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Exercise 14. Microscopic Anatomy, Organization, and Classification of Skeletal Muscle. SKELETAL MUSCLE. Voluntary or involuntary? Striated or not? Multinucleate or uninucleate?. Terminology. “Myo-” or “-Mys-” = muscle “Sarco-” = flesh. Microscopic Anatomy. - PowerPoint PPT Presentation
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Exercise 14Exercise 14
Microscopic Microscopic Anatomy, Anatomy,
Organization, and Organization, and
Classification of Classification of Skeletal MuscleSkeletal Muscle
SKELETAL MUSCLESKELETAL MUSCLE
Voluntary or involuntary?Voluntary or involuntary? Striated or not?Striated or not? Multinucleate or Multinucleate or
uninucleate?uninucleate?
““Myo-” or “-Mys-” = muscleMyo-” or “-Mys-” = muscle ““Sarco-” = fleshSarco-” = flesh
TerminologyTerminology
Microscopic Microscopic AnatomyAnatomy
Muscle Fiber = Muscle Fiber = long, slender, long, slender, cylindrical, cylindrical, MULTInucleate MULTInucleate cellcell
Nuclei located Nuclei located just under just under sarcolemma (cell sarcolemma (cell membrane)membrane)
Fig. 10-2
Muscle Fiber AnatomyMuscle Fiber Anatomy
SarcolemmaSarcolemma– Plasma membrane of muscle fiberPlasma membrane of muscle fiber– Trans-membrane potential: charge Trans-membrane potential: charge
differences on either sidedifferences on either side SarcoplasmSarcoplasm
– Cytoplasm of muscle fiberCytoplasm of muscle fiber– Stored glycogen, mitochondria, Stored glycogen, mitochondria,
myoglobin, actin, myosinmyoglobin, actin, myosin
Transverse tubulesTransverse tubules– T tubulesT tubules– Narrow tubes, continuous with Narrow tubes, continuous with
sarcolemmasarcolemma– Extend into sarcoplasm, fluid-filledExtend into sarcoplasm, fluid-filled
MyofibrilsMyofibrils– Parallel, extend length of muscle fiberParallel, extend length of muscle fiber– Each muscle fiber contains 100s-1000sEach muscle fiber contains 100s-1000s– Composed of myofilamentsComposed of myofilaments
Actin (thin filaments) & myosin (thick Actin (thin filaments) & myosin (thick filaments)filaments)
Sarcoplasmic Reticulum (SR)Sarcoplasmic Reticulum (SR)– Smooth ERSmooth ER– Tubular network around each myofibrilTubular network around each myofibril– Terminal cisternaeTerminal cisternae: enlarged portion : enlarged portion
of SR on either side of T tubuleof SR on either side of T tubule– Storage/release of CaStorage/release of Ca
Triad = T tubule + 2 terminal Triad = T tubule + 2 terminal cisternaecisternae
Fig. 10-3
Muscle contraction begins when Muscle contraction begins when Calcium ions are released Calcium ions are released – from the terminal cisternaefrom the terminal cisternae– Into the sarcoplasmInto the sarcoplasm
– ADAM cd-romADAM cd-rom
SarcomeresSarcomeres– Organized group of myofilamentsOrganized group of myofilaments– Contractile units, smallest functional Contractile units, smallest functional
unit of muscle fiberunit of muscle fiber– Z-line to Z-lineZ-line to Z-line
Fig. 10-4
SarcomeresSarcomeres
– A band: DARKA band: DARK Thick and Thick and
thin filamentsthin filaments M lineM line is in is in
the middle of the middle of the the sarcomere/A sarcomere/A bandband
– I band: LIGHTI band: LIGHT midline is midline is Z Z
line/discline/disc Thin Thin
filaments filaments onlyonly
Fig. 10-4
MyofilamentsMyofilaments Thick filaments: myosinThick filaments: myosin
– Rod-like tail bound to other myosinRod-like tail bound to other myosin– Head projects outwardHead projects outward
has binding sites for actin (thin filaments), has binding sites for actin (thin filaments), ATPATP
““cross-bridges”cross-bridges”
Fig. 10-7
Contraction: The myosin
head changes
shape & will grab onto the actin…and pull it toward the
M-line
MyofilamentsMyofilaments Thin filaments: 3 types of protein Thin filaments: 3 types of protein
moleculesmolecules– actin actin
Double helix (2 strands) coil around each other Double helix (2 strands) coil around each other has binding sites for myosinhas binding sites for myosin
– Site is blocked by troponin-tropomyosin complex Site is blocked by troponin-tropomyosin complex when muscle’s when muscle’s NOT contractingNOT contracting
– TropomyosinTropomyosin Rod-like, coils around actin to stiffen itRod-like, coils around actin to stiffen it Covers binding sitesCovers binding sites
– TroponinTroponin 3 protein-complex3 protein-complex One of each binds to: actin, tropomyosin, calcium One of each binds to: actin, tropomyosin, calcium
