chapter 7 the muscular system. elsevier items and derived items © 2008, 2004 by mosby, inc., an...

Chapter 7Chapter 7The Muscular SystemThe Muscular System

Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 2

INTRODUCTIONINTRODUCTION

Muscular tissue enables the body and its Muscular tissue enables the body and its parts to moveparts to move Three types of muscle tissue exist in body (see Three types of muscle tissue exist in body (see

Chapter 3)Chapter 3) Movement caused by muscle cells (called Movement caused by muscle cells (called

fibersfibers) shortening, or contracting) shortening, or contracting Muscle movement occurs when chemical Muscle movement occurs when chemical

energy (obtained from food) is converted into energy (obtained from food) is converted into mechanical energymechanical energy


MUSCLE TISSUEMUSCLE TISSUE

Types of muscle tissue (Figure 7-1)Types of muscle tissue (Figure 7-1) Skeletal muscle—also called Skeletal muscle—also called striatedstriated or or

voluntary musclevoluntary muscle• Microscope reveals crosswise stripes or striationsMicroscope reveals crosswise stripes or striations• Contractions can be voluntarily controlledContractions can be voluntarily controlled

Cardiac muscle—composes bulk of heartCardiac muscle—composes bulk of heart• Cardiac muscle fibers branch frequentlyCardiac muscle fibers branch frequently• Characterized by unique dark bands called Characterized by unique dark bands called

intercalated disksintercalated disks• Interconnected nature of cardiac muscle fibers Interconnected nature of cardiac muscle fibers

allows heart to contract efficiently as a unitallows heart to contract efficiently as a unit


MUSCLE TISSUEMUSCLE TISSUE

Types of muscle tissue (cont.)Types of muscle tissue (cont.) Nonstriated muscle, or involuntary muscle—Nonstriated muscle, or involuntary muscle—

also called also called smoothsmooth or or visceral musclevisceral muscle• Lacks cross stripes or striations when seen under a Lacks cross stripes or striations when seen under a

microscope; appears smoothmicroscope; appears smooth

• Found in walls of hollow visceral structures such as Found in walls of hollow visceral structures such as digestive tract, blood vessels, and uretersdigestive tract, blood vessels, and ureters

• Contractions not under voluntary control; movement Contractions not under voluntary control; movement caused by contraction is involuntarycaused by contraction is involuntary

Function—all muscle fibers specialize in Function—all muscle fibers specialize in contraction (shortening)contraction (shortening)


STRUCTURE OF SKELETAL MUSCLESTRUCTURE OF SKELETAL MUSCLE

Composition—mainlyComposition—mainly striated muscle fibers and striated muscle fibers and connective tissueconnective tissue Most skeletal muscles extend from one bone across a joint Most skeletal muscles extend from one bone across a joint

to another boneto another bone Parts of a skeletal muscleParts of a skeletal muscle

• Origin—attachment to the bone that remains relatively Origin—attachment to the bone that remains relatively stationary or fixed when movement at the joint occursstationary or fixed when movement at the joint occurs

• Insertion—point of attachment to the bone that moves when Insertion—point of attachment to the bone that moves when a muscle contractsa muscle contracts

• Body—main part of the muscleBody—main part of the muscle Muscles attach to bone by tendons—strong cords of Muscles attach to bone by tendons—strong cords of

fibrous connective tissue; some tendons enclosed in fibrous connective tissue; some tendons enclosed in synovial-lined tubes and are lubricated by synovial fluid; synovial-lined tubes and are lubricated by synovial fluid; tubes called tubes called tendon sheathstendon sheaths

Bursae—small synovial-lined sacs containing a small Bursae—small synovial-lined sacs containing a small amount of synovial fluid; located between some tendons amount of synovial fluid; located between some tendons and underlying bonesand underlying bones


STRUCTURE OF SKELETAL MUSCLESTRUCTURE OF SKELETAL MUSCLE

Microscopic structure (Figure 7-3)Microscopic structure (Figure 7-3) Contractile cells called Contractile cells called fibersfibers—grouped into bundles—grouped into bundles Fibers contain thick myofilaments (containing the protein Fibers contain thick myofilaments (containing the protein

myosin) and thin myofilaments (composed of actin)myosin) and thin myofilaments (composed of actin) Basic functional (contractile) unit called Basic functional (contractile) unit called sarcomeresarcomere

• Sarcomeres separated from each other by dark bands Sarcomeres separated from each other by dark bands called called Z linesZ lines

• Sliding filament model explains mechanism of contractionSliding filament model explains mechanism of contraction Thick and thin myofilaments slide past each other as a Thick and thin myofilaments slide past each other as a

muscle contractsmuscle contracts Contraction requires calcium and energy-rich ATP moleculesContraction requires calcium and energy-rich ATP molecules


