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54 Cards in this Set
- Front
- Back
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Muscle makes up what percentage of body mass?
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50%
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What are the four functions of muscle?
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1. Movement
2. Maintenance of Posture 3. Joint Stablization 4. Heat Generation |
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Maintenance of Posture
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enables the body to remain sitting or standing
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Joint stabilization
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Muscle tone provides stability and strength for joints
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Heat Generation
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When muscle contracts, the action produces heat that helps maintain normal body temperature
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What are four muscle characteristics that help distinguish this tissue from other tissues?
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1. Contractility- Mucles contracts forcefully
2. Excitability- Electrical nerve impulses stimulates the muscle cells 3. Extensibility-can be stretched back to it's original length by contraction by an opposing muscle 4. Elasticity-can recover to resume it's resting length |
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What are the three types of muscle tissue?
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1. Skeletal
2. Cardiac 3. Smooth |
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Similarities between muscle tissues
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1. Smooth and skeletal muscle cells are called fibers because they are highly elongated
2. Muscle contraction depends on myofilaments, made of actin and myosin 3. The plasma membrane of muscle cells is called a sarcolemma 4. The cytoplasm is called sarcoplasm |
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Skeletal muscle makes up what percentage of our body wieght?
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40%
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Where can we find cardiac muscle tissue?
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It occurs only in the walls of the heart
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Where can we find smooth muscle tissue?
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Occupies the walls of hallow organs
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Skeletal muscle is made up of what?
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1. Muscle cells (fibers)
2. Connective tissue 3. Blood vessels 4. Nerves |
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What are the three shealths that make up the connective tissue of skeletal muscle?
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From external to internal:
1. epimysium 2. perimysium 3. endomysium These are shealths of connective tissue that hold a skeletal muscle and it's constituents bundles and fibers together |
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Epimysium
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an "overcoat" of dense irregular connective tissue that surrounds the whole muscle (organ)
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perimysium
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within each skeletal muscle, individual muscle fibers are grouped into fascicles that resemble bundles of sticks, which are surrounded by perimysium
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endomysium
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within each fascicle, each muscle fiber is surrounded by a fine shealthof connective tissue consisting of mostly of reticular fibers(endomysium)
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How are the sheaths and tendons connected?
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All the sheaths are continuously connected with the tendons that join muscles to bones
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What happens when muscles contract?
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When muscle contracts, the sheaths are pulled, which in turn transmit the force to the bone being moved.
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In addition to movement, what do sheaths provide muscle?
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Sheaths provide
1. Natural Elasticity 2. Carry blood vessels and nerves that serve the muscle fibers |
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How many nerves and blood vessels supply one skeletal muscle?
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Each skeletal muscle is supplied by
1. one nerve 2. one artery 3. one or more veins |
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Structural relationship between muscles and bones?
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Most skeletal muscle run from one bone to another crossing at least one movable joint.
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What happens to bones that are connected to the muscle?
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When a muscle contracts, it causes one of these bones to move while the other bone usually remains fixed.
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The origin of skeletal muscles
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Proximal
less movable |
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The insertion of skeletal muscles
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distal
more movable attachment |
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What are the muscles that span two or more joints called?
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biarticular and multi-joint muscles
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How do the muscles attach to the origins and insertions?
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Strong connective tissue attach muscles to their origins and insertions
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Direct attachments
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the attaching strands of connective tissue are so short that the muscles fascicles themselves appear to abut the bone
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Indirect attachments
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the connective tissue extends well beyond the muscle to form a rope-like tendon or a flat sheet called aponeurosis
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What is the flat sheet that forms of connective tissue that forms indirect attachments?
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aponeurosis
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What occurs more commonly? Indirect or direct attachments
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indirect attachments
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In indirect attachements, what three types of raised bone markings are often present where tendons meet the bones
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1. tubercles
2. trochanters 3. crests |
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Where do tendons and aponeurosis attach to?
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1. Most attach to bone
2. Some attach to a. skin b. cartilage c. sheets of fascia d. raphe- seam of fibrous tissue |
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What are some characteristics of skeletal muscle? Shape and Size
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1. They are long and cylindrical
2. size: huge; 10-100 um ( up to 10 times that the average body cell) |
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Why are skeletal muscle fibers not considered the biggest cells?
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fibers are not considered the biggest cells because each one is actually formed by the fusion of hundreds of embryonic cells.
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Why does a skeletal muscle fiber contain many nuclei? And where are the nuclei located?
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The skeletal muscle fibers are formed by the fusion of hundreds of embryonic cells. They are peripherally located on the fiber.
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What are the light and dark stripes of the skeletal muscle fiber called?
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Striations
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What are the striations in the skeletal muscle caused by?
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Striations:
result from the internal structure of the long rodes called myofibrils within the sacroplasm |
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Structural characteristics of myofibrils?
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They are unbranched cylinders that are present in large numbers. They make up 80% of the sacroplasm
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Are myofibrils considered special to muscle fibers?
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Yes. Myofibrils can be considered specialized contractile cellular organelles unique to muscle fibers
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Definition of myofibril
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A myofibril is a long row of repeating segments called sacromeres
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sacromere
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Most basic unit of contraction in skeletal muscle
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What are the z discs represent?
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Z discs represent the boundaries of the sacromeres
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Actin
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Thin filaments are fine myofilaments that are attached to each Z-disc and extend toward the center of the sacromere
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Myosin
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Thick filaments are cylindrical bundles found in the center of sacromere and overlap the inner ends of the thin filaments
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What part the thick myosin filament stud both ends of the thick filament?
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Myosin heads or cross bridges
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What do A bands correspond with?
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the full length of the thick (myosin) filaments and they also include the inner ends of the thin filaments where they overlap
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What is the H zone?
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This is the central part of the A band where no thin filaments occur
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M Line
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M Line is in the center of the H zone. It contains tiny rods that hold adajacent thick filaments together.
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I bands
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are the regions where the only thin filaments occur
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Mechanism of the skeletal muscle contraction
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sliding filament theory
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Sliding filament theory
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contraction that results as the myosin heads of the thick filaments attach to the thin filaments at both ends of the sarcomere and pull the thin filaments toward the center of the sarcomere by the swiveling inward
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What happens in one cycle of a single skeletal muscle contraction?
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After a myosin head pivots at its "hinge", it lets go "recocks" binds to the thin filament farther along it's length, and pivots again. This cycle is repeated many times during a single contraction.
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What initiates the cycle in a single skeletal muscle contraction?
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the binding of calcium ions to the thin filaments and is powered by ATP
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What happens when the Z discs are pulled together?
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1. Sacromere is shorten
2. I bands narrow 3. H zones disappear completely 4. A bands stay the same width because the length of the thick filaments does not change |
