MuscularMuscular SystemSystem

FunctionsFunctions

Voluntary MovementVoluntary Movement

Maintain PostureMaintain Posture

Maintains normal body temperatureMaintains normal body temperature

Generates 85% of body heatGenerates 85% of body heat

Compensates for cold by Compensates for cold by shiveringshivering

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SkeletalSkeletal

SmoothSmooth

SkeletalSkeletal

CardiacCardiac

Muscle Cell CharacteristicsMuscle Cell CharacteristicsSkeletalSkeletal

VoluntaryVoluntaryAttached to bonesAttached to bonesCylindricalCylindricalStriatedStriatedMulti-nucleatedMulti-nucleatedNuclei near Nuclei near membranemembraneTight JunctionsTight JunctionsForm Motor UnitsForm Motor Units

CardiacCardiacInvoluntaryInvoluntaryHeartHeartCylindrical/BranchedCylindrical/BranchedStriatedStriatedSingle NucleusSingle NucleusCentral NucleusCentral NucleusGap Junctions – Gap Junctions – intercalated discsintercalated discsFigure 8 shapedFigure 8 shapedPacemakerPacemaker

Muscle Cell CharacteristicsMuscle Cell CharacteristicsSmooth MuscleSmooth Muscle

InvoluntaryInvoluntarySurrounding walls Surrounding walls of hollow organs of hollow organs and glandsand glandsSpindle shapedSpindle shapedNot striatedNot striatedSingle nucleusSingle nucleusCentral nucleusCentral nucleusGap JunctionsGap JunctionsSingle and Multi-Single and Multi-unitunit

Muscle Cell AnatomyMuscle Cell AnatomyMyofiber – muscle cellMyofiber – muscle cell

Sarcolemma – specialized cell Sarcolemma – specialized cell membrane of muscle cell (actively membrane of muscle cell (actively transports Natransports Na++ and K and K++

Sarcoplasm – cytoplasm of muscle – Sarcoplasm – cytoplasm of muscle – has most mitochondria of any cellhas most mitochondria of any cell

Sarcoplasmic Reticulum – specialized Sarcoplasmic Reticulum – specialized SER for storing and releasing and SER for storing and releasing and actively transporting Caactively transporting Ca++++

Muscle Cell Anatomy Cont.Muscle Cell Anatomy Cont.Transverse Tubules – special Transverse Tubules – special passages for Na+ that pass over SRpassages for Na+ that pass over SRMyofibrils – cylindrical organelles that Myofibrils – cylindrical organelles that contain the myofilaments needed for contain the myofilaments needed for muscle contractionmuscle contractionMyofilaments – protein fibersMyofilaments – protein fibers

Thick filaments – myosinThick filaments – myosinThin filaments – actinThin filaments – actinSarcomere – functional unit of Sarcomere – functional unit of contraction – part of a myofibrilcontraction – part of a myofibril

Sarcomere AnatomySarcomere AnatomyZ Line – membrane that marks the end of Z Line – membrane that marks the end of the sarcomere – actin is attached herethe sarcomere – actin is attached hereA Band – Dark part of sarcomere – contain A Band – Dark part of sarcomere – contain myosin (some parts have overlapping myosin (some parts have overlapping actin)actin)H zone – very center of A band – a little H zone – very center of A band – a little lighter than rest of A band since only lighter than rest of A band since only contain myosin – no overlapping actincontain myosin – no overlapping actinM line – membrane in the center of the M line – membrane in the center of the sarcomeresarcomereI band – at edges of sarcomere – light I band – at edges of sarcomere – light band – contains only actinband – contains only actinI band disappears during contraction and I band disappears during contraction and so does the H zone as actin is pulled in so does the H zone as actin is pulled in over myosinover myosin

Muscle AnatomyMuscle Anatomy

FiberFiber – cell – cell

EndomysiumEndomysium – fibrous sheath around – fibrous sheath around each muscle cell or fibereach muscle cell or fiber

FasicleFasicle – bundle of muscle cells surround – bundle of muscle cells surround by the by the perimysiumperimysium fibrous sheath fibrous sheath