FUNCTIONS OF SKELETAL MUSCLEFUNCTIONS OF SKELETAL MUSCLE

MovementMovement Muscles produce movement; as a muscle Muscles produce movement; as a muscle

contracts, it pulls the insertion bone closer to contracts, it pulls the insertion bone closer to the origin bone; movement occurs at the joint the origin bone; movement occurs at the joint between the origin and the insertionbetween the origin and the insertion• Groups of muscles usually contract to produce a Groups of muscles usually contract to produce a

single movementsingle movement Prime mover—muscle whose contraction is mainly Prime mover—muscle whose contraction is mainly

responsible for producing a given movementresponsible for producing a given movement Synergist—muscle whose contractions help the prime Synergist—muscle whose contractions help the prime

mover produce a given movementmover produce a given movement Antagonist—muscle whose actions oppose the action Antagonist—muscle whose actions oppose the action

of a prime mover in any given movementof a prime mover in any given movement



PosturePosture A specialized type of muscle contraction, called A specialized type of muscle contraction, called tonic tonic

contractioncontraction, enables us to maintain body position, enables us to maintain body position• In tonic contraction, only a few of a muscle’s fibers shorten In tonic contraction, only a few of a muscle’s fibers shorten

at one timeat one time

• Tonic contractions produce no movement of body partsTonic contractions produce no movement of body parts

• Tonic contractions maintain muscle tone called Tonic contractions maintain muscle tone called postureposture Good posture reduces strain on muscles, tendons, ligaments, Good posture reduces strain on muscles, tendons, ligaments,

and bonesand bones Poor posture causes fatigue and may lead to deformityPoor posture causes fatigue and may lead to deformity



Heat productionHeat production Survival depends on the body’s ability to Survival depends on the body’s ability to

maintain a constant body temperaturemaintain a constant body temperature• Fever—an elevated body temperature—often a sign Fever—an elevated body temperature—often a sign

of illnessof illness

• Hypothermia—a reduced body temperatureHypothermia—a reduced body temperature

Contraction of muscle fibers produces most of Contraction of muscle fibers produces most of the heat required to maintain normal body the heat required to maintain normal body temperaturetemperature


FATIGUEFATIGUE

Reduced strength of muscle contractionReduced strength of muscle contraction Caused by repeated muscle stimulation Caused by repeated muscle stimulation

without adequate periods of restwithout adequate periods of rest Repeated muscular contraction depletes Repeated muscular contraction depletes

cellular ATP stores and outstrips the ability cellular ATP stores and outstrips the ability of the blood supply to replenish oxygen of the blood supply to replenish oxygen and nutrientsand nutrients


FATIGUEFATIGUE

Contraction in the absence of adequate Contraction in the absence of adequate oxygen produces lactic acid, which oxygen produces lactic acid, which contributes to muscle sorenesscontributes to muscle soreness

Oxygen debtOxygen debt—term used to describe the —term used to describe the metabolic effort required to burn excess metabolic effort required to burn excess lactic acid that may accumulate during lactic acid that may accumulate during prolonged periods of exercise; the body is prolonged periods of exercise; the body is attempting to return the cells’ energy and attempting to return the cells’ energy and oxygen reserves to pre-exercise levelsoxygen reserves to pre-exercise levels


ROLE OF OTHER BODY SYSTEMS IN ROLE OF OTHER BODY SYSTEMS IN MOVEMENTMOVEMENT

Muscle functioning depends on the functioning of Muscle functioning depends on the functioning of many other parts of the bodymany other parts of the body

Most muscles cause movements by pulling on Most muscles cause movements by pulling on bones across movable jointsbones across movable joints

Respiratory, circulatory, nervous, muscular, and Respiratory, circulatory, nervous, muscular, and skeletal systems play essential roles in producing skeletal systems play essential roles in producing normal movementsnormal movements

Multiple sclerosis, brain hemorrhage, and spinal Multiple sclerosis, brain hemorrhage, and spinal cord injury are examples of how pathological cord injury are examples of how pathological conditions in other body organ systems can conditions in other body organ systems can dramatically affect movementdramatically affect movement


MOTOR UNIT (Figure 7-4)MOTOR UNIT (Figure 7-4)

Stimulation of a muscle by a nerve impulse is Stimulation of a muscle by a nerve impulse is required before a muscle can shorten and required before a muscle can shorten and produce movementproduce movement

A motor neuron is the specialized nerve that A motor neuron is the specialized nerve that transmits an impulse to a muscle, causing transmits an impulse to a muscle, causing contractioncontraction

A neuromuscular junction is the specialized point A neuromuscular junction is the specialized point of contact between a nerve ending and the of contact between a nerve ending and the muscle fiber it innervatesmuscle fiber it innervates

