Bell RingerBell Ringer

• List ten different uses of musclesList ten different uses of muscles

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Chapter 6Chapter 6

Muscular Muscular SystemSystem

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The Muscular SystemThe Muscular System

• Muscles are responsible for all types Muscles are responsible for all types of body movementof body movement

• Three basic muscle types are found Three basic muscle types are found in the bodyin the body– Skeletal muscleSkeletal muscle– Cardiac muscleCardiac muscle– Smooth muscleSmooth muscle

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Characteristics of MusclesCharacteristics of Muscles

• Muscle cells are elongated Muscle cells are elongated (muscle cell = muscle fiber)(muscle cell = muscle fiber)

• Contraction of muscles is due to the Contraction of muscles is due to the movement of microfilamentsmovement of microfilaments

• All muscles share some terminologyAll muscles share some terminology– Prefix Prefix myomyo refers to muscle refers to muscle– Prefix Prefix mysmys refers to muscle refers to muscle– Prefix Prefix sarcosarco refers to flesh refers to flesh

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Skeletal Muscle CharacteristicsSkeletal Muscle Characteristics

• Most are attached by tendons to Most are attached by tendons to bonesbones

• Cells are multinucleateCells are multinucleate• Striated – have visible bandingStriated – have visible banding• Voluntary – subject to conscious Voluntary – subject to conscious

controlcontrol• Cells are surrounded and bundled by Cells are surrounded and bundled by

connective tissueconnective tissue

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Connective Tissue Connective Tissue

Wrappings of Skeletal Wrappings of Skeletal MuscleMuscle

• Endomysium – Endomysium – around single around single muscle fibermuscle fiber

• Perimysium – Perimysium – around a fascicle around a fascicle (bundle) of fibers(bundle) of fibers

Figure 6.16

Connective Tissue Wrappings Connective Tissue Wrappings of Skeletal Muscleof Skeletal Muscle

• Epimysium – Epimysium – covers the entire covers the entire skeletal muscleskeletal muscle

• Fascia – on the Fascia – on the outside of the outside of the epimysiumepimysium

Figure 6.17

Skeletal Muscle Skeletal Muscle AttachmentsAttachments

• Epimysium blends into a connective Epimysium blends into a connective tissue attachmenttissue attachment– Tendon – cord-like structureTendon – cord-like structure– Aponeuroses – sheet-like structureAponeuroses – sheet-like structure

• Sites of muscle attachmentSites of muscle attachment– BonesBones– CartilagesCartilages– Connective tissue coveringsConnective tissue coverings

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Smooth Muscle CharacteristicsSmooth Muscle Characteristics

• Has no striationsHas no striations• Spindle-shaped Spindle-shaped

cellscells• Single nucleusSingle nucleus• Involuntary – no Involuntary – no

conscious controlconscious control• Found mainly in Found mainly in

the walls of the walls of hollow organshollow organs

Figure 6.2a9

Cardiac Muscle Cardiac Muscle CharacteristicsCharacteristics

• Has striationsHas striations• Usually has a Usually has a

single nucleussingle nucleus• Joined to another Joined to another

muscle cell at an muscle cell at an intercalated discintercalated disc

• InvoluntaryInvoluntary• Found only in the Found only in the

heartheartFigure 6.2b10

Function of MusclesFunction of Muscles

• Produce movementProduce movement• Maintain postureMaintain posture• Stabilize jointsStabilize joints• Generate heatGenerate heat

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Properties of Skeletal Properties of Skeletal Muscle ActivityMuscle Activity

• Irritability – ability to receive and Irritability – ability to receive and respond to a stimulusrespond to a stimulus

• Contractility – ability to shorten when Contractility – ability to shorten when an adequate stimulus is receivedan adequate stimulus is received

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Nerve Stimulus to MusclesNerve Stimulus to Muscles

• Skeletal muscles Skeletal muscles must be must be stimulated by a stimulated by a nerve to nerve to contractcontract

