3 types:3 types:

1) 1) skeletalskeletal-pulls on bones to -pulls on bones to cause movementcause movement

2) 2) cardiaccardiac-pumps blood thru -pumps blood thru circulatory systemcirculatory system

3) 3) smoothsmooth-pushes fluids & -pushes fluids & solids thru body, regulates solids thru body, regulates blood vessel diameterblood vessel diameter

Skeletal Muscle:Skeletal Muscle:

Functions:Functions:

a) Produce skeletal a) Produce skeletal movementsmovements

-contract & tendons pull -contract & tendons pull on boneson bones

b) Maintain posture & b) Maintain posture & positionposition-constant tension keeps -constant tension keeps head in position & head in position & body over feetbody over feet

c) Soft tissue supportc) Soft tissue support-muscles lining abdomino- -muscles lining abdomino-

pelvic cavity support pelvic cavity support weight of organs & weight of organs &

offer offer protectionprotection

d) Guard entrances & exitsd) Guard entrances & exits-closes openings in -closes openings in

digestive & urinary digestive & urinary tractstracts

e) Produce heate) Produce heat-contractions require -contractions require

energy that is energy that is converted into heat to converted into heat to maintain temp.maintain temp.

f) Nutrient reserve storagef) Nutrient reserve storage

-proteins in muscles are -proteins in muscles are broken down to broken down to provide amino acids provide amino acids for enzymes & for enzymes &

energyenergy

OrganizationOrganization

-3 connective tissue layers-3 connective tissue layers

1) 1) Epimysium:Epimysium:

-surrounds entire -surrounds entire musclemuscle

-separates muscle -separates muscle from other from other tissues/organstissues/organs

2) 2) Perimysium:Perimysium:-divides muscle into -divides muscle into

compartmentscompartments-each contains a -each contains a

fasciclefascicle-- bundle of bundle of muscle muscle fibersfibers

-each receives a branch -each receives a branch of blood vessels & of blood vessels & nervesnerves

3) 3) Endomysium:Endomysium:

-surrounds individual -surrounds individual muscle fibers (cells)muscle fibers (cells)

Collagen fibers from each Collagen fibers from each layer join to form a layer join to form a

tendontendon (connects muscle (connects muscle to to bone) or bone) or aponeurosisaponeurosis

(broad sheet that (broad sheet that connects muscle to connects muscle to

bone)bone)

Microscopic structureMicroscopic structure

-cells can be 30 cm long & -cells can be 30 cm long & 100 100 µm (.1 mm)diameterµm (.1 mm)diameter

-very large compared to -very large compared to most most cellscells

-multinucleate-multinucleate

-may be 100’s/cell-may be 100’s/cell

-lie just below membrane-lie just below membrane

--Sarcolemma-Sarcolemma-plasma plasma membrane of muscle membrane of muscle

fiberfiber

--SarcoplasmSarcoplasm-cytoplasm-cytoplasm

--Transverse (T) tubules-Transverse (T) tubules- narrow tubes, continuous narrow tubes, continuous w/ sarcolemma that w/ sarcolemma that extend thru sarcoplasmextend thru sarcoplasm

-fluid-filled-fluid-filled-contain same electrical -contain same electrical charge as sarcolemmacharge as sarcolemma-send impulse to entire -send impulse to entire

fiber so it all contract fiber so it all contract togethertogether

--Myofibrils-Myofibrils- cylindrical structures cylindrical structures that run the length of a fiberthat run the length of a fiber

-made of -made of myofilaments:myofilaments: thin thin strands/filaments of strands/filaments of proteinprotein

-2 types-2 types

1)1)Thin filamentsThin filaments-actin-actin

2)2)Thick filamentsThick filaments--myosinmyosin

-can shorten & are -can shorten & are responsible for muscle responsible for muscle contractingcontracting

-anchored to ends of -anchored to ends of sarcolemma which sarcolemma which eventually becomes a eventually becomes a tendon which pulls on tendon which pulls on bonebone-space filled w/ mitochondria & -space filled w/ mitochondria &

glycogenglycogen

--Sarcoplasmic reticulum-Sarcoplasmic reticulum- membrane complexs, similar membrane complexs, similar to smooth ERto smooth ER