A motor unit is the combination of a motor neuron A motor unit is the combination of a motor neuron with the muscle fiber or fibers it innervateswith the muscle fiber or fibers it innervates


MUSCLE STIMULUSMUSCLE STIMULUS

A muscle will contract only if an applied A muscle will contract only if an applied stimulus reaches a certain level of intensitystimulus reaches a certain level of intensity A threshold stimulus is the minimal level of A threshold stimulus is the minimal level of

stimulation required to cause a muscle fiber to stimulation required to cause a muscle fiber to contractcontract

Once stimulated by a threshold stimulus, a Once stimulated by a threshold stimulus, a muscle fiber will contract completely, a muscle fiber will contract completely, a response called response called all or noneall or none


MUSCLE STIMULUSMUSCLE STIMULUS

Different muscle fibers in a muscle are Different muscle fibers in a muscle are controlled by different motor units having controlled by different motor units having different threshold-stimulus levelsdifferent threshold-stimulus levels Although individual muscle fibers always Although individual muscle fibers always

respond all or none to a threshold stimulus, the respond all or none to a threshold stimulus, the muscle as a whole does notmuscle as a whole does not

Different motor units responding to different Different motor units responding to different threshold stimuli permit a muscle as a whole to threshold stimuli permit a muscle as a whole to execute contractions of graded forceexecute contractions of graded force


TYPES OF SKELETAL MUSCLE TYPES OF SKELETAL MUSCLE CONTRACTIONCONTRACTION

Twitch and tetanic contractionsTwitch and tetanic contractions Twitch contractions are laboratory phenomena Twitch contractions are laboratory phenomena

and do not play a significant role in normal and do not play a significant role in normal muscular activity; they are a single contraction muscular activity; they are a single contraction of muscle fibers caused by a single threshold of muscle fibers caused by a single threshold stimulusstimulus

Tetanic contractions are sustained and steady Tetanic contractions are sustained and steady muscular contractions caused by a series of muscular contractions caused by a series of stimuli bombarding a muscle in rapid stimuli bombarding a muscle in rapid successionsuccession



Isotonic contractionsIsotonic contractions Contraction of a muscle that produces movement at a Contraction of a muscle that produces movement at a

joint because the muscle changes lengthjoint because the muscle changes length During concentric contractions, the muscle shortens During concentric contractions, the muscle shortens

insertion end of the muscle to move toward the point of insertion end of the muscle to move toward the point of originorigin

During eccentric contractions, the muscle lengthens During eccentric contractions, the muscle lengthens under tension, thus moving the insertion away from the under tension, thus moving the insertion away from the originorigin

Most types of body movements such as walking and Most types of body movements such as walking and running are produced by isotonic contractionsrunning are produced by isotonic contractions



Isometric contractionsIsometric contractions Isometric contractions are muscle contractions Isometric contractions are muscle contractions

that do not produce movement; the muscle as that do not produce movement; the muscle as a whole does not shortena whole does not shorten

Although no movement occurs during isometric Although no movement occurs during isometric contractions, tension within the muscle contractions, tension within the muscle increasesincreases


EFFECTS OF EXERCISE ON EFFECTS OF EXERCISE ON SKELETAL MUSCLESSKELETAL MUSCLES

Exercise, if regular and properly practiced, Exercise, if regular and properly practiced, improves muscle tone and posture, results improves muscle tone and posture, results in more efficient heart and lung in more efficient heart and lung functioning, and reduces fatiguefunctioning, and reduces fatigue

Muscles change in relation to the amount Muscles change in relation to the amount of work they normally doof work they normally do Prolonged inactivity causes disuse atrophyProlonged inactivity causes disuse atrophy Regular exercise increases muscle size, called Regular exercise increases muscle size, called

hypertrophyhypertrophy


EFFECTS OF EXERCISE ON EFFECTS OF EXERCISE ON SKELETAL MUSCLESSKELETAL MUSCLES

Strength training is exercise involving contraction of Strength training is exercise involving contraction of muscles against heavy resistancemuscles against heavy resistance Strength training increases the number of myofilaments in Strength training increases the number of myofilaments in

each muscle fiber, and as a result, the total mass of the muscle each muscle fiber, and as a result, the total mass of the muscle increasesincreases

Strength training does not increase the number of muscle Strength training does not increase the number of muscle fibersfibers

Endurance training is exercise that increases a muscle’s Endurance training is exercise that increases a muscle’s ability to sustain moderate exercise over a long period; it is ability to sustain moderate exercise over a long period; it is sometimes called sometimes called aerobic trainingaerobic training Endurance training allows more efficient delivery of oxygen and Endurance training allows more efficient delivery of oxygen and

nutrients to a muscle via increased blood flownutrients to a muscle via increased blood flow Endurance training does not usually result in muscle Endurance training does not usually result in muscle

hypertrophyhypertrophy


SKELETAL MUSCLE GROUPS SKELETAL MUSCLE GROUPS (Table 7-1)(Table 7-1)

