhomboid minor

(a)

(d)(c)(b)

Rhomboidminor

Rhomboidmajor

Latissimusdorsi

Trapezius

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Muscles That Move the Arm

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Muscles That Move the ArmCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Trapezius

Deltoid

Pectoralis major

External oblique

Aponeurosis of external oblique

Sternocleidomastoid

Pectoralis minor

Internal intercostal

Serratus anterior

Rectus abdominis

Internal oblique

Transversus abdominis

External intercostal

Linea alba(band of connective tissue)

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Muscles That Move the ArmCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Levator scapulae

Levator scapulae

Supraspinatus

Spine of scapula

DeltoidInfraspinatusTeres minor

Teres major

(a)

(d)(c)(b)

Supraspinatus

InfraspinatusTeres minor

Teres major

Long head oftriceps brachii

Lateral head oftriceps brachii

Tricepsbrachii

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Muscles That Move the Forearm

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Muscles That Move the Forearm


Deltoid

Clavicle

Subscapularis

Coracobrachialis

Brachialis

Subscapularis

Coracobrachialis

Brachialis

(a)

(c) (d)(b)

Short head ofbiceps brachii

Long head ofbiceps brachii

Medial borderof scapula

Biceps brachii(short and longheads)

Trapezius

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Muscles That Move the ForearmCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Biceps brachii

Brachialis

SupinatorPronator teresBrachioradialis

Flexor carpi radialisPalmaris longusFlexor carpi ulnaris

Flexor carpi ulnaris

Pronator quadratusFlexor retinaculum

Brachioradialis

Flexor carpi radialis

Pronator teres

Pronator quadratus

(a) (b)

(c) (d) (e)

Flexor digitorumsuperficialis

Extensor carpiradialis longus

Flexor digitorumsuperficialis

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Cross Section of the ForearmCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Abductor pollicis longus m.

Flexor pollicis longus m.

Radius

Pronator teres m.

Brachioradialis m.

Radial n.

Radial a.

Flexor carpi radialis m.

Extensor digitorum m.

Ulna

Ulnar n.

Ulnar a.

Flexor carpi ulnaris m.

Median n.

Palmaris longus m.

Anterior

Plane ofsection

Extensor carpiradialis brevis m.

Extensor carpiradialis longus m.

Extensor carpiulnaris m.

Extensor pollicislongus m.

Flexor digitorumprofundus m.

Flexor digitorumsuperficialis m.

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Muscles That Move the Hand

• Flexors (anterior) and extensors (posterior)

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Muscles That Move the Hand

Triceps brachii

Flexor carpi ulnaris

Extensor carpi ulnaris

Extensor digitorum

Extensor retinaculum

Brachioradialis

Extensor carpiradialis longusand brevis

(a)

(b) (c)

Extensor carpiradialis longus

Extensor carpiradialis brevis

Extensorcarpi ulnaris

Extensordigitorum


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Muscles of the Abdominal Wall

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Muscles of the Abdominal WallCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

(a)

(b) (c) (d)

External obliqueRectus abdominis

Internal oblique

Transversus abdominis

External oblique

Internal oblique Transversusabdominis

(e)

Internal oblique

Transversusabdominis

External oblique

Linea alba

Rectus abdominis

Peritoneum

Skin


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Muscles of the Pelvic Outlet

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Muscles of Pelvic OutletCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Scrotum

IschiocavernosusClitoris

Urethral orifice

Anus

Bulbospongiosus

Levator aniGluteus maximus

Penis

Anus

Coccyx

Rectum

Urethra

Symphysis pubis

Coccygeus

Urogenital diaphragm

Levator ani

(b)(a)

(c)

Vagina

External analsphincter

Superficialtransversusperinei

Vaginal orifice

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Muscles That Move the Thigh

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Psoas major

Psoas minorIliacus

Rectus femoris

Sartorius

Sartorius

Vastus lateralis Vastus intermedius

Patella

Adductor longus

Pectineus

Adductormagnus

GracilisVastus medialis

Gracilis

Adductor brevis Adductor longus

Adductor magnus

IliacusPsoas majorPsoas minor

(a) (b)

(c) (d) (e)

(f) (g)

