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46 Cards in this Set
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Skeletal Muscle Connective Tissues |
Epimysium Fasciculus Perimysium Endomysium Sarcolemma (Cell Membrane) |
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Define: Epimysium |
Connective tissue surrounding entire structure |
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Define: Fasciculus |
A bundle of muscle fibers (up to 150) |
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Define: Perimysium |
Connective tissue surrounding individual muscle fibers |
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Define: Endomysium |
Connective tissue surrounding individual muscle fibers |
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Define: Sarcolemma |
The cell (plasma) membrane surrounding the muscle fiber |
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Identify the Characteristics of Tendons |
(1) comprised of tough "non-living" fibers which are metabolically inactive compared to muscle and bear tremendous forces during muscle contraction (2) Intramuscular network of connective tissues coalesces and becomes continuous with dense connective tissue of tendons (3) Tendons rigidly cemented to periosteum (outermost covering of bone) |
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Identify the Anatomy of Blood Supply to Skeletal Muscle |
(1) Arteries and veins enter muscle along with connective tissue and oriented parallel to individual muscle fibers (2) Branch repeatedly into numerous capillaries and bemuses, forming vast networks in and around endomysium |
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Capillaries in Sedentary and Trained Fibers |
Sedentary = 3-4 capillaries per fiber Trained= 5-7 capillaries per fiber |
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What Happens to Blow Flow to Muscles During Maximal Exercise? |
During maximal exercise, blood flow to muscles may increase 100 x resting level |
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Three Factors that Account for the 100 fold Increase in Muscle Blood Flow During Exercise |
(1) Alternate contraction and relaxation of muscles (mechanical) (2) Constriction of arteries and arteries to inactive areas (gut, kidney, and skin) due to the release of adrenaline and noradrenaline (epinephrine and norepinephrine)(neurohumoral) (3) Vasodilation of active muscles due to local metabolites (i.e. decrease in O2 and pH, and increase in CO2 and H+)(auto regulation)(chemical) |
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Define: Sarcomere |
Contractile unit of myofibril and the smallest functional unit of muscle containing the myofilaments myosin and actin |
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Describe: Z Line |
Thin sheet of structural proteins that divide sarcomeres from each other and the attachment site for actin and myosin and marks end of each sarcomere |
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Describe: I Band |
Light regions of the sarcomere where actin filaments are primarily located, thin filament (light area) on either side of Z line |
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Describe: A Band |
Dark portion of the sarcomere where myosin filaments are primarily located, area of thick and thin filament overlap (dark area) one per sarcomere |
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Describe: H Zone |
Center of the sarcomere, where there is a portion of the myosin filament with no overlap of the actin, thick filament only bisected by M Line which delineates sarcomere's center, disappears during contraction |
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Describe: Sarcoplasmic Reticulum |
Netlike system of tubules and vesicles and surround myofibrils and serve as storage area for calcium |
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Where is Calcium Stored and the Role of Calcium Initiating the Contractile Process? |
Calcium is stored in the outer vesicles of the SR The role of calcium in initiating the contractile process is that is is released into the sarcoplasm |
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Where does Calcium Bind? |
Calcium binds to troponin, which causes a shift in the position of tropomyosin to uncover the "active site" on the actin |
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Define: Motor Unit |
Single motor nerve and muscle fibers it supplies/intervates |
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Define: Neuromuscular Junction |
Synapse between a motor neuron and skeletal muscle |
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Identify the Two Principle Contractile Proteins Found in Skeletal Muscle |
Myosin and Actin |
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Describe the Composition of the Myofibrils |
(1) Contains contractile units called sarcomeres (2) Sarcomeres contrain myofilaments called myosin and actin (3) Each myosin is surrounded by 6 or more actin (4) Actin and myosin are the principle contractile proteins |