Muscle – bundle of fasicles covered in the Muscle – bundle of fasicles covered in the epimysiumepimysium

TendonTendon – fibrous proteins attaching the – fibrous proteins attaching the muscle to the bonemuscle to the bone

MUSCLE INNERVATIONMUSCLE INNERVATIONMotor Unit – One nerve and all of the Motor Unit – One nerve and all of the muscle cells or fibers that it innervatesmuscle cells or fibers that it innervates

All of None Principle – when you contract a All of None Principle – when you contract a motor unit, ever fiber or cell in the motor motor unit, ever fiber or cell in the motor unit contracts and each contracts to the unit contracts and each contracts to the fullest extentfullest extent

How can you get different strengths of How can you get different strengths of contraction in the same muscle???contraction in the same muscle???

# OF MOTOR UNIT ACTIVATE!# OF MOTOR UNIT ACTIVATE!

Neuromuscular JunctionNeuromuscular Junction

Sarcolemma – cell membraneSarcolemma – cell membraneMotor end plate – specialized part of Motor end plate – specialized part of sarcolemma with neurotransmitter sarcolemma with neurotransmitter receptors – part where muscle membrane receptors – part where muscle membrane meets the nervemeets the nerveAxon – cytoplasmic extension of the nerve Axon – cytoplasmic extension of the nerve cell that meets the musclecell that meets the muscleAcetylcholine (Ach) – neurotransmitter Acetylcholine (Ach) – neurotransmitter that sets off contractionthat sets off contractionSynaptic Cleft – space in between axon Synaptic Cleft – space in between axon and motor end plate where Ach is dumpedand motor end plate where Ach is dumpedT-Tubule – when Ach binds to receptors on T-Tubule – when Ach binds to receptors on motor end plate – opens T-tubule channels motor end plate – opens T-tubule channels and allows Na+ to flow inand allows Na+ to flow in

Components of Muscle ContractionComponents of Muscle Contraction

Myosin – thick filament that pulls actin in Myosin – thick filament that pulls actin in to cause contractionto cause contractionActin – thin filament/has binding sites for Actin – thin filament/has binding sites for myosinmyosinTropomyosin – a rope like protein that Tropomyosin – a rope like protein that wraps around actin covering the active wraps around actin covering the active sites on actin so that myosin can’t bind to sites on actin so that myosin can’t bind to the actinthe actinTroponin – small proteins that attach to Troponin – small proteins that attach to the tropomyosin– has a Ca++ binding site the tropomyosin– has a Ca++ binding site – when Ca++ binds it changes shape and – when Ca++ binds it changes shape and in turn causes the tropomyosin to swivel in turn causes the tropomyosin to swivel off of the active sites on actinoff of the active sites on actin

ContractionContraction

Ach is released from the axon into Ach is released from the axon into the synaptic cleftthe synaptic cleft

Ach binds to receptors on the motor Ach binds to receptors on the motor end plateend plate

This opens the T tubules – Na+ flow This opens the T tubules – Na+ flow in through the T-tubulesin through the T-tubules

Steps of ContractionSteps of ContractionNa+ flowing in through the T-tubules Na+ flowing in through the T-tubules causes channels in SR to open causes channels in SR to open releasing Ca++releasing Ca++Ca++ attaches to troponin causing it Ca++ attaches to troponin causing it to change shapeto change shapeThe troponin shape change causes The troponin shape change causes the tropomyosin to swivel off of the the tropomyosin to swivel off of the actin active sitesactin active sitesActivated myosin heads pop up and Activated myosin heads pop up and grab on to actin and swivel forward grab on to actin and swivel forward (power stroke) dragging the actin (power stroke) dragging the actin inwardinward

ContractionContraction

Many myosin heads are popping up Many myosin heads are popping up and grabbing on all at once – they and grabbing on all at once – they are staggered so that some are are staggered so that some are always attachedalways attached

This continues as long as there is This continues as long as there is Calcium present and ATP to power Calcium present and ATP to power the process (usually don’t run out of the process (usually don’t run out of the ATP)the ATP)