• Motor unitMotor unit– One neuronOne neuron– Muscle cells Muscle cells

stimulated by stimulated by that neuronthat neuron

Figure 6.4a13

Contraction of a Skeletal Contraction of a Skeletal MuscleMuscle

• Muscle fiber contraction is “all or none”Muscle fiber contraction is “all or none”• Within a skeletal muscle, not all fibers Within a skeletal muscle, not all fibers

may be stimulated during the same may be stimulated during the same intervalinterval

• Different combinations of muscle fiber Different combinations of muscle fiber contractions may give differing contractions may give differing responsesresponses

• Graded responses – different degrees Graded responses – different degrees of skeletal muscle shorteningof skeletal muscle shortening

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Muscle Response to Strong Muscle Response to Strong StimuliStimuli

• Muscle force depends upon the Muscle force depends upon the number of fibers stimulatednumber of fibers stimulated

• More fibers contracting results in More fibers contracting results in greater muscle tensiongreater muscle tension

• Muscles can continue to contract Muscles can continue to contract unless they run out of energyunless they run out of energy

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Bell RingerBell Ringer

• What are the three types of muscle What are the three types of muscle cells and give how they differ in cells and give how they differ in three ways. Give detailthree ways. Give detail

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Energy for Muscle Energy for Muscle ContractionContraction

• Initially, muscles used stored ATP for Initially, muscles used stored ATP for energyenergy– Bonds of ATP are broken to release Bonds of ATP are broken to release

energyenergy– Only 4-6 seconds worth of ATP is stored Only 4-6 seconds worth of ATP is stored

by musclesby muscles

• After this initial time, other pathways After this initial time, other pathways must be utilized to produce ATPmust be utilized to produce ATP

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Energy for Muscle Energy for Muscle ContractionContraction

• Direct phosphorylationDirect phosphorylation– Muscle cells contain Muscle cells contain

creatine phosphate (CP)creatine phosphate (CP)• CP is a high-energy CP is a high-energy

moleculemolecule

– After ATP is depleted, After ATP is depleted, ADP is leftADP is left

– CP transfers energy to CP transfers energy to ADP, to regenerate ATPADP, to regenerate ATP

– CP supplies are CP supplies are exhausted in about 20 exhausted in about 20 secondsseconds

Figure 6.10a18

Energy for Muscle Energy for Muscle ContractionContraction

• Aerobic RespirationAerobic Respiration– Series of metabolic Series of metabolic

pathways that occur in pathways that occur in the mitochondriathe mitochondria

– Glucose is broken down Glucose is broken down to carbon dioxide and to carbon dioxide and water, releasing energywater, releasing energy

– This is a slower reaction This is a slower reaction that requires continuous that requires continuous oxygenoxygen

Figure 6.10b19

Energy for Muscle ContractionEnergy for Muscle Contraction

• Anaerobic glycolysisAnaerobic glycolysis– Reaction that breaks Reaction that breaks

down glucose without down glucose without oxygenoxygen

– Glucose is broken Glucose is broken down to pyruvic acid down to pyruvic acid to produce some ATPto produce some ATP

– Pyruvic acid is Pyruvic acid is converted to lactic converted to lactic acidacid

Figure 6.10c20

Energy for Muscle Energy for Muscle ContractionContraction

• Anaerobic glycolysis Anaerobic glycolysis (continued)(continued)– This reaction is not as This reaction is not as

efficient, but is fastefficient, but is fast• Huge amounts of Huge amounts of

glucose are neededglucose are needed• Lactic acid produces Lactic acid produces

muscle fatiguemuscle fatigue

Figure 6.10c21

Bell RingerBell Ringer

• List the seven criteria for naming muscles.

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Muscle Fatigue and Oxygen Muscle Fatigue and Oxygen DebtDebt

• When a muscle is fatigued, it is unable to When a muscle is fatigued, it is unable to contractcontract

• The common reason for muscle fatigue The common reason for muscle fatigue is oxygen debtis oxygen debt– Oxygen must be “repaid” to tissue to Oxygen must be “repaid” to tissue to

remove oxygen debtremove oxygen debt– Oxygen is required to get rid of accumulated Oxygen is required to get rid of accumulated

lactic acidlactic acid• Increasing acidity (from lactic acid) and Increasing acidity (from lactic acid) and

lack of ATP causes the muscle to lack of ATP causes the muscle to contract lesscontract less

