ch. 8 the muscular system i’m only 73 yrs. young!

Ch. 8 Ch. 8 The Muscular The Muscular

SystemSystem

I’m only 73 yrs. Young!

The Muscular SystemThe Muscular SystemMuscles are Muscles are responsible for all types responsible for all types of body movementof body movementThree basic muscle Three basic muscle types are found in the types are found in the bodybody

–Skeletal muscleSkeletal muscle–Cardiac muscleCardiac muscle–Smooth muscleSmooth muscle

Characteristics of MusclesCharacteristics of MusclesMuscle cells are elongated Muscle cells are elongated (muscle cell = muscle fiber)(muscle cell = muscle fiber)

Contraction of muscles is Contraction of muscles is due to the movement of due to the movement of microfilamentsmicrofilaments

All muscles share some All muscles share some terminologyterminology– 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

Skeletal Muscle CharacteristicsSkeletal Muscle Characteristics

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

Skeletal Muscle CharacteristicsSkeletal Muscle CharacteristicsCells are multinucleateCells are multinucleate

StriatedStriated – have visible banding – have visible banding

VoluntaryVoluntary – subject to conscious control – subject to conscious control

Cells are surrounded and bundled by Cells are surrounded and bundled by connective tissueconnective tissue

Connective Tissue Wrappings of Connective Tissue Wrappings of Skeletal MuscleSkeletal Muscle

Epimysium – Epimysium – covers the covers the entire skeletal entire skeletal musclemuscle

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

Connective Tissue Wrappings of Connective Tissue Wrappings of Skeletal MuscleSkeletal Muscle

Endomysium – Endomysium – around single around single muscle fibermuscle fiber

Perimysium – Perimysium – around a around a fascicle fascicle (bundle) of (bundle) of fibersfibers

Skeletal Muscle AttachmentsSkeletal Muscle AttachmentsEpimysium blends into a Epimysium blends into a connective tissue connective tissue attachmentattachment– Tendon – cord-like structureTendon – cord-like structure– Aponeuroses – sheet-like Aponeuroses – sheet-like

structurestructure

Sites of muscle Sites of muscle attachmentattachment– BonesBones– CartilagesCartilages– Connective tissue coveringsConnective tissue coverings

Smooth Muscle CharacteristicsSmooth Muscle CharacteristicsHas 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 hollow the walls of hollow organsorgans

Cardiac Muscle CharacteristicsCardiac Muscle CharacteristicsHas 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 heartheart

Function of MusclesFunction of MusclesProduce Produce movementmovement

Maintain postureMaintain posture

Stabilize jointsStabilize joints

Generate heatGenerate heat

Microscopic Anatomy of Skeletal Microscopic Anatomy of Skeletal MuscleMuscle

Cells are multinucleateCells are multinucleate

Nuclei are just beneath the Nuclei are just beneath the sarcolemmasarcolemma


Sarcolemma – specialized plasma Sarcolemma – specialized plasma membranemembrane

Sarcoplasmic reticulum – specialized Sarcoplasmic reticulum – specialized smooth endoplasmic reticulumsmooth endoplasmic reticulum


MyofibrilMyofibril– Bundles of myofilamentsBundles of myofilaments– Myofibrils are aligned to give distinct Myofibrils are aligned to give distinct

bandsbandsI band =I band =

light bandlight band

A band = A band = dark banddark band


SarcomereSarcomere– Contractile unit of a muscle fiberContractile unit of a muscle fiber


Organization of the sarcomereOrganization of the sarcomere– Thick filaments = myosin filamentsThick filaments = myosin filaments

Composed of the protein myosinComposed of the protein myosin

Has ATPase enzymesHas ATPase enzymes


Organization of the sarcomereOrganization of the sarcomere– Thin filaments = actin filamentsThin filaments = actin filaments

Composed of the protein actinComposed of the protein actin


Myosin filaments have heads Myosin filaments have heads (extensions, or cross bridges)(extensions, or cross bridges)

Myosin and Myosin and actin overlap actin overlap somewhatsomewhat


At rest, there is a bare zone that At rest, there is a bare zone that lacks actin filamentslacks actin filaments

Sarcoplasmic Sarcoplasmic reticulum reticulum (SR) – for (SR) – for storage of storage of calciumcalcium

Nerve Stimulus to MusclesNerve Stimulus to MusclesSkeletal muscles Skeletal muscles must be must be stimulated by a stimulated by a nerve to contractnerve to contract