How to Stop a Normal ContractionHow to Stop a Normal Contraction

This is not exhaustion – just normal This is not exhaustion – just normal stoppingstopping

Destroy the AchDestroy the Ach

Pump out the Na+Pump out the Na+

Pump all of the Ca++ back into the Pump all of the Ca++ back into the SRSR

Motions Muscles MakeMotions Muscles MakeFlexion – decreasing angle in the Flexion – decreasing angle in the joint – bringing bones closer togetherjoint – bringing bones closer together

Extension – increasing the angle in Extension – increasing the angle in the joint – straightening the jointthe joint – straightening the joint

Hyperextension – straightening more Hyperextension – straightening more than 180than 18000

Abduction – movement of a limb Abduction – movement of a limb away from the midline of the bodyaway from the midline of the body

Adduction – movement of a limb Adduction – movement of a limb toward the midlinetoward the midline

Motions ContinuedMotions Continued

Rotation – movement of a bone Rotation – movement of a bone around its axis without medial or around its axis without medial or lateral displacementlateral displacementCircumduction – movement of distal Circumduction – movement of distal portion around stationary proximal portion around stationary proximal portion of the boneportion of the bonePronation – turning the palms down Pronation – turning the palms down (special kind of rotation)(special kind of rotation)Supination – turning the palms upSupination – turning the palms up

(also rotation)(also rotation)

Motions ContinuedMotions Continued

Inversion – turning the sole of the Inversion – turning the sole of the foot infoot in

Eversion – turning the sole of the foot Eversion – turning the sole of the foot outout

Dorsiflexion – pulling the toes up Dorsiflexion – pulling the toes up toward the tibia toward the tibia

Plantar Flexion – pointing toes – Plantar Flexion – pointing toes – pushing them downwardpushing them downward

Muscle TwitchMuscle TwitchA single muscle contractionA single muscle contraction

Latent period – Ach is released, Na+ Latent period – Ach is released, Na+ rushes in, Ca++ is released, active sites rushes in, Ca++ is released, active sites are uncovered on actin, myosin binds to are uncovered on actin, myosin binds to actinactinContraction period – myosin is pulling actin Contraction period – myosin is pulling actin inwardinwardRelaxation period – Ca++ is being sucked Relaxation period – Ca++ is being sucked up by the SR, tropomyosin is recovering up by the SR, tropomyosin is recovering active sites on actin, myosin can no longer active sites on actin, myosin can no longer bind to actin, Na+ is also pumped out and bind to actin, Na+ is also pumped out and Ach is destroyed in the synaptic cleftAch is destroyed in the synaptic cleft

Energy UsageEnergy Usage

Creatine phosphate – enzyme Creatine phosphate – enzyme transfers phosphate from creatine to transfers phosphate from creatine to ADP – make ATP quickly for a few ADP – make ATP quickly for a few secondssecondsGlycolysis/Fermentation – only make Glycolysis/Fermentation – only make 2 ATP/glucose – ineffective but don’t 2 ATP/glucose – ineffective but don’t need oxygenneed oxygenAerobic Cellular Respiration – make Aerobic Cellular Respiration – make 38 ATP/glucose – only efficient way 38 ATP/glucose – only efficient way to make enough ATP for sustained to make enough ATP for sustained muscle contractionmuscle contraction

Aerobic RespirationAerobic RespirationNeeds a lot of oxygen to burn glucose this Needs a lot of oxygen to burn glucose this way and make ATPway and make ATPMyoglobin – red protein in muscle that Myoglobin – red protein in muscle that binds oxygen and stores itbinds oxygen and stores itWhy need oxygen?Why need oxygen?– Make ATP aerobicallyMake ATP aerobically– Replenish creatine phosphateReplenish creatine phosphate– Reload myoglobinReload myoglobin

Oxygen debt – can’t get enough , can’t Oxygen debt – can’t get enough , can’t make enough ATP – feel fatigued, make enough ATP – feel fatigued, breathe heavilybreathe heavily

