Term
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Definition
| Contains thick (myosin) filaments, overlap of thick and thin filaments (potential sites of cross-bridge formation) |
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Term
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Definition
| Contains thin (actin) filaments, Z line...no thick filaments |
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Term
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Definition
| Bisect each I band, marking end of each sarcomere |
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Term
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Definition
| Center of each sarcomere...No thin filaments, thus no thick and thin filament overlap, no cross-bridge formation in this region |
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Term
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Definition
| Bisects the H Zone. Anchors central portion of the thick filaments together |
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Term
| What are the 3 major proteins of the thin filaments? |
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Definition
Actin Tropomyosion Troponin |
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Term
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Definition
| globular protein - polymerized into double-stranded, helical filamentous actin (F-actin) |
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Term
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Definition
| filamentous protein that blocks the myosin-binding sites on actin |
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Term
Define Troponin. What's the function of: TnT TnI TnC |
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Definition
Troponin: complex of 3 globular proteins, TnT, TnI, TnC TnT: attaches troponin complex to tropomyosin TnI: inhibits filament interaction - covers myosin binding site on actin TnC: Ca2++ binding protien for initiation of contraction |
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Term
| How many myosin molecules does the thick filament? |
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Definition
| about 200 myosin molecules |
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Term
Describe function of the thin filament proteins: alpha-actinin and CapZ(beta-actinin) Tropomodulin Nebulin |
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Definition
Actinin proteins: anchor and weave thin filaments into Z-line Tropomodulin: caps filament, maintains length Nebulin: associated with thin filaments to help align actin |
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Term
Describe the function of the thick filament proteins: Titin MyBP-C |
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Definition
Titin: extends into thick filaments from Z-lines. Flexibly stabiliezes thick filament position MyBP-C: links thick filaments and titin |
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Term
Describe the function of the M-line protein: M-protein (myomesin) |
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Definition
| M-protein (myomesin): links thick filaments to M-line |
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Term
Define: sarcolemma T-tubules sarcoplasmic reticulum terminal cisternae triads |
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Definition
Sarcolemma: muscle cell plasma membrane T-tubules: invaginations of sarcolemma into cell interior Sarcoplasmic reticulum: modified endoplasmic reticulum. Surrounds myofibrils Terminal cisternae: expansions of sarcoplasmic reticulum near T-tubules Triads: central t-tubule with 2 adjoining terminal cisternae, located at A-I band junction |
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Term
Muscular Dystrophy origin, role of dystrophin |
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Definition
X-linked genetic disorder of membrane-associated protein, dystrophin Duchenne Muscular Dystrophy (DMD) is the most common form, and involves a frameshift mutation of the dystrophin gene Dystrophin: Important component in a complex that stabilizes membrane structure, and forms a structural link between muscle fiber and surrounding basal lamina. |
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Term
What are 2 key proteins in determining phenotype of muscles? Without these 2 proteins the myoblast, would remain a simple fibroblast. |
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Definition
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Term
| What is the function of muscle satellite cells? |
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Definition
| Important in hypertrophy and repair of skeletal muscles. |
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Term
What is myostatin? What stage of development does myostatin work in? What happens if there is a myostatin mutation? |
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Definition
Myostatin is a growth factor that limits muscle tissue growth by slowing the addition of satellite cells. Myostatin works in development of myoblasts into the early myotube. In myostatin mutations, you get overly musclular organisms ("buff baby"). |
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Term
| What is the most important aspect of muscle fibers in respects to the strength of the muscles? |
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Definition
| Fiber diameter directly correlates with strength. |
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Term
During contraction of a muscle the following sarcomere areas are affected how? A band I band H band AI overlap |
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Definition
A band: constant I band: narrows H band: narrows AI overlap: increases |
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Term
| What cofactor is required for the proper function of ATPase in cross-bridge cycling? |
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Definition
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Term
Motor end plates are found on what type of muscle? |
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Definition
Motor end plates are only found on skeletal muscles, as these muscles are voluntary. Cardiac and smooth muscle lack motor end plates |
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Term
| What is the effect of botulinum toxin (BoTox)? |
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Definition