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Types of Muscle Types of Muscle ContractionsContractions

• Isotonic contractionsIsotonic contractions– Myofilaments are able to slide past each Myofilaments are able to slide past each

other during contractionsother during contractions– The muscle shortensThe muscle shortens

• Isometric contractionsIsometric contractions– Tension in the muscles increasesTension in the muscles increases– The muscle is unable to shortenThe muscle is unable to shorten

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Muscle ToneMuscle Tone

• Some fibers are contracted even in a Some fibers are contracted even in a relaxed musclerelaxed muscle

• Different fibers contract at different Different fibers contract at different times to provide muscle tonetimes to provide muscle tone

• The process of stimulating various The process of stimulating various fibers is under involuntary controlfibers is under involuntary control

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Muscles and Body Muscles and Body MovementsMovements

• Movement is Movement is attained due to a attained due to a muscle moving muscle moving an attached bonean attached bone

Figure 6.1226

Muscles and Body Muscles and Body MovementsMovements

• Muscles are Muscles are attached to at attached to at least two pointsleast two points– Origin – Origin –

attachment to a attachment to a immoveable boneimmoveable bone

– Insertion – Insertion – attachment to an attachment to an movable bonemovable bone

Figure 6.1227

Effects of Exercise on Effects of Exercise on MuscleMuscle

• Results of increased muscle useResults of increased muscle use– Increase in muscle sizeIncrease in muscle size– Increase in muscle strengthIncrease in muscle strength– Increase in muscle efficiencyIncrease in muscle efficiency– Muscle becomes more fatigue resistantMuscle becomes more fatigue resistant

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Types of Ordinary Body Types of Ordinary Body MovementsMovements

• FlexionFlexion• ExtensionExtension• RotationRotation• AbductionAbduction• CircumductionCircumduction

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Special MovementsSpecial Movements

• DorsiflexionDorsiflexion• Plantar flexionPlantar flexion• InversionInversion• EversionEversion• SupinationSupination• PronationPronation• OppositionOpposition

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Types of MusclesTypes of Muscles

• Prime mover – muscle with the major Prime mover – muscle with the major responsibility for a certain movementresponsibility for a certain movement

• Antagonist – muscle that opposes or Antagonist – muscle that opposes or reverses a prime moverreverses a prime mover

• Synergist – muscle that aids a prime Synergist – muscle that aids a prime mover in a movement and helps mover in a movement and helps prevent rotationprevent rotation

• Fixator – stabilizes the origin of a Fixator – stabilizes the origin of a prime moverprime mover

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Naming of Skeletal MusclesNaming of Skeletal Muscles

• Direction of muscle fibersDirection of muscle fibers– Example: Example: rectusrectus (straight) (straight)

• Relative size of the muscleRelative size of the muscle– Example: Example: maximusmaximus (largest) (largest)

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Naming of Skeletal MusclesNaming of Skeletal Muscles

• Location of the muscleLocation of the muscle– Example: many muscles are named for Example: many muscles are named for

bones (e.g., bones (e.g., temporalistemporalis))

• Number of originsNumber of origins– Example: Example: tricepstriceps (three heads) (three heads)

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Naming of Skeletal Muscles

• Location of the muscle’s origin and Location of the muscle’s origin and insertioninsertion– Example: Example: sternosterno (on the sternum) (on the sternum)

• Shape of the muscleShape of the muscle– Example: Example: deltoiddeltoid (triangular) (triangular)

• Action of the muscleAction of the muscle– Example: Example: flexorflexor and and extensorextensor (flexes or (flexes or

extends a bone)extends a bone)

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Trunk MusclesTrunk Muscles

Figure 6.1635

Deep Trunk and Arm Deep Trunk and Arm MusclesMuscles

Figure 6.1736

Muscles of the Pelvis, Hip, Muscles of the Pelvis, Hip, and Thighand Thigh

Figure 6.19c37

Muscles of the Lower LegMuscles of the Lower Leg

Figure 6.2038

Superficial Muscles: AnteriorSuperficial Muscles: Anterior

Figure 6.2139

Superficial Muscles: Superficial Muscles: PosteriorPosterior

Figure 6.2240