muscular system - fisiokinesiterapia · •organization of the sarcomere •thick filaments =...
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Slide 2.1
Muscular System
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The Muscular SystemThe Muscular System
Slide 6.1
• Muscles are responsible for body movement
• Three types are found in the body•Skeletal muscle**
•Cardiac muscle
•Smooth muscle
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Types of MuscleTypes of Muscle
Three types of muscle
Skeletal Cardiac Smooth
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Functions of Skeletal MusclesFunctions of Skeletal Muscles
Slide 6.1
• Make up “flesh” of the body
• Maintain Posture
• Voluntary movement
• Aid in breathing, eating, speech
• Provide facial expression
• Generate reflexes
• Produce body heat
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Characteristics of Skeletal MusclesCharacteristics of Skeletal Muscles
Slide 6.2
• Muscle cells are elongated (muscle cell = muscle fiber)
• Muscles are specialized to contract
• Terminology:•Prefix myo, mys refer to muscle
•Prefix sarco refers to flesh
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Characteristics of Skeletal MusclesCharacteristics of Skeletal Muscles
Slide 6.3
• Most are attached by tendons to bones
• Cells are multinucleate
• Striated – have visible banding
• Voluntary – subject to conscious control
• Muscles and their fibers are wrapped by connective tissue
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Connective Tissue Wrappings ofConnective Tissue Wrappings ofSkeletal MuscleSkeletal Muscle
Slide 6.4a
• Endomysium –around single muscle fiber
• Perimysium –around a fascicle (bundle) of fibers Figure 6.1
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Connective Tissue Wrappings ofConnective Tissue Wrappings ofSkeletal MuscleSkeletal Muscle
Slide 6.4b
• Epimysium –covers the entire skeletal muscle
• Fascia – on the outside of the epimysium
Figure 6.1
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Skeletal Muscle AttachmentsSkeletal Muscle Attachments Slide 6.5
• Epimysium blends into a connective tissue attachment•Tendon – cord-like
structure•Aponeurosis –
sheet-like structure
Fig. 7.2abc
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Skeletal Muscle AttachmentsSkeletal Muscle Attachments
Slide 6.5
• Sites of muscle attachment•Bones•Cartilages•C. T. coverings• i.e., aponeuroses
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Microscopic Anatomy of SkeletalMicroscopic Anatomy of SkeletalMuscleMuscle
Slide 6.9a
• Cells are multinucleate
• Nuclei are deep to the sarcolemma
Figure 6.3a
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Microscopic AnatomyMicroscopic Anatomy
Slide 6.9b
• Sarcolemma – specialized plasma membrane
• Sarcoplasmic reticulum – specialized smooth E.R.• Stores Ca++
• Required for contraction
Figure 6.3a
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Microscopic AnatomyMicroscopic Anatomy
Slide 6.10a
• Myofibril: organelle unique to muscle•Bundles of myofilaments
•Myofibrils alignment produces distinct bands
• I band = light band
•A band = dark band
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Microscopic AnatomyMicroscopic Anatomy
Slide 6.10a
• Banding Pattern depends on arrangement of proteins in myofibrils•Actin: thin
•A and I bands
•Myosin: thick
•A bands
Figure 6.3b
A-bandI-band
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Microscopic AnatomyMicroscopic Anatomy
Slide 6.10b
• Sarcomere•Contractile subunit of a muscle fiber•From “Z to Z”• One A band +• Two “half” I
bands
Figure 6.3b
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Microscopic AnatomyMicroscopic Anatomy
Slide 6.11a
• Organization of the sarcomere•Thick filaments = myosin filaments•Composed of the protein myosin•Has ATP-ase enzymes
Figure 6.3c
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Microscopic AnatomyMicroscopic Anatomy
Slide 6.11b
• Organization of the sarcomere, con’t…•Thin filaments = actin filaments•Composed of the protein actin
Figure 6.3c
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Microscopic AnatomyMicroscopic Anatomy
Slide 6.12a
• Myosin filaments have heads (extensions, or cross bridges)
• Myosin and actin overlap
Figure 6.3d
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Microscopic AnatomyMicroscopic Anatomy
Slide 6.12b
• At rest, there is a bare [“H”] zone that lacks actin filaments
Figure 6.3d
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Properties of Skeletal MuscleProperties of Skeletal Muscle
Slide 6.13
• Irritability – ability to receive and respond to a stimulus
• Contractility – ability to shorten when an adequate stimulus is received
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Nerve Stimulus to MusclesNerve Stimulus to Muscles
Slide 6.14
• Skeletal muscles require innervation
• Motor unit•One motor
neuron +•Muscle cells
innervated by that neuron
Figure 6.4a
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Nerve Stimulus to MusclesNerve Stimulus to Muscles
Slide 6.15a
• Neuromuscular junction:•communication
site between a motor neuron and a muscle fiber
Figure 6.5b
Fig. 7.5a
Motor Neuron
Neuromuscular Junction
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Nerve Stimulus to MusclesNerve Stimulus to Muscles
Slide 6.15b
• Synaptic cleft :gap between nerve and muscle•Nerve and
muscle do not make direct contact
Figure 6.5b
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Transmission of Nerve Impulse to Transmission of Nerve Impulse to MuscleMuscle
Slide 6.16a
• Neurotransmitter – chemical released by motor nerve • initiates contraction• Causes sarcolemma to depolarize
•For skeletal muscle: acetylcholine (Ach)
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Transmission of Nerve Impulse to Transmission of Nerve Impulse to MuscleMuscle
Slide 6.16a
• Action of Neurotransmitter•Crosses synaptic
cleft
•Attaches to receptors on the sarcolemma
Fig. 7.6
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Muscle ContractionMuscle Contraction• An electrochemical event
•Ach is the chemical
• Before contraction can occur, sarcolemma must be polarized•A polarized membrane is more “+” outside
and more “-” inside
• Movement of ions creates “action potential”• The ability to do work
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Muscle ContractionMuscle Contraction
Slide 6.16b
• Ach attaches to receptor sites
• Sarcolemma becomes permeable to sodium (Na+)
• Sodium rushes into the cell
• Initiates “sliding filament” process
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Muscle ContractionMuscle Contraction
Slide 6.16b
• Membrane of sarcoplasmic reticulum also depolarizes
• Ca++ ions are released
• Bind to sites on actin
• Open attachment sites for myosin
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The Sliding Filament Theory of The Sliding Filament Theory of Muscle ContractionMuscle Contraction
Slide 6.17a
• Depolarization allows myosin heads to attach to binding sites on actin• called
crossbridges• ATP required
Figure 6.7
Fig. 7.7a
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The Sliding Filament Theory of The Sliding Filament Theory of Muscle ContractionMuscle Contraction• Actin is pulled past
myosin by movement of heads• ATP required
• Myosin heads detach• ATP required
• Then bind to the next site on actin• ATP required
Fig. 7.7b
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The Sliding Filament Theory of The Sliding Filament Theory of Muscle ContractionMuscle Contraction• This continued
action causes a sliding of the actin along the myosin• I band narrows
• H zone narrows
• A band stays the same
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The Sliding Filament Theory of The Sliding Filament Theory of Muscle ContractionMuscle Contraction
Slide 6.17b
• Actin slides past myosin
• Results in shortening of the sarcomere• Muscle fiber has
thousands of sarcomeres
• All shorten at one time
• Muscle contractsFigure 6.7