Botox prevents fusion of synaptic vesicles with presynaptic membrane and ACh release. |
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Term
| What is the role of ryanodine receptors (RyR)? |
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Definition
| Ca++ ions activatge ryanodine receptors (RyR) in SR terminal cisterna membranes to release stored Ca++ into cytosol |
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Term
| What prevents damage to a single nerve from causing complete loss of muscle function? |
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Definition
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Term
| Histochemical staining identifies mitochondria in muscle fibers by staining for what enzyme? |
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Definition
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Term
Compare and contrast red and white fibers in regards to the following: Type Speed Oxidative or Glycolytic Mitochondria or glycogen Speed of Fatigue Used for? |
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Definition
Red: Type 1, Slow, Oxidative, Abundant mito., slow to fatigue, used for postural muscles, endurance White: Type 2, fast, glycolytic, Abundant glycogen, quickly fatigued, used in limb muscles, for burst of activity |
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Term
| Muscular dystrophy clinical manifestations |
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Definition
progressive muscle weakness clumsiness and waddling gait skeletal deformity mental retardation frequent respiratory infections and heart failure death in 20s or earlier |
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Term
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Definition
| The fenn effect states that the greater the amount of work done by a muscle, the greater the amount of ATP cleaved |
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Term
| What causes rigor mortis? |
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Definition
Rigor mortis results from ATP depletion in muscle cells At 12 hours peak rigidity occurs due to: -inability of the dying cells to remove calcium -calcium influx into muscle cells prompotes binding of myosin cross bridges -no ATP avalable to bind myosin for cross bridge detachment -actin and myosin become irreversibly cross-linked and crossbridges remain contracted |
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Term
| What releases tension of rigor mortis and when does this occur? |
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Definition
| Within a day (48-60 hours) muscle proteins are destroyed by local enzymes released as cells degenerate causing muscles to relax |
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Term
What are the two types of muscle contraction? Describe. |
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Definition
Isometric: muscle develops tension but is not allowed to shorten, (has active, passive, and total tension) Isotonic: a contraction in which the muscle shortens while pulling a constant load (afterload); weight of object unchanged so muscle tension remains constant |
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Term
What is active tension proportional to? Where is active tension maximal? |
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Definition
| Active tension is proportional to the number of cross-bridges formed therefore it is maximal at the place where there is maximal overlap of thick and thin filaments |
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Term
| If a muscle fiber is stimulated rapidly so that there are numerous twitch summations this creates a _______ effect, also known as _______. This hyperstimulation will eventually result in a tension plateau known as ________, where there is a sustained contraction. |
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Definition
| If a muscle fiber is stimulated rapidly so that there are numerous twitch summations this creates a staircase effect, also known as treppe. This hyperstimulation will eventually result in a tension plateau known as tetanus, where there is a sustained contraction. |
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Term
| What is the major mechanism for adjusting strength of contraction in skeletal muscle? |
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Definition
| Adjust frequency of action potentials traveling down motor neurons to muscle fibers |
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Term
Muscle Contraction = ??? Muscle Shortening = ??? |
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Definition
Muscle contraction = cross bridge formation Muscle shortening = sliding of filaments |
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Term
| What determines fiber type in muscle fibers? |
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Definition
| Fiber type is dependent on the nerve that enervates the muscle fiber |
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Term
| The phosphocreatine pathway provides ATP for what type of exercise? |
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Definition
An immediate source of energy for quick, forceful movements Transfer of hi-energy P from creatine-P to ADP |
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Term
The glycogen pathway provides ATP for what kind of exercise and at what rate? |
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Definition
Main source when O2 NOT present Glycogen pathway works during anaerobic exercise at a rate of 2 1/2 times quicker than aerobic exercise. |
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Term
| When is aerobic metabolism - oxidative phosphorylation utilized for energy in skeletal muscle? |
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Definition
A main source of energy when O2 is present Fueled by glucose/fatty acids/amino acids from food |
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Term
For what period of time do the following systems operate in muscles for energy and how many moles of ATP/min do they produce? Phosphagen system Glycogen-lactic acid system Aerobic system |
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Definition
Phosphagen system: 8-10 seconds, 4 moles of ATP/min Glycogen-lactic acid system: 1.3-1.6 minutes, 2.5 moles of ATP/min Aerobic system: unlimited time, 1 mole of ATP/min |
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