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20 Cards in this Set
- Front
- Back
Muscle Tissue
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Three types
Skeletal Cardiac Smooth Myo, Mys, Sarco- prefixes for muscle |
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Types of Muscle Tissue
Skeletal muscles |
Organs attached to bones and skin
Elongated CELLS CALLED MUSCLE FIBERS STIATED (striped) VOLUNTARY (i.e, conscious control) Contract rapidly: tire easily: powerful Require nervous system stimulation |
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Types of Muscle Tissue
Cardiac Muscle |
Only in heart: bulk of heart walls
STRIATED Can contact without nervous system stimulation INVOLUNTARY |
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Types of Muscle Tissue
Smooth muscle |
In wals of hollow organs, e.g., stomach, urinary bladder, and airway *So sometimes KNOWN AS VISCERAL MUSCLE*
NOT STRIATED Can contract without nervous system stimulation INVOLUNTARY |
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SPECIAL CHARACTERISTICS of muscle tissue
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Excitability(responsiveness): Ability to receive and respond to stimuli
Contractility: ability to shorten forcibly when stimulated • Extensibility: ability to be stretched • Elasticity: ability to recoil to resting length |
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Muscle Functions
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FOUR IMPORTANTT FUNCTIONS
-MOVEMENT OF BONES or fluids (e.g., blood) -maintaining posture and body position -Stabilizing joints -Heat generation (especially skeletal muscle) |
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Skeletal Muscle
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• Each muscle served by one artery, one nerve, and one or more veins
– Enter/exit near central part and branch through connective tissue sheaths EVERY SKELETAL MUSCLE FIBER SUPPLIED BY NERVE ENDING THAT CONTROLS ITS ACTIVITY |
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Skeletal Muscle
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• Connective tissue sheaths of skeletal muscle
– Support cells; reinforce whole muscle – External to internal • EPIMYSIUM: dense irregular connective tissue surrounding entire muscle; may blend with fascia • PERIMYSIUM: fibrous connective tissue surrounding fascicles (groups of muscle fibers) • ENDOMYSIUM: fine areolar connective tissue surrounding each muscle fiber |
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Skeletal Muscle: Attachments
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• Attach in at least two places
– Insertion – movable bone – Origin – immovable (less movable) bone • Attachments direct or indirect – DIRECT—epimysium fused to periosteum of bone or perichondrium of cartilage – iINDIRECT—connective tissue wrappings extend beyond muscle as ropelike TENDON OR SHEETLIKE APONEUROSIS |
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Microscopic Anatomy of a Skeletal Muscle Fiber
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• Long, cylindrical cell
– 10 to 100 µm in diameter; up to 30 cm long • Multiple peripheral nuclei • SARCOLEMMA= plasma membrane • SARCOPLASM = cytoplasm – Glycosomes for glycogen storage, MYOGLOBIN for O2 storage • Modified structures: myofibrils, sarcoplasmic reticulum, and T tubules |
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Myofibrils
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Contain SARCOMERES- CONTRACTILE UNITS
-sacromeres contain MYOFILAMENTS Exibit STRIATIONS- perfectly aligned repeating series of DARK A BANDS AND LIGHT I BANDS |
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Striations
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H ZONE: lighter region in midsection of dark A band where filaments do not overlap
M LINE: line of protein myomesin bisect H zone Z DISC(LINE):coin-shaped sheet of proteins on midline of light i band that anchors thin filaments and connects myofibrils to one another THICK FILAMENTS: run entire length of an A band THIN FILAMENTS: run legth of i band and partway into A band SARCOMERE: region between two successive Z disc |
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Sarcomere
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• Smallest contractile unit (FUNCTIONAL UNIT) of muscle fiber
• Align along myofibril like boxcars of train • Contains A band with ½ I band at each end • Composed of thick and thin MYOFILAMENTS made of contractile proteins |
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MYOFIBRIL Banding pattern
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• Orderly arrangement of actin and myosin myofilaments within sarcomere
– Actin myofilaments = thin filaments • Extend across I band and partway in A band • Anchored to Z discs – Myosin myofilaments = thick filaments |
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Ultrastructure of THICK FILAMENT
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• Composed of protein myosin
• Each composed of 2 heavy and four light polypeptide chains – MYOSIN TAILS contain 2 interwoven, heavy polypeptide chains – MYOSIN HEADS contain 2 smaller, light polypeptide chains that act as cross bridges during contraction _ BINDING SITES FOR ACTIN OF THIN FILAMENTS _ BINDING SITES FOR ATP _ ATPASE ENZYMES` |
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Ultrastructure of THIN FILAMENT
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• Twisted double strand of fibrous protein
F actin • F actin consists of G (GLOBULAR) ACTIN SUBUNITS • G actin bears active sites for myosin head attachment during contraction • ****Tropomyosin and troponin - regulatory proteins bound to actin |
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Structure of Myofibril
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• Elastic filament
– Composed of proteinTITIN – Holds thick filaments in place; helps recoil after stretch; resists |
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Sarcoplasmic Reticulum (SR)
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• Network of smooth endoplasmic reticulum SURROUNDING EACH MYOFIBRIL•
Functions in regulation of intracellular Ca2+ levels – STORES AND RELEASES Ca2+ |
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T Tubules
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CONTINUATIONS OF SARCOLEMMA
PENETRATE CELL"S INTERIOR at each A band- I band junction associate with paired terminal cisterns to form TRIADS that encircle each sarcomere |
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Triad Relationships
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T TUBULES CONDUCT IMPULSES DEEP INTO MUSCLE FIBER;EVERY SARCOMERE
T tubule integral proteins act asVOLTAGE SENSORSs and change shape in response to voltage changes SR integral proteins are CHANNELS THAT RELEASE Ca2+FROM SR CISTERNSwhen voltage sensors change shape |