Muscle System
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Transcript of Muscle System
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
• Ability to respond to external stimulation
• Stimulation initiated by – Hormonal cues– nerves
• Motor nerves
Extensibility
• Ability to “stretch” without loss of function
Elasticity
• Ability to regain original shape following contraction
Muscle Types
• Skeletal• Cardiac• Smooth
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
Striation
Skeletal Muscle Function
• By mean of contractions..
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
Motor Control• Controlled by higher
brain regions (Cerebrum)
• Allow for conscious control of muscles
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
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
Cardiac
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
Myofiber
Myofibers
Skeletal Muscle Cellular Development
Myofibers
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
Myofiber
Sarcolemma
Sarcoplasm
Satellite Cells
Myofibers are made of bundles of Myofibrils
Aka Fascicle
Myofibrils are bundles of Myofilaments
Muscle Connective Tissue
• Connective tissue surrounds, supports, & attaches muscle
• 3 layers of connective tissue– Endomysium– Perimysium– Epimysium
Endomysium
• “Within”
• CT surrounding & binding together individual myofibers
• Delicate network of reticular fibers– Holds myofibers together– Supports blood vessels
• House satellite cells
Endomysium surrounds & binds together individual myofibers
Endomysium
Endomysium- Normal Cells
Perimysium• “around”• CT surrounding & binding groups of
myofibers• Fascicles
– Stringiness of meat• Collagen & elastic fibers• Houses blood vessels & nerves
Perimysium- Cross Section
Perimysium- Longitudinal Section
Perimysium anchors blood vessels & nerves
Perimysium bundles a fascicle
Epimysium• “above”• Dense irregular CT • Surrounds & binds fascicles together• Holds together Individual muscles into discrete units
– Ex biceps, triceps, deltoid
Epimysium
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
Tendon
Aponeurosis
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
Deltoid
Teres Major
Teres Minor
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
Prime Mover aka AgonistBiceps Brachii
Antagonist- Triceps Brachii
Synergist- Brachialis
Synergist- Pronator Teres
Supinator