Fast vs. Slow Twitch MusclesFast vs. Slow Twitch MusclesFast Twitch MusclesFast Twitch Muscles– Contract fasterContract faster– White/Little myoglobinWhite/Little myoglobin– Bigger SR/Faster Ca++ releaseBigger SR/Faster Ca++ release

Slow Twitch MusclesSlow Twitch Muscles– Take longer to contract but can sustain Take longer to contract but can sustain

the contractionthe contraction– Red/Lots of myoglobinRed/Lots of myoglobin– More mitochondriaMore mitochondria

Isotonic Muscle Contractions – muscle shortens – Isotonic Muscle Contractions – muscle shortens – force of muscle is greater than the loadforce of muscle is greater than the loadIsometric – muscle doesn’t shorten – force of load Isometric – muscle doesn’t shorten – force of load > force of muscle> force of muscleMuscle Tone – some motor units are contracted Muscle Tone – some motor units are contracted but not enough to move the musclebut not enough to move the muscleHypertrophy – muscle cells increase in size by Hypertrophy – muscle cells increase in size by increasing the amount of actin and myosin, SR, increasing the amount of actin and myosin, SR, and mitochondria due to stress on muscleand mitochondria due to stress on muscleAtrophy – shrinkage of a muscle because each Atrophy – shrinkage of a muscle because each muscle cell gets smaller – loses actin and myosin muscle cell gets smaller – loses actin and myosin due to disusedue to disuseRigor Mortis – after death, calcium leaks out of SR Rigor Mortis – after death, calcium leaks out of SR and the troponin/tropomyosin complex is moved and the troponin/tropomyosin complex is moved from actin active sites – myosin binds but not ATP from actin active sites – myosin binds but not ATP is being produced to unattach it so muscle is being produced to unattach it so muscle becomes rigid – as tissue starts to break down becomes rigid – as tissue starts to break down after a day, it goes awayafter a day, it goes away

Cardiac MuscleCardiac MuscleNo neurons innervating cells, no motor units – No neurons innervating cells, no motor units – one pacemaker and then conductive protein one pacemaker and then conductive protein fibers to carry the impulse to other cardiac cellsfibers to carry the impulse to other cardiac cellsGap junctions (intercalated discs) cause ions to Gap junctions (intercalated discs) cause ions to flow from cell to cell to get a coordinated flow from cell to cell to get a coordinated contractioncontractionImpulse starts in atria and then travels through Impulse starts in atria and then travels through ventricles so atria contract and then ventriclesventricles so atria contract and then ventriclesThe cardiac muscle cells have the same The cardiac muscle cells have the same arrangement of actin and myosin (striations) but arrangement of actin and myosin (striations) but only have one nucleus and have bigger only have one nucleus and have bigger mitochondria and only 1 T-Tubulemitochondria and only 1 T-TubuleContracts slower – takes more time for calcium to Contracts slower – takes more time for calcium to diffusediffuseContracts about 70 times/min.Contracts about 70 times/min.Long Refractory period so there is no tetanus Long Refractory period so there is no tetanus even when the hear is beating fasteven when the hear is beating fast

Smooth MuscleSmooth Muscle

Contracts slower and longer (takes longer Contracts slower and longer (takes longer for Ca++ to diffuse and to be pumped for Ca++ to diffuse and to be pumped back into the SR)back into the SR)Actin and myosin different from cardiac Actin and myosin different from cardiac and skeletal – actin is attached to dense and skeletal – actin is attached to dense bodies and membrane but myosin still bodies and membrane but myosin still pulls it in – just pulls in in every directionpulls it in – just pulls in in every directionNo motor units – instead most are single No motor units – instead most are single unit junctions – a nerve synapses with one unit junctions – a nerve synapses with one smooth muscle cell and the impulse smooth muscle cell and the impulse spreads thru gap junctions so it all spreads thru gap junctions so it all contracts in a wavecontracts in a waveIn pupil – multi-unit – each smooth muscle In pupil – multi-unit – each smooth muscle cell has its own nervecell has its own nerve