Tensor fasciae latae

Quadriceps femoristendon (patellar tendon)

Patellarligament


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Gluteus medius

Gluteus medius

Gluteus maximus

Gluteus maximus

Biceps femorisIliotibial tract (band)

Vastus lateralis

Rectus femoris

Sartorius

Tensor fasciae latae

Gluteus minimusPiriformis

(a)

(b) (c) (d)


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Muscles That Move the Leg

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Adductor magnus

Gracilis

Semitendinosus

Semimembranosus

Semimembranosus

Sartorius

Gastrocnemius

Gluteus medius

Gluteus maximus

Biceps femoris

Semitendinosus

(a)

(b) (c)

Vastus lateraliscovered by fascia

Biceps femoris(short head)

Biceps femoris(long head)


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Gracilis m.

Semimembranosus m.Semitendinosus m.

Sartorius m.Vastus medialis m.

Rectus femoris m.Adipose tissue

Skin

Adductor magnus m.

Adductor longus m.Great saphenousv.Femoralv . and a.

Vastus intermedius m.

Shaft of femur

Sciatic n.

Vastus lateralis m.

Lateral Medial

Anterior

Long head ofbiceps femoris m.

Short head ofbiceps femoris m.

Planeofsection


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Muscles That Move the LegCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Semitendinosus

SemimembranosusGracilisSartorius

Gastrocnemius:

Medial headLateral head

Soleus

Calcaneal tendon

Flexor retinaculum

Calcaneus

Biceps femoris

Plantaris

Soleus

Gastrocnemius

(a)

(b) (c)

(d) (e)

Flexor digitorumlongus

Fibularretinacula

Fibularisbrevis

Fibularislongus

Iliotibial tract(band)

Flexor digitorumlongus

Tibialis posterior

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Muscles That Move the Foot

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Muscles That Move the FootCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fibularis longus

Fibularis brevis

Fibularis tertius

Patella

Patellar ligament

Gastrocnemius

Soleus

Extensor retinacula

(a)

(b) (c) (d)

Tibia

Tibialis anterior

Extensor digitorumlongus


Tibialis anterior

Extensorhallucislongus

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Muscles That Move the FootCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Biceps femoris

Gastrocnemius

SoleusFibularis longus

Fibularis longus

Calcaneal tendon

Head of fibula

Fibularis tertiusFibularis brevis Extensor retinacula

Fibularis brevis

(a)

(b) (c)

Vastus lateralis

Tibialis anterior


Fibularretinacula

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TMJ Syndrome

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9.9: Lifespan Changes

• Myoglobin, ATP, and creatine phosphate decline

• By age 80, half of muscle mass has atrophied

• Adipose cells and connective tissues replace muscle tissue

• Exercise helps to maintain muscle mass and function

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Important Points in Chapter 9:Outcomes to be Assessed

9.1: Introduction

List various outcomes of muscle action.

9.2: Structure of a Skeletal Muscle

Describe how connective tissue is a part of the structure of a skeletal muscle.

Name the major parts of a skeletal muscle fiber and describe the functions of each.

9.3: Skeletal Muscle Contraction

Describe the neural control of skeletal muscle contraction.

Identify the major events that occur during skeletal muscle fiber contraction.

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List the energy sources for skeletal muscle fiber contraction.

Describe how a muscle may become fatigued.

Describe oxygen debt.

9.4: Muscular Responses

Distinguish between fast and slow twitch muscle fibers.

Distinguish between a twitch and a sustained contraction.

Describe how exercise affects skeletal muscles.

Explain how various types of muscular contractions produce body movements and help maintain posture.

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9.5: Smooth Muscle

Distinguish between the structures and functions of multiunit smooth muscle and visceral smooth muscle.

Compare the contraction mechanisms of skeletal and smooth muscle fibers.

9.6: Cardiac Muscle

Compare the contraction mechanisms of skeletal and cardiac muscle fibers.

9.7: Skeletal Muscle Actions

Explain how the attachments, locations, and interactions of skeletal muscles make possible certain movements.

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9.8: Major Skeletal Muscles

Identify and locate the skeletal muscles of each body region and describe the action (s) of each muscle.

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Chapter 9 Muscular System

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