-surround each myofibril -surround each myofibril between T-tubulesbetween T-tubules

--terminal cisternaeterminal cisternae--expanded, fused expanded, fused chambers where SR chambers where SR meets T-tubulemeets T-tubule

--triadtriad-2 terminal cisternae & -2 terminal cisternae & a a T-tubuleT-tubule

-cells pump CA-cells pump CA2+2+ ions out of ions out of cells, they also transport cells, they also transport them into the terminal them into the terminal cisternaecisternae-may have 1000x higher -may have 1000x higher

concentration of free concentration of free CaCa2+2+

-calsequestrin (protein) -calsequestrin (protein) binds Cabinds Ca2+2+

-total Ca-total Ca2+2+ may be may be 40,000x greater40,000x greater

-contractions begin when -contractions begin when CaCa2+2+ ions are ions are

released released into into sarcoplasmsarcoplasm

--Sarcomere-Sarcomere- repeating, repeating, individual contractile units in individual contractile units in myofibrilsmyofibrils

-1 myofibril can have 10,000-1 myofibril can have 10,000

-4 components:-4 components:

1) Thick filaments-myosin 1) Thick filaments-myosin w/ associated w/ associated titintitin (elastic filaments)(elastic filaments)

2) Think filaments-actin2) Think filaments-actin

3) Stabilizing proteins3) Stabilizing proteins

4) Regulating proteins4) Regulating proteins

-create banded/striated -create banded/striated appearanceappearance

I-band-I-band-light band (only actin)light band (only actin)A-band-A-band-dark (myosin & actin)dark (myosin & actin)H-zone-H-zone- only myosin only myosin

M-lineM-line-proteins that stabilize -proteins that stabilize position of thick bandsposition of thick bands

Zone of overlapZone of overlap-thin filaments -thin filaments between thick between thick

-6 thin surround a thick-6 thin surround a thick

-3 thick surround a thin-3 thick surround a thin

p. 289p. 289

Z-lineZ-line-boundary between -boundary between sarcomeressarcomeres

-proteins that connect thin -proteins that connect thin filamentsfilaments

-titin proteins extend from -titin proteins extend from thick filaments & attach thick filaments & attach

to to Z-lineZ-line

-helps filament alignment-helps filament alignment

-Surrounded by 2 T-tubules & -Surrounded by 2 T-tubules & triads located at zones of triads located at zones of overlapoverlap

-Thin filaments:-Thin filaments:

-each contains 4 proteins-each contains 4 proteins

--active siteactive site: area where : area where myosin can bindmyosin can bind

-covered by troponin- -covered by troponin- tropomyosin complex tropomyosin complex when a muscle is when a muscle is relaxedrelaxed

-in resting muscle, -in resting muscle, intracellular Caintracellular Ca2+2+

concentrations are very concentrations are very low & binding site is low & binding site is emptyempty

-Troponin-tropomyosin -Troponin-tropomyosin complex must move in complex must move in order for contraction to order for contraction to occuroccur-calcium triggers process-calcium triggers process

-Thick filaments-Thick filaments

-contain 300 twisted myosin -contain 300 twisted myosin moleculesmolecules

--tailtail-where molecules are -where molecules are bound to each otherbound to each other

--headhead-projects toward actin-projects toward actin

-made of 2 globular -made of 2 globular protein subunitsprotein subunits

-interact w/ active site to -interact w/ active site to form cross-bridgesform cross-bridges

-hinge that allows head -hinge that allows head to to pivot freelypivot freely

-arranged so tails point -arranged so tails point toward M-linetoward M-line

-core contains titin that -core contains titin that extends past fiber & extends past fiber & attaches to Z-lineattaches to Z-line

ContractionContraction

Events:Events:

1)H-zones & I-bands get 1)H-zones & I-bands get smallersmaller

2)Zones of Overlap get larger2)Zones of Overlap get larger

3)Z-lines get closer together3)Z-lines get closer together

4)A-band width stays 4)A-band width stays constantconstant

Sliding Filament TheorySliding Filament Theory-thin -thin filaments slide toward M-line filaments slide toward M-line moving across thick moving across thick filaments, causing sarcomere filaments, causing sarcomere to shorten & muscles to to shorten & muscles to contractcontract

