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48 Cards in this Set
- Front
- Back
What are the three muscle types?
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1) skeletal
2) cardiac 3) smooth |
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Histology of skeletal muscles
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- Longitudinal section: long, multinucleated, nucleus at edge just under sarcolemma, may appear to be different sizes according to section, striated
- Cross: do not see striations, oval, nuclei at edge, visible sarcolemma and sarcoplasm |
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Histology of cardiac muscles
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- Longitudinal: long, looks cylindrical but is individual cells with central nuclei, intercalated disks, striated
-Cross: central nuclei, striations not apparent |
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Histology of smooth muscles
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- Longitudinal: appear in sheets, central nuclei, tapered cells, no striations
- Cross: central nuclei (may/may not see), ovalish in varying size according to section |
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What is the motor unit of a skeletal muscle comprised of?
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- neuron
- axon - all the muscle fibers it innervates |
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What are the connective tissues of skeletal muscle?
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- endomysium: delicate, loose connective tissue around each muscle fiber
- perimysium: surrounds bundles of muscle fibers (fascicles) - Epimysium: dense connective tissue surrounds muscle |
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What is the importance of external lamina/basement membrane in regeneration?
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- as long as the lamina is fairly intact satellite cells can regenerate damaged muscles
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What are the 3 types of fibers?
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1) Red (type I)
2) White (type IIb) 3) Intermediate fibers (type IIa) |
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Red fibers (type I)
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- high mitochondria
- strong NADH/succinic dehydrogenase enzyme activity - slow-twitch - resist fatigue - less muscle tension - continuous activity |
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White fibers (type IIb)
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- low mitochondria
- weak NADH/succinic dehydrogenase reaction - fast twitch - fatigue easily - generate a lot of tension |
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Intermediate fibers (type IIa)
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- in between red and white fibers
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Organization of skeletal muscle
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- muscle fibers contain many myofibrils
- myofibrils are made up of myosin and actin (myofilaments) - myofilaments are arranged in specific patters in sarcomeres |
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A band of myofilaments
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-overlapping area of actin and myosin
- middle of sarcomere - stains dark |
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H band of myofilaments
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- only myosin
- bisects A band |
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M line of myofilaments
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- myosin and network protein
- bisects H band |
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I band of myofilaments
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- only actin
- half is part of sarcomere (the other half is part of a different sarcomere) |
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Z band of myofilaments
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- bisects the I band
- Z band to Z band is the sarcomere |
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What are the 3 subunits of troponin?
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C: calcium binding
I: inhibitor T: troppomyosin binding |
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Where is tropomyosin located?
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- on top of globular actin chain
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What configuration is troponin/tropomyosin in when muscle is relaxed?
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- T subunit of Troponin is bound to tropomyosin
- tropomyosin is on top of actin - myosin head cannot bind to actin |
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What happens during a muscle contraction?
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- Ca influx through the sarcoplasmic reticulum and T-tubulues (tria)
- Ca binds to C subunit and induces conformation change - Myosin able to attach to actin, moves through ATP |
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What happens in the transport of a Nerve Impulse in muscle contraction?
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- Nerve impulse arrives at motor end plate by motor neuron
- Axon sent to skeletal muscle (branches to several fibers) - Action potential depolarizes membrane - Action potential generated in the muscle cell (continues downwards b/c T-tubules) - Ca released from sarcoplasmic reticulum - Ca activate contractile proteins (actin/myosin) - Ca returned to sarcoplasmic reticulum |
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What is the muscle spindle?
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- receptor unit in muscle that contains special muscle fibers and neuron terminals surrounded by a capsule
- responds to stretch and controls muscle coordination - provides information on muscle length |
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What are the two types of special muscle fibers within a muscle spindle?
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- Nuclear bag fibers
- Nuclear chain fibers |
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What is the golgi tendon organs
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- encapsulated nerve endings in the tendon that respond to stretch
- only contain afferent neurons - provides information on tension development |
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What are intercalated discs in cardiac muscle?
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- end to end junctions between each cell
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What are the 3 types of intercalated discs in cardiac muscle?
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1) Fascia adherents: sheets
2) Macula adherents: desmosomes 3) Gap junctions: allows electrical passing |
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What comprises a fiber in cardiac muscle?
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- many mononucleated cells
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What are some specialized features of cardiac muscle?
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- cells branch
- mitochondria are very large (could be length of a sarcomere) - Sarcoplasmic reticulum is well developed and organized into diads at the Z line - central nuclei, could be binucleated - cannot regenerate (creates connective tissue) - Heart will beat without innervation (intrinsic conducting system) |
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How are the contractile proteins of smooth muscles different?
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- not very organized
- they are anchored at the edges of the cell, called dense bodies - thin filaments (actin) are attached to the dense bodies that contain the actin binding proteins: alpha-actinin and desmin |
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What do dense bodies contain?
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-vinculin
-talin -desmin |
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What shape do smooth muscle cells have?
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- spindle shaped with a central nuclei that form to cell shape
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What supplies the energy for contraction in smooth muscle?
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- mitochondria,usually around the nucleus
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How does the contraction signal spread in smooth muscle?
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- through gap junctions (nexus junctions)
- cells function together |
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What are the invaginations in smooth muscle called that control the entry of Ca?
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- caveoli
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What do smooth muscle contractions result from?
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- mechanical impulses
- electrical depolarization - biochemical stimuli |
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Where is smooth muscle found?
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- hollow visceral organs
- blood vessel walls |
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Can smooth muscle replace damaged cells?
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- yes through mitosis
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Where is the T-tubule located in skeletal muscles, describe its composition.
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- A/I junction
- Triad: contains 2 terminal cisternae (where sarcoplasmic reticulum joins) and 1 T-tubule (invagination of plasma membrane) |
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Where are satellite cells of skeletal muscle located? what do they do?
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- between plasma membrane and basement membrane
- dormant stem cells that can proliferate after injury to produce myoblasts |
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What parts of the sarcomere shorten during contraction?
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- I and H bands
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What is the motor end plate/neuromuscular junction of skeletal muscle
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- axonal ending of motor neuron
- receptor region of striated muscle fibers that receives innervation |
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What is the primary cleft in skeletal muscle?
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- a shallow depression in the muscle cells where the axon terminal lies
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What are secondary or subneural clefts in skeletal muscle?
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- narrow folds formed by the sarcolemma
- increase receptor surface area of the muscle - presence of basement membrane does not interfere with synaptic transmission |
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What is the arrangement of nuclei from nuclear bag fibers within a muscle spindle? (skeletal muscle)
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- nuclei aggregate in the expanded middle region of the spindle
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What is the arrangement of nuclei from nuclear chain fibers within a muscle spindle? (skeletal muscle)
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- nuclei are arranged linearly
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How are the T-tubules organized in cardiac muscle?
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- diads foudn at the Z line
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Is the T-tubule system found in smooth muscles?
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No, have caveoli to control Ca entrance
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