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

stimulated by that stimulated by that neuronneuron

Nerve Stimulus to MusclesNerve Stimulus to MusclesNeuromuscular junctions – Neuromuscular junctions – association site of nerve and muscleassociation site of nerve and muscle

Nerve Stimulus to MusclesNerve Stimulus to MusclesSynaptic cleft – Synaptic cleft – gap between nerve gap between nerve and muscleand muscle– Nerve and muscle Nerve and muscle

do not make do not make contactcontact

– Area between Area between nerve and muscle nerve and muscle is filled with is filled with interstitial fluidinterstitial fluid

Transmission of Nerve Impulse to Transmission of Nerve Impulse to MuscleMuscle

Neurotransmitter – chemical released Neurotransmitter – chemical released by nerve upon arrival of nerve by nerve upon arrival of nerve impulseimpulse– The neurotransmitter for skeletal muscle The neurotransmitter for skeletal muscle

is acetylcholineis acetylcholine

Neurotransmitter attaches to Neurotransmitter attaches to receptors on the sarcolemmareceptors on the sarcolemma

Sarcolemma becomes permeable to Sarcolemma becomes permeable to sodium (Nasodium (Na++))

Transmission of Nerve Impulse to Transmission of Nerve Impulse to MuscleMuscle

Sodium rushing into the cell Sodium rushing into the cell generates an action potentialgenerates an action potential

Once started, muscle contraction Once started, muscle contraction cannot be stoppedcannot be stopped

The Sliding Filament Theory of The Sliding Filament Theory of Muscle ContractionMuscle Contraction

Activation by nerve Activation by nerve causes myosin causes myosin heads heads (crossbridges) to (crossbridges) to attach to binding attach to binding sites on the thin sites on the thin filamentfilamentMyosin heads then Myosin heads then bind to the next site bind to the next site of the thin filamentof the thin filament

The Sliding Filament Theory of The Sliding Filament Theory of Muscle ContractionMuscle Contraction

This continued This continued action causes a action causes a sliding of the sliding of the myosin along the myosin along the actinactin

The result is that The result is that the muscle is the muscle is shortened shortened (contracted)(contracted)

The Sliding Filament TheoryThe Sliding Filament Theory

Contraction of a Skeletal MuscleContraction of a Skeletal MuscleMuscle fiber contraction is “all or none”Muscle fiber contraction is “all or none”

Within a skeletal muscle, not all fibers may Within a skeletal muscle, not all fibers may be stimulated during the same intervalbe stimulated during the same interval

Different combinations of muscle fiber Different combinations of muscle fiber contractions may give differing responsescontractions may give differing responses

Graded responses – different degrees of Graded responses – different degrees of skeletal muscle shorteningskeletal muscle shortening

Types of Graded ResponsesTypes of Graded Responses

TwitchTwitch– Single, brief contractionSingle, brief contraction– Not a normal muscle functionNot a normal muscle function


Tetanus (summing of contractions)Tetanus (summing of contractions)– One contraction is immediately followed One contraction is immediately followed

by anotherby another– The muscle does The muscle does

not completely not completely return to a return to a resting stateresting state

– The effects The effects are addedare added

Types of Graded ResponsesTypes of Graded ResponsesUnfused (incomplete) tetanusUnfused (incomplete) tetanus– Some relaxation occurs between Some relaxation occurs between

contractionscontractions– The results are summedThe results are summed


Fused (complete) tetanusFused (complete) tetanus– No evidence of relaxation before the No evidence of relaxation before the

following contractionsfollowing contractions– The result is a sustained muscle The result is a sustained muscle

contractioncontraction

Energy for Muscle ContractionEnergy for Muscle Contraction

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

Muscle Fatigue and Oxygen DebtMuscle Fatigue and Oxygen DebtWhen a muscle is fatigued, it is unable to When a muscle is fatigued, it is unable to contractcontract

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

oxygen debtoxygen 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 contract lack of ATP causes the muscle to contract lessless

Muscle ToneMuscle ToneSome 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

Muscles and Body MovementsMuscles and Body Movements

Movement is Movement is attained due to a attained due to a muscle moving an muscle moving an attached boneattached bone