-When muscles contract they -When muscles contract they put put tensiontension on attached on attached tendonstendons

Control of Muscle ActivityControl of Muscle Activity-nerves from central nervous -nerves from central nervous system (brain & spinal cord) system (brain & spinal cord) control contractionscontrol contractions--Neuromuscular junctionNeuromuscular junction: area : area

where nerve connects/ where nerve connects/ communicates w/ muscle communicates w/ muscle fiberfiber

-1/fiber-1/fiber

-ends w/ -ends w/ synaptic terminalsynaptic terminal-filled with -filled with acetylcholineacetylcholine

(Ach)-a (Ach)-a neurotransmitter that neurotransmitter that is released by the is released by the neuron from the neuron from the synaptic terminal, synaptic terminal, attaches to muscle attaches to muscle fiber & alters the fiber & alters the permeability of the permeability of the sarcolemmasarcolemma

--Synaptic cleftSynaptic cleft: space : space between synaptic terminal between synaptic terminal

& & muscle sarcolemmamuscle sarcolemma

--Motor end plateMotor end plate: sarcolemma : sarcolemma opposite synaptic terminal opposite synaptic terminal that houses receptors that houses receptors where Ach bindswhere Ach binds

-folded to -folded to surface area surface area

--AcetylcholinesteraseAcetylcholinesterase: : (AChE)-enzymes that (AChE)-enzymes that breaks down ACh, found breaks down ACh, found in synaptic cleft & in synaptic cleft & sarcolemmasarcolemma

-Steps of Stimulation-Steps of Stimulation

1) 1) Action potentialAction potential: : (electrical (electrical impulse to impulse to signal release signal release of ACh) of ACh) reaches synaptic reaches synaptic terminal terminal

2) ACh is released thru 2) ACh is released thru exocytosis into synaptic exocytosis into synaptic cleftcleft

3) ACh binds to motor end 3) ACh binds to motor end plate receptors & plate receptors &

changes changes permeability to permeability to NaNa++ ions, ions, which move into which move into

sarcoplasm until sarcoplasm until AChE AChE removes ACh removes ACh from from receptor sitesreceptor sites

4) Na4) Na++ movement creates movement creates an an action potential in action potential in

sarcolemma, moves sarcolemma, moves inward thru T-tubulesinward thru T-tubules

5) ACh broken down by 5) ACh broken down by AChE & system is ready AChE & system is ready for another action for another action potentialpotential

Excitation-Contraction Coupling:Excitation-Contraction Coupling: process that uses the stimulus process that uses the stimulus from an action potential to from an action potential to create a muscle contractioncreate a muscle contraction

-occurs at triads-occurs at triads

-action potential causes -action potential causes cisternae to release Cacisternae to release Ca2+2+ ions ions into sarcoplasm at a into sarcoplasm at a sarcomere’s zone of overlapsarcomere’s zone of overlap

-normally troponin (enzyme) -normally troponin (enzyme) covers the active site of actin covers the active site of actin strands, Castrands, Ca2+2+ causes causes troponin troponin to release & allow to release & allow for myosin for myosin heads to bondheads to bond

-begins the contraction -begins the contraction cyclecycle

Contraction cycle:Contraction cycle:

1) Troponin removed & active 1) Troponin removed & active sites availablesites available

2) Myosin head binds to active 2) Myosin head binds to active site forming a cross-bridge site forming a cross-bridge (requires 1 ATP)(requires 1 ATP)

3) Myosin heads pivot from 3) Myosin heads pivot from being pointed away from the being pointed away from the M-line to being pointed M-line to being pointed towards towards it (it (power strokepower stroke))

4) Cross-bridges detach 4) Cross-bridges detach (myosin head lets go of (myosin head lets go of active site)active site)

5) Another ATP is split to re-5) Another ATP is split to re-energize free myosin head energize free myosin head which causes it to pivot back which causes it to pivot back to its original positionto its original position

-Cycle begins again as long as -Cycle begins again as long as CaCa2+2+ is present & ATP is is present & ATP is

availableavailable-Each power stroke shortens -Each power stroke shortens the sarcomere by 1%the sarcomere by 1%

-Length of contraction depends -Length of contraction depends on:on:

