exercise 14 microscopic anatomy, organization, and classification of skeletal muscle
TRANSCRIPT
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
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Figure 12.1a Microscopic anatomy of skeletal muscle.
Nuclei Fiber
Dark A band
Light I band
Microscopic Microscopic AnatomyAnatomy
Muscle FiberMuscle Fiber NucleiNuclei
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Figure 12.1b Microscopic anatomy of skeletal muscle.
Myofibril
Mitochondrion
Sarcolemma
NucleusLightI band
DarkA band
Muscle Fiber Anatomy
• Sarcolemma• Sarcoplasm
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Figure 12.1c Microscopic anatomy of skeletal muscle.
Thin (actin) filament
Thick (myosin) filament
Z disc H zone Z disc
M lineI bandA bandI band
• Myofibrils– Composed of myofilaments
• Actin (thin filaments) & myosin (thick filaments)
Transverse tubulesTransverse tubules
Sarcoplasmic Reticulum (SR)Sarcoplasmic Reticulum (SR)– Smooth ERSmooth ER– Terminal cisternaeTerminal cisternae: enlarged portion : enlarged portion
of SR on either side of T tubuleof SR on either side of T tubule
Triad = T tubule + 2 terminal Triad = T tubule + 2 terminal cisternaecisternae
Fig. 10-3
Fig. 10-6
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Figure 12.3 Photomicrograph of muscle fibers, longitudinal and cross sections (800).
Nuclei of muscle fibers
Muscle fibers,longitudinalview
Muscle fibers,cross-sectionalview
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Figure 12.1d Microscopic anatomy of skeletal muscle.
Z discM line
Z disc
Elastic (titin) filaments
Thin (actin) filament
Thick (myosin) filament
• Sarcomeres– Organized group of myofilaments– Contractile units, smallest functional
unit of muscle fiber– Z-line to Z-line
A band: DARK• Thick and
thin• M line in
middle
I band: LIGHT• midline is Z
line/disc• Thin only
MyofilamentsMyofilaments Thick filaments: myosinThick filaments: myosin
““cross-bridges”cross-bridges”
Fig. 10-7
Contraction: myosin head
changes shape & will grab onto actin…and
pull it toward M-
line
MyofilamentsMyofilaments Thin filaments: 3 types of protein Thin filaments: 3 types of protein
moleculesmolecules– actin actin – TropomyosinTropomyosin– TroponinTroponin
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
Connective Tissue Connective Tissue WrappingsWrappings PerimysiumPerimysium
– Peri = around (central layer)Peri = around (central layer)– Divides muscle into Divides muscle into
compartments:compartments: Fascicle = Fascicle = bundlebundle of muscle fibers of muscle fibers
(cells)(cells)
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)
Fig. 10-1
Connective Tissues, cont.Connective Tissues, cont.
Layers continuous & interwoven Layers continuous & interwoven – blend into one another– blend into one another
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 bones or
other musclesother muscles
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!
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Figure 12.4 Connective tissue coverings of skeletal muscle.
EpimysiumBone
Tendon
Blood vessel
Perimysium wrapping a fascicle
Epimysium
Perimysium
Endomysium
Muscle fiberwithin afascicle
Endomysium(between individualmuscle fibers)
Muscle fiber
PerimysiumFascicle
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)
How Muscles How Muscles Contract: Contract:
DVDDVD
Neuromuscular JunctionNeuromuscular Junction
Junction of motor neuron & a muscle Junction of motor neuron & a muscle fiber fiber
MOTOR Neuron MOTOR Neuron —elongated portion = —elongated portion = axonaxon– synaptic terminalssynaptic terminals– synaptic cleftsynaptic cleft
Neuromuscular JunctionNeuromuscular Junction
Synaptic terminalsSynaptic terminals– synaptic vesicles synaptic vesicles
Filled with acetylcholine (ACh)Filled with acetylcholine (ACh)– Neurotransmitter Neurotransmitter – Release triggers muscle contractionRelease triggers muscle contraction
motor end plate motor end plate – Sarcolemma, has Sarcolemma, has receptorsreceptors to bind ACh to bind ACh
Neuromuscular JunctionNeuromuscular Junction
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
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Figure 12.5 The neuromuscular junction.
Synaptic vesiclecontaining ACh
MitochondrionSarcolemma
Axon terminal ofmotor neuron
Junctional foldsof sarcolemma
AChreceptors
ACh
Fusingsynapticvesicles
Sarcoplasmof muscle fiber
Synapticcleft
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Figure 12.6 Photomicrograph of neuromuscular junctions (750).
Terminalbranch ofan axon
Axonterminal atneuromuscularjunction
Muscle fibers
Fig. 10-10
Fig. 10-10
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Figure 12.6 Photomicrograph of neuromuscular junctions (750).
Terminalbranch ofan axon
Axonterminal atneuromuscularjunction
Muscle fibers
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Review Figure 12.1
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Review Figure 12.2
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Review Figure 12.3
Nucleus
Actionpotential
Junctionalfolds of thesarcolemma
Part of amyofibril