ions (this one’s empty in a resting cell…see ADAM ions (this one’s empty in a resting cell…see ADAM cd)cd)
Connective Tissue Connective Tissue Wrappings:Wrappings:
3 Layers3 Layers
Epimysium = outerEpimysium = outer Perimysium = centralPerimysium = central Endomysium = innerEndomysium = inner
Connective Tissue Connective Tissue WrappingsWrappings
EpimysiumEpimysium– Epi = on (outside layer)Epi = on (outside layer)– Surrounds entire muscleSurrounds entire muscle– Dense layer of collagen fibers, Dense layer of collagen fibers,
connected to connected to deep fasciadeep fascia– Separates muscle from other Separates muscle from other
tissues/organstissues/organs
Fig. 10-1
Connective Tissue Connective Tissue WrappingsWrappings PerimysiumPerimysium
– Peri = around (central layer)Peri = around (central layer)– Divides muscle into compartments:Divides muscle into compartments:
Fascicle = Fascicle = bundlebundle of muscle fibers of muscle fibers (cells)(cells)
– Collagen, elastic fibersCollagen, elastic fibers– Blood vessels, nerves to each Blood vessels, nerves to each
fasciclefascicle Fig. 10-1
Connective Tissue Connective Tissue WrappingsWrappings EndomysiumEndomysium
– Endo = inside (inner layer)Endo = inside (inner layer)– Surrounds individual skeletal Surrounds individual skeletal
muscle cells (fibers)muscle cells (fibers)– Interconnects adjacent muscle Interconnects adjacent muscle
fibersfibers– Capillary networks to supply Capillary networks to supply
blood to cells, nerve fibers to blood to cells, nerve fibers to control musclecontrol muscle
Fig. 10-1
Connective Tissues, cont.Connective Tissues, cont.
Layers are continuous & Layers are continuous & interwoven – blend into one interwoven – blend into one anotheranother
Muscle’s ends: layers unite to Muscle’s ends: layers unite to form form – Bundle: Bundle: TENDONTENDON
Attach skeletal muscles to Attach skeletal muscles to bonesbones Contraction pulls the bone(s)Contraction pulls the bone(s)
– Broad sheet: Broad sheet: APONEUROSISAPONEUROSIS Attach skeletal muscles to Attach skeletal muscles to bones or other bones or other
musclesmuscles
Muscle—covered by epimysiumMuscle—covered by epimysium Fascicles—covered by perimysiumFascicles—covered by perimysium Fiber (cell)—covered by Fiber (cell)—covered by
endomysiumendomysium Myofibril—covered by Myofibril—covered by
sarcoplasmic reticulumsarcoplasmic reticulum Sarcomere—contains thick and Sarcomere—contains thick and
thin filamentsthin filaments
Connective tissue layers!
Blood & Nerve SupplyBlood & Nerve Supply
Muscles need lots of energy, lots of Muscles need lots of energy, lots of oxygenoxygen
Blood vessels supply theseBlood vessels supply these– Each fiber (cell) has capillary blood supplyEach fiber (cell) has capillary blood supply
Contraction stimulated by nerve Contraction stimulated by nerve impulsesimpulses– Axons (nerve fibers) penetrate connective Axons (nerve fibers) penetrate connective
tissue layers, & innervate individual tissue layers, & innervate individual muscle fibers (cells)muscle fibers (cells)
Neuromuscular JunctionNeuromuscular Junction
Junction of motor neuron & a muscle Junction of motor neuron & a muscle fiber fiber – Motor neuron sends a signal to cause a Motor neuron sends a signal to cause a
movement of a skeletal musclemovement of a skeletal muscle
Neuron—elongated portion = axonNeuron—elongated portion = axon– Ends in expanded branches (synaptic Ends in expanded branches (synaptic
terminals) terminals) – synaptic cleft: space between synaptic synaptic cleft: space between synaptic
terminal & muscle fiber’s sarcolemmaterminal & muscle fiber’s sarcolemma
Neuromuscular JunctionNeuromuscular Junction
Synaptic terminalsSynaptic terminals– Contain synaptic vesicles Contain synaptic vesicles
Filled with acetylcholine (ACh)Filled with acetylcholine (ACh)– Neurotransmitter: chemical Neurotransmitter: chemical
released by neuronreleased by neuron
Release of ACh triggers muscle Release of ACh triggers muscle contractioncontraction
Sarcolemma of motor end plate Sarcolemma of motor end plate has has receptorsreceptors to bind ACh to bind ACh
Neuromuscular JunctionNeuromuscular Junction““Motor end plate”Motor end plate”
Sarcolemma highly Sarcolemma highly foldedfolded Increases surface Increases surface
areaarea Sites of ACh Sites of ACh
bindingbinding
Fig. 10-10 “Action Potential”
Neuromuscular JunctionNeuromuscular Junction
Motor unit = A single motor Motor unit = A single motor neuron & ALL the muscle fibers it neuron & ALL the muscle fibers it controlscontrols
Fig. 10-17