1) Length of stimulation at 1) Length of stimulation at neuromuscular junctionneuromuscular junction

2) Availability of free Ca2) Availability of free Ca2+2+ ions in sarcoplasmions in sarcoplasm

3) Availability of ATP3) Availability of ATP

-ACh binding occurs only -ACh binding occurs only briefly, so action potentials briefly, so action potentials must continue to be applied must continue to be applied in rapid succession to in rapid succession to maintain a contractionmaintain a contraction-Once action potential ends, -Once action potential ends, sarcoplasmic reticulum sarcoplasmic reticulum permeability changes & permeability changes & absorbs Caabsorbs Ca2+2+, active site is , active site is recoveredrecovered

-sarcomere slowly returns to -sarcomere slowly returns to original lengthoriginal length

-at death, no more nutrients/ -at death, no more nutrients/ oxygen cycles, Caoxygen cycles, Ca2+2+ enters enters sarcoplasm which triggers sarcoplasm which triggers contraction. Cross-bridges contraction. Cross-bridges can’t detach because there’s can’t detach because there’s no no ATP-causes ATP-causes rigor mortisrigor mortis--constant contraction of skeletal constant contraction of skeletal

muscles at death, lasts 15-25 muscles at death, lasts 15-25 hours until autolytic enzymes hours until autolytic enzymes break down Z-lines & titinbreak down Z-lines & titin

Tension:Tension:-amount of tension depends on -amount of tension depends on

number of pivoting cross-number of pivoting cross-bridgesbridges-level at muscle fibers depends -level at muscle fibers depends

on:on:a) resting length & size of a) resting length & size of

zone of overlapzone of overlapb) frequency of stimulationb) frequency of stimulation

-sarcomere length must be -sarcomere length must be optimal for good tensionoptimal for good tension

-allows for max. # of cross--allows for max. # of cross-bridges to form & pull on bridges to form & pull on

fibersfibers-extreme stretching/ -extreme stretching/

compression is prevented compression is prevented by muscle arrangement, by muscle arrangement, connective tissue, & bonesconnective tissue, & bones

-titin fibers also help prevent -titin fibers also help prevent extreme stretchingextreme stretching

-stimulation frequency-stimulation frequency

-single contraction lasts 7--single contraction lasts 7-100 milliseconds100 milliseconds

-this can be extended by -this can be extended by repeated stimulation repeated stimulation

& & sustained sustained contractions contractions which which tensiontension

--TwitchTwitch: single stimulus-: single stimulus-contraction-relaxation contraction-relaxation sequence in a muscle fibersequence in a muscle fiber

-time varies-time varies

-3 phases-3 phases

1) 1) Latent periodLatent period: action : action potential releases ACh & potential releases ACh & SR releases CaSR releases Ca2+2+

-no tension produced (2 -no tension produced (2 msec)msec)

2) 2) Contraction phase:Contraction phase: tension tension rises to a peak, rises to a peak, CaCa2+2+ binds to troponin, binds to troponin, active active sites exposed, cross-sites exposed, cross-

bridges form (2-15 bridges form (2-15 msec)msec)

3) 3) Relaxation phase:Relaxation phase: Ca Ca2+2+ levels fall, active sites levels fall, active sites covered w/ tropomyosin covered w/ tropomyosin

& & cross-bridges decrease, cross-bridges decrease, tension falls (15-40 tension falls (15-40

msec)msec)

http://www.cardiovascularultrasound.com/content/3/1/27/figure/F6?highres=y

--Treppe:Treppe: second stimulation is second stimulation is applied immediately after applied immediately after

relaxation period ends, relaxation period ends, tension tension increases w/ each increases w/ each stimulus stimulus until max. tension is until max. tension is reached reached (after 30-50 (after 30-50 stimulations)stimulations)

-results from gradual -results from gradual in in CaCa2+2+ because SR can’t because SR can’t reabsorb allreabsorb all

--Wave summation:Wave summation: second second stimulus begins before stimulus begins before relaxation phase endsrelaxation phase ends

-create more powerful -create more powerful contractionscontractions

-tension will rise to 4x treppe -tension will rise to 4x treppe max.max.-rapid cycles that maintain -rapid cycles that maintain

max. max. level during wave level during wave summation-summation-incompleteincompletetetanustetanus