Muscles of the head and neck (Figure 7-7)Muscles of the head and neck (Figure 7-7) Facial musclesFacial muscles

• Orbicularis oculiOrbicularis oculi• Orbicularis orisOrbicularis oris• ZygomaticusZygomaticus

Muscles of masticationMuscles of mastication• MasseterMasseter• TemporalTemporal

Sternocleidomastoid—flexes headSternocleidomastoid—flexes head Trapezius—elevates shoulders and extends Trapezius—elevates shoulders and extends

headhead


SKELETAL MUSCLE GROUPSSKELETAL MUSCLE GROUPS

Muscles that move the upper extremitiesMuscles that move the upper extremities Pectoralis major—flexes upper armPectoralis major—flexes upper arm Latissimus dorsi—extends upper armLatissimus dorsi—extends upper arm Deltoid—abducts upper armDeltoid—abducts upper arm Biceps brachii—flexes forearmBiceps brachii—flexes forearm Triceps brachii—extends forearmTriceps brachii—extends forearm



Muscles of the trunk (Figure 7-8)Muscles of the trunk (Figure 7-8) Abdominal musclesAbdominal muscles

• Rectus abdominisRectus abdominis

• External obliqueExternal oblique

• Internal obliqueInternal oblique

• Transversus abdominisTransversus abdominis

Respiratory musclesRespiratory muscles• Intercostal musclesIntercostal muscles

• DiaphragmDiaphragm



Muscles that move the lower extremitiesMuscles that move the lower extremities Iliopsoas—flexes thighIliopsoas—flexes thigh Gluteus maximus—extends thighGluteus maximus—extends thigh Adductor muscles—adduct thighsAdductor muscles—adduct thighs Hamstring muscles—flex lower legHamstring muscles—flex lower leg

• SemimembranosusSemimembranosus• SemitendinosusSemitendinosus• Biceps femorisBiceps femoris

Quadriceps femoris group—extend lower legQuadriceps femoris group—extend lower leg• Rectus femorisRectus femoris• Vastus musclesVastus muscles

Tibialis anterior—dorsiflexes footTibialis anterior—dorsiflexes foot Gastrocnemius—plantar flexes footGastrocnemius—plantar flexes foot Peroneus group—flex footPeroneus group—flex foot


MOVEMENTS PRODUCED BY MOVEMENTS PRODUCED BY SKELETAL MUSCLE CONTRACTIONS SKELETAL MUSCLE CONTRACTIONS

(Figures 7-9 through 7-11)(Figures 7-9 through 7-11) Flexion—movement that decreases the angle Flexion—movement that decreases the angle

between two bones at their joint: bendingbetween two bones at their joint: bending Extension—movement that increases the angle Extension—movement that increases the angle

between two bones at their joint: straighteningbetween two bones at their joint: straightening Abduction—movement of a part away from the Abduction—movement of a part away from the

midline of the bodymidline of the body Adduction—movement of a part toward the Adduction—movement of a part toward the

midline of the bodymidline of the body Rotation—movement around a longitudinal axisRotation—movement around a longitudinal axis


MOVEMENTS PRODUCED BY MOVEMENTS PRODUCED BY SKELETAL MUSCLE CONTRACTIONSSKELETAL MUSCLE CONTRACTIONS

Supination and pronation—hand positions that Supination and pronation—hand positions that result from rotation of the forearm; supination result from rotation of the forearm; supination results in a hand position with the palm turned to results in a hand position with the palm turned to the anterior position; pronation occurs when the the anterior position; pronation occurs when the palm faces posteriorlypalm faces posteriorly

Dorsiflexion and plantar flexion—foot movements; Dorsiflexion and plantar flexion—foot movements; dorsiflexion results in elevation of the dorsum or dorsiflexion results in elevation of the dorsum or top of the foot; during plantar flexion, the bottom top of the foot; during plantar flexion, the bottom of the foot is directed downwardof the foot is directed downward

Inversion and eversion—foot movements; Inversion and eversion—foot movements; inversion moves ankle to side so that sole faces inversion moves ankle to side so that sole faces inward toward midline; eversion turns ankle so inward toward midline; eversion turns ankle so that the sole faces out to the sidethat the sole faces out to the side

chapter 7 the muscular system. elsevier items and derived items © 2008, 2004 by mosby, inc., an...

Documents

derived items

affiliate of elsevier

unitelsevier items

muscle cells

nonstriated muscle

muscle contractscontraction

muscle contractsbodymain

underlying boneselsevier