muscle system
DESCRIPTION
Muscle System. Ch 9. Muscle Properties. 4 basic properties Contractability Excitability Extensibility Elasticity. Contractability. Cells capable of decreasing along a longitudinal axis Shorten & thicken Produce force Pull or create tension. Contractability. Excitability. - PowerPoint PPT PresentationTRANSCRIPT
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Muscle System
Ch 9
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Muscle Properties
• 4 basic properties– Contractability– Excitability– Extensibility– Elasticity
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Contractability
• Cells capable of decreasing along a longitudinal axis– Shorten & thicken
• Produce force– Pull or create tension
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Contractability
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Excitability
• Ability to respond to external stimulation
• Stimulation initiated by – Hormonal cues– nerves
• Motor nerves
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Extensibility
• Ability to “stretch” without loss of function
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Elasticity
• Ability to regain original shape following contraction
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Muscle Types
• Skeletal• Cardiac• Smooth
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Skeletal
• Aka muscle fiber• Primary muscle type
– 700+
• Voluntary – Only consciously controlled tissue
• Move & stabilize the skeleton• Striated
– Contractile proteins produce movement (contraction), striated in appearance
• Large, multinucleate cells• Long thin cells= myofibers• Some regeneration
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Striation
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Skeletal Muscle Function
• By mean of contractions..
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Skeletal Muscle Functions
• Produce skeletal movement
• Maintain posture & position
• Support soft tissue (pelvic floor & abdominal wall)
• Regulate entering & exiting of material– Digestive & urinary tract
• Thermogenic– Produce body heat
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Motor Control• Controlled by higher
brain regions (Cerebrum)
• Allow for conscious control of muscles
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Smooth• Aka visceral• Non-striated aka smooth• Involuntary
– Not consciously controlled
• Small spindle shaped cells– Microfibers with random arrangement
• Uninucleate• Regenerative• Functions in transporting fluids & solids through the body
– Ex digestive system, urinary structures, blood vessels, glands, reproductive tract
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Cardiac• Involuntary striated
– Self stimulating• Only in heart• Small, uninucleate,
interconnected, branched cells• Intercalated discs
– Visible cellular connections• Gap junctions• Desmosomes
• Functions to push blood through blood vessels
• No regeneration
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Cardiac
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Skeletal Muscle Anatomy
• Specialized cells- Myofibers
• Long slender fiber like cells
• Mature cells multinucleate– NOT capable of mitotic division
• Cellular development– Fusion of many embryonic stem cells form
long multinucleate cells• myoblasts
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Myofiber
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Myofibers
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Skeletal Muscle Cellular Development
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Myofibers
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Myofiber Structure
• Sarcolemma – Myofiber cell membrane
• Sarcoplasm– Myofiber cytoplasm
• Made up of bundles of myofibrils– Made up of micrfilaments aka myofilaments
• Satallite cells– Muscle stem cells– Resident myoblasts in adult tissue– Tissue repair
• Fascicle– Connective tissue holds together for organization– Contains bundles of myofibers
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Myofiber
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Sarcolemma
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Sarcoplasm
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Satellite Cells
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Myofibers are made of bundles of Myofibrils
Aka Fascicle
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Myofibrils are bundles of Myofilaments
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Muscle Connective Tissue
• Connective tissue surrounds, supports, & attaches muscle
• 3 layers of connective tissue– Endomysium– Perimysium– Epimysium
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Endomysium
• “Within”
• CT surrounding & binding together individual myofibers
• Delicate network of reticular fibers– Holds myofibers together– Supports blood vessels
• House satellite cells
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Endomysium surrounds & binds together individual myofibers
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Endomysium
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Endomysium- Normal Cells
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Perimysium• “around”• CT surrounding & binding groups of
myofibers• Fascicles
– Stringiness of meat• Collagen & elastic fibers• Houses blood vessels & nerves
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Perimysium- Cross Section
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Perimysium- Longitudinal Section
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Perimysium anchors blood vessels & nerves
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Perimysium bundles a fascicle
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Epimysium• “above”• Dense irregular CT • Surrounds & binds fascicles together• Holds together Individual muscles into discrete units
– Ex biceps, triceps, deltoid
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Epimysium
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Tendons & Aponeurosis
• CT attaching– Muscle to bone– Muscle into CT of another muscle
• Combination of CT fibers from all levels of muscle organization– Endomysium– Perimysium– Epimysium
• CT fibers are continuous w/ periosteum & osseous matrix= strong muscle attachments– Bones more likely to break before tendon tears away from bone
• All CTs merge to form attachments– Tendon- strong cord or rope– Aponeurosis- flattened sheet
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Tendon
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Aponeurosis
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Attachment
• Origin– Point of attachment to the fixed bone– Site that remains stationary during muscle
contraction– Typically proximal
• Insertion– Point of attachment to the moving bone– Typically distal
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Deltoid
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Teres Major
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Teres Minor
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Muscle function
• Prime movers & Agonists– Key muscle in motion, primarily responsible
• Antagonists– “Reverse” motion
• Synergists– Aid prime mover
• Fixators– Specialized synergists– Immobilize origin of prime mover– Maximize motion
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Prime Mover aka AgonistBiceps Brachii
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Antagonist- Triceps Brachii
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Synergist- Brachialis
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Synergist- Pronator Teres
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Supinator