--Complete tetanus:Complete tetanus: faster faster stimulations eliminates stimulations eliminates relaxation phaserelaxation phase

-SR can’t reabsorb Ca-SR can’t reabsorb Ca2+2+

-creates continuous, -creates continuous, strong contractionstrong contraction

Tension in Whole MuscleTension in Whole Muscle

-dependent on tension in fibers -dependent on tension in fibers & # of fibers contracting& # of fibers contracting

-twitch is ineffective for useful -twitch is ineffective for useful movement, treppe, or tetanus movement, treppe, or tetanus is usedis used

--Motor unit:Motor unit: all muscle fibers all muscle fibers controlled by a single motor controlled by a single motor neuronneuron

-fine motor areas have less -fine motor areas have less fibers/neuron than gross fibers/neuron than gross motormotor

-smallest motor units are -smallest motor units are activated first during a activated first during a contraction, larger units contraction, larger units create faster more create faster more powerful movementpowerful movement

--recruitment:recruitment: increasing # of increasing # of motor units contracting motor units contracting based on movementbased on movement

-all motor units contracting in -all motor units contracting in complete tetanus creates complete tetanus creates peak tension can’t be peak tension can’t be sustained because ATP sustained because ATP reserves run outreserves run out

-units usually take turns -units usually take turns contracting so some have contracting so some have time to recovertime to recover-asynchronous motor unit -asynchronous motor unit

summationsummation

--Muscle tone:Muscle tone: resting tension in resting tension in skeletal musclesskeletal muscles

-don’t cause motion-don’t cause motion

-little tone=limp/flaccid -little tone=limp/flaccid musclemuscle

-motor units take turns -motor units take turns contractingcontracting

-stabilizes & maintains body -stabilizes & maintains body position, prevents position, prevents

sudden sudden motions, & allows motions, & allows muscles to absorb muscles to absorb

sudden sudden shockshock

Contraction classificationsContraction classifications1) 1) Isotonic contraction:Isotonic contraction: tension tension rises & length of muscle rises & length of muscle changeschanges

2 types:2 types:a) a) Concentric contractions:Concentric contractions:

muscle tension exceeds muscle tension exceeds resistance & muscle resistance & muscle shortensshortens-e.g. flexion of elbow-e.g. flexion of elbow

b) b) Eccentric contraction:Eccentric contraction: peak peak tension is less than tension is less than load & load & muscle elongates muscle elongates due to due to pull of another pull of another muscle or muscle or gravitygravity

-e.g. controlled -e.g. controlled extension extension of elbowof elbow

2) 2) Isometric contractionIsometric contraction: : contraction where muscle contraction where muscle doesn’t change length doesn’t change length because tension never because tension never exceeds resistanceexceeds resistance

-fibers shorten, but -fibers shorten, but connective tissue connective tissue stretchesstretches

-after contraction, fibers return -after contraction, fibers return to original length because of to original length because of elastic forces, opposing elastic forces, opposing

muscle contractions, & muscle contractions, & gravitygravity

Fiber Types:Fiber Types:

1. 1. Fast Fibers:Fast Fibers: large fibers that contract large fibers that contract quickly & forcefullyquickly & forcefully

-fatigue rapidly-fatigue rapidly

-”white meat”-”white meat”

2. 2. Slow FibersSlow Fibers: smaller fibers that take : smaller fibers that take longer to reach peak tensionlonger to reach peak tension

-more blood & myoglobin-more blood & myoglobin

-difficult to fatigue -difficult to fatigue

-”red/dark meat”-”red/dark meat”

Organization of the muscular Organization of the muscular systemsystem

-muscle fibers in fascicle are -muscle fibers in fascicle are parallel, but fascicle parallel, but fascicle organization variesorganization varies

TypesTypes

1. 1. Parallel musclesParallel muscles: fascicles : fascicles parallel to long axisparallel to long axis

-includes most skeletal muscles-includes most skeletal muscles

-e.g. sartorius-e.g. sartorius

-spindle-shaped w/ central -spindle-shaped w/ central body (belly) are called body (belly) are called fusiform fusiform (e.g. biceps brachii)(e.g. biceps brachii)

