ANSWER THE ESSAYS AND THE BULLET (-) QUESTIONS
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APLECTURE13MUSCULARSYSTEM.pptMuscular System
Muscles
- Rippling muscles
- Dominant tissue heart
- Walls hollow organs in body
- ½ body mass
Function of Muscles
- Contraction
- Shortening
- Unique to muscle tissue
- Body movement
Muscle Types
- Skeletal
- Cardiac
- Smooth
Similarities
- all muscle cells elongated
- muscle cells = muscle fibers
- able to shorten
- Myofilaments
- Myo, mys, sarc = muscle
- Sarcoplasm = cytoplasm of muscle cells
Skeletal Muscle
- Skeletal muscle fibers (cells) packed into skeletal muscles (organs)
- Attach to body’s skeleton
- Multinucleate cells
- Largest muscle fiber
- Striated
- Voluntary muscle
- Conscious control
- Also activated by reflexes
- Contracts rapidly w/ great force
- Tires easily
Skeletal Muscle
- Muscle Fiber
- Cell
- Bundled by connective tissue
- Provides strength and support to muscle
Skeletal Muscle
- Endomysium
- Connective tissue sheath
- Encloses muscle fibers
Skeletal Muscle
- Perimysium
- Several sheathed muscle fibers wrapped by fibrous membrane
Skeletal Muscle
- Fasicle
- Bundle of fibers
Skeletal Muscle
- Epimysium
- Many fasicles bound together by tough overcoat
- Connective tissue
- Covers entire muscle
- Blend into tendons or aponeuroses
Skeletal Muscle
- Tendons
- Strong cords eipmysia blend into
- Anchor muscles
- Durability
- Conserve space
- Tough collagenic fibers
- Cross rough bony projections that would tear muscle
Skeletal Muscle
- Aponeuroses
- Sheetlike structure attaches muscles indirectly to bones, cartilage, or connective tissue coverings of muscles
Smooth Muscle
- Nonstriated
- Involuntary
- Not under conscious control
- Walls hollow visceral organs
- Stomach, urinary bladder, respiratory passageways
- Propels substances along
- Spindle shaped cells
- Single nucleus
Smooth Muscle
- Arranged in sheets or layers
- Usually 2 layers 1 – circularly 2 – longitudinally
- Alternating contractions
- Contraction slow and sustained
Cardiac Muscle
- Heart
- Pump propel blood through blood vessels
- Striated
- Involuntary
- Cardiac fibers cushioned by connective tissue
- Arranged in spirals or figure 8 bundles
- Branching cells joined by intercalated discs
- Contracts steady rate set by pacemaker
- Stimulated by nervous system
Muscle Functions
- Produces movement
- Maintains posture
- Stabilizes joints
- Generates heat
Producing Movement
- Movements result of muscle contraction
- Skeletal - mobility
- Respond quickly to changes in external environment
- Express emotions
- Cardiac – circulate blood
- Smooth – force fluid and substances through body channels
Maintaining Posture
- Tiny adjustments
- Maintain erect or seated posture
- Against pull of gravity
Stabilizing Joints
- Tendons reinforce and stabilize joints
Generating Heat
- By-product muscle activity
- ATP used to power muscle contraction
- 75% energy lost as heat
- Mostly skeletal muscle
- 40% of body mass
Microscopic Anatomy of Skeletal Muscle
- Cells multinucleate
- Sarcolemma
- Plasma membrane
- Myofibrils
- Ribbonlike organelles
- Push nuclei to side
- Striped appearance
- Alternating light (I) and dark (A) bands
Microscopic Anatomy of Skeletal Muscle
- Light I Band
- Z disc – midline interruption
- Dark A Band
- H zone – light central area
Microscopic Anatomy of Skeletal Muscle
- Sarcomeres
- Contractile units
- Aligned along length of myofibrils
- Myofilaments
- Produce banding pattern
Microscopic Anatomy of Skeletal Muscle
- Thick Filaments
- Larger
- Myosin filaments
- Protein myosin
- ATPase enzymes –split ATP to generate power for muscle contraction
- Extend entire length of A band
- Myosin heads
- Cross bridges
- Link thick and thin filaments during contraction
Microscopic Anatomy of Skeletal Muscle
- Thin Filaments
- Actin filaments
- Protein actin
- Regulatory proteins for binding to myosin head
- Anchored to Z disc
- H zone
- Lacks actin filaments
- Bare zone
Microscopic Anatomy of Skeletal Muscle
- Sarcoplasmic reticulum
- Smooth ER
- Surround myofibrils
- Stores calcium and releases it during muscle contraction
- Calcium is the go signal for contraction