Muscles and Body MovementsMuscles and Body MovementsMuscles are attached Muscles are attached to at least two pointsto at least two points– Origin – attachment to Origin – attachment to

a moveable bonea moveable bone– Insertion – attachment Insertion – attachment

to an immovable boneto an immovable bone

Five Golden Rules of Gross Five Golden Rules of Gross Muscle ActivityMuscle Activity

1.1. All muscles cross at least one jointAll muscles cross at least one joint

2.2. The bulk of muscles lies proximal to The bulk of muscles lies proximal to the joint crossedthe joint crossed

3.3. All muscles have at least 2 All muscles have at least 2 attachments: attachments: origin & insertionorigin & insertion

4.4. Muscles only pull/never pushMuscles only pull/never push

5.5. During contraction, the muscle During contraction, the muscle insertion moves toward the origininsertion moves toward the origin

Effects of Exercise on MuscleEffects of Exercise on MuscleAerobics result in stronger Aerobics result in stronger muscles due to increase muscles due to increase blood supply blood supply

Muscle fibers increase Muscle fibers increase mitochondria and oxygen mitochondria and oxygen storage storage Muscle becomes more fatigue resistant

Heart enlarges to pump more Heart enlarges to pump more blood to bodyblood to body

Does not increase skeletal Does not increase skeletal muscle sizemuscle size

Resistance training Resistance training results in the results in the increase of muscle increase of muscle size & strengthsize & strength

Individual muscle Individual muscle cells make more cells make more contractile filaments contractile filaments & connective tissue & connective tissue increasesincreases

Effects of Exercise on MuscleEffects of Exercise on Muscle

Types of Ordinary Body Types of Ordinary Body MovementsMovements

FlexionFlexion

ExtensionExtension

RotationRotation

AbductionAbduction

CircumductionCircumduction

Body MovementsBody Movements

Types of MusclesTypes of MusclesPrime 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 prevent mover in a movement and helps prevent rotationrotation

Fixator – stabilizes the origin of a prime Fixator – stabilizes the origin of a prime movermover

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)


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)


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)

Head and Neck MusclesHead and Neck Muscles

Trunk MusclesTrunk Muscles

Deep Trunk and Arm MusclesDeep Trunk and Arm Muscles

Muscles of Muscles of the Pelvis, the Pelvis, Hip, and Hip, and

ThighThigh

Muscles of Muscles of the Lower the Lower

LegLeg

Superficial Superficial Muscles: Muscles: AnteriorAnterior

Superficial Superficial Muscles: Muscles: PosteriorPosterior

Muscular DystrophyMuscular DystrophyCongenital muscle-destroying disease Congenital muscle-destroying disease affect specific muscle groupsaffect specific muscle groups

Muscle fibers degenerate & atrophy Muscle fibers degenerate & atrophy due to an absence of dystrophin, a due to an absence of dystrophin, a protein that helps keep muscle cells protein that helps keep muscle cells intactintact

Most common & serious—Duchenne’s Most common & serious—Duchenne’s M.D.M.D.– Mostly in males Mostly in males (diagnosed between 2-6 yrs)(diagnosed between 2-6 yrs)– Survival is rare beyond early 30’sSurvival is rare beyond early 30’s– X-linked recessiveX-linked recessive

Myasthenia gravisMyasthenia gravisRare adult disease caused by Rare adult disease caused by antibodies to acetylcholine antibodies to acetylcholine receptors at the neuromuscular receptors at the neuromuscular junction which prevents the junction which prevents the muscle contraction from muscle contraction from occurring occurring

Drooping upper eyelids, Drooping upper eyelids, difficulty swallowing & talking, difficulty swallowing & talking, muscle weakness & fatiguemuscle weakness & fatigue

Death occurs when respiratory Death occurs when respiratory muscles cease to functionmuscles cease to function

AgingAgingConnective Tissue Connective Tissue increasesincreases

Amount of Muscle tissue Amount of Muscle tissue decreasesdecreases

Muscles become Muscles become stringier(sinewy)stringier(sinewy)

Body weight declines due Body weight declines due to loss of muscle massto loss of muscle mass

By age 80, muscle strength By age 80, muscle strength usually decrease by 50% usually decrease by 50% without weight training without weight training exercisesexercises

ch. 8 the muscular system i’m only 73 yrs. young!

Documents

single muscle fiberperimysium

elongated muscle cell

entire skeletal musclefascia

musclenerve stimulus

actin filamentscomposed

neuronnerve stimulus

sarcomerethick filaments

sarcomerethin filaments