2. 2. Convergent muscleConvergent muscle: fascicles : fascicles extend over a broad area & extend over a broad area & converge at a common converge at a common

attachment siteattachment site

-shaped like fan or triangle w/ -shaped like fan or triangle w/ tendon at apextendon at apex

-e.g. pectoralis & trapezius-e.g. pectoralis & trapezius

3. 3. Pennate musclePennate muscle: fascicles : fascicles form form a common angle w/ the a common angle w/ the tendontendon

a. unipennate-muscle fibers on a. unipennate-muscle fibers on same side of tendonsame side of tendon

b. bipennate-fibers on both b. bipennate-fibers on both sides sides of tendonof tendon

c. multipennate-tendon c. multipennate-tendon branches branches w/in pennatew/in pennate

-e.g. deltoid-e.g. deltoid

4. 4. Circular muscle/sphincterCircular muscle/sphincter: : fascicles are concentrically fascicles are concentrically arranged around openingarranged around opening

-contraction decreases -contraction decreases diameterdiameter

-e.g. orbicular oris-e.g. orbicular oris

LeversLevers: rigid structure that : rigid structure that moves on a fixed point moves on a fixed point ((fulcrumfulcrum))

-moves when an applied force -moves when an applied force (AF) can overcome a (AF) can overcome a

resistance (R)resistance (R)

-bone is lever, joint is fulcrum, -bone is lever, joint is fulcrum, & muscle is AF& muscle is AF

-can change-can change

a. direction of applied forcea. direction of applied force

b. distance/speed of b. distance/speed of movement produced by movement produced by AFAF

c. effective strength of AFc. effective strength of AF

Classes of LeversClasses of Levers

1. 1. 11stst class class: seesaw: seesaw

-few in body-few in body

-e.g.-extension -e.g.-extension

of neckof neck

2. 2. 22ndnd class class: :

-small force can move -small force can move

a larger weighta larger weight

-e.g. ankle extension -e.g. ankle extension (plantarflexion)(plantarflexion)

3. 3. 33rdrd class class::

-most common in -most common in

bodybody

-speed/distance -speed/distance ↑ ↑

at expense of at expense of

effective forceeffective force

TerminologyTerminologyOriginOrigin: place where fixed end of muscle : place where fixed end of muscle

attachesattachesInsertionInsertion: site where movable end : site where movable end

attaches to another structureattaches to another structureActionAction: specific movement produced : specific movement produced

when a muscle contractswhen a muscle contracts-based on movement from -based on movement from anatomical positionanatomical position-muscles work in groups for complex -muscles work in groups for complex

motionsmotions

AgonistAgonist: (prime mover) muscles : (prime mover) muscles that’s contracting to create a that’s contracting to create a particular movementparticular movement

AntagonistAntagonist: muscle whose action : muscle whose action opposes the motion of the opposes the motion of the agonistagonist

e.g. biceps brachii vs. triceps e.g. biceps brachii vs. triceps brachii – functional oppositesbrachii – functional opposites

SynergistSynergist: helps agonist work : helps agonist work more efficiently, provide more more efficiently, provide more pull, stabilize originpull, stabilize origin

--fixatorsfixators: synergists that : synergists that stabilize origin by preventing stabilize origin by preventing movement in other jointsmovement in other joints

NamingNaming

1. Location – Temporalis1. Location – Temporalis

2. Origin/Insertion – (12. Origin/Insertion – (1stst/2/2ndnd) – ) – SternocleidomastoidSternocleidomastoid

3. Fascicle organization3. Fascicle organization

-Rectus (straight)-Rectus -Rectus (straight)-Rectus abdominisabdominis

-Oblique/Transversus-Oblique/Transversus

4. Relative position4. Relative position-Superficialis/Externus-Superficialis/Externus-Internus/Profundus-Internus/Profundus

5. Structure5. Structure-Biceps (2 heads), Triceps (3 -Biceps (2 heads), Triceps (3 heads)heads)-Trapezius (triangle)-Trapezius (triangle)-Longus, Brevis, Maximus, -Longus, Brevis, Maximus, Minimus, Major, MinorMinimus, Major, Minor

6. Action6. Action

-Flexor, Extensor, Pronator, -Flexor, Extensor, Pronator, Abductor, etc.Abductor, etc.