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Identify the Role of Acetylcholine in Activating the Muscle Contractile Process |
Acetylcholine binds with receptors on the motor endplate, producing an end-plate potential that exceeds threshold and lead to action potentials that are conducted down the transverse tubules deep into the muscle fiber |
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What is the Function of Acetylcholinesterase? |
Acetylcholinesterase degrades and breaks down the neurotransmitter acetylcholine |
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Describe the Sliding Filament Theory of Muscle Contraction |
(1) AP causes depolarization (2) Sodium in, Potassium out (3) Ca2+ is released into the sarcoplasm, then binds to troponin, which sifts and uncovers the "active sites" on the actin (4) ATP is broken down into ADP+Pi+energy, the released energy is used to "cock" myosin cross-bridge (5) The "cocked" myosin cross-bridge attaches to the active site on actin and pulls the actin molecule over the myosin (6) Attachment of "fresh" ATP to the myosin cross-bridge allows the cross-bridge to detach from actin and the contraction cycle is repeated as long as Ca2+ is present (7) When AP stop, the SR actively removes Ca2+ from the sarcoplasm and tropomyosin again moves to its inhibitory position covering the active sites on the actin molecules |
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Identify the Enzyme that Breaks Down ATP and is also Used to Determine Muscle Fiber Type |
ADP + Pi + energy, the released energy is used to "cock" myosin crossbridge |
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Define: Multiple Motor Unit Summation |
Varying number of motor units contracting at any given time |
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Define: Wave Summation |
Varying frequency of contraction at any given time |
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Define: Twitch |
Increased force generation by muscle in response to single neural impulse |
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Define: Tetanus |
Fusion of successive contractions into smooth sustained contraction |
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Characteristics of Slow Twitch Motor Units |
(1) Smallest motor neuron has lowest threshold for stimulation (2) Tend to be deep (3) Oxidative (ST or I) (4) Endurance athletes have greater percent ST fibers (5) Greater % ST = increased aerobic power (VO2MAX) |
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Characteristics of Fast Twitch Motor Units |
(1) Larger alpha motor neuron has highest threshold for stimulation (2) Tend to be superficial (3) Oxidative-Glycolytic (FTA or IIa) (4) Glycolytic (FTB ro IIx) (5) FTC (unclassified) (6) Sprint/Power athletes have greater % FT fibers (7) Founded by German Italian scientists |
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Describe Anatomy and Physiology of Muscle Spindle |
(1) Detects lengths and velocity changes in muscle (2) Consists of "intrafusal" fibers that run parallel to muscle fibers or "extrafusal" fibers (3) Contraction and length changes are coordinated between intra and extrafusal fibers via spinal cord and modulate force generated by muscle (4) Activation of spindle causes muscle contraction |
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Describe Anatomy and Physiology of Golgi Tendon Organ (GTO) |
(1) Primarily activated by contraction (2) Stretch receptors are responsive to force generated by muscle (3) Located in musculoteninous junction in series with extrafusal fibers (4) Activation of GTO causes muscle relaxation |
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Describe Neural Adaptation to Skeletal Muscle Following a Prolonged Resistance Training Program |
Neural Factors: may be responsible for strength increase in first 3-4 weeks of training, after which, hypertrophy plays a dominant role Neural Changes: (1) Increase motor unit synchronization (2) Increase firing rate of motor units (3) Decrease inhibitions (e.g. down-regulation of the GTO) |
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Describe Neural Adaptation to Biochemical Factors a Prolonged Resistance Training Program |
Biochemical Factors: (1) in PC (22-40%), ATP (18-25%) and my-kinase activity (2) Reduce aerobic function (3) Decrease in mitochondria and aerobic enzymes |
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Describe Neural Adaptation to Morphological Factors Following a Prolonged Resistance Training Program |
Morphological Factors: (1) Increase total contractile protein (2) Number and size of myofibrils (3) Connective tissue surrounding fibers (4) Bone mass and density (5) Ligament tendon size |
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Describe the Factors that Account for Muscle Hypertrophy in Humans |
(1) Total contractile protein (2) Number and size of myofibrils (3) Connective tissue surround fibers (4) Bone mass and density (5) Ligament and tendon size *Strength training produces greater hypertrophy in FT compared to ST fibers |
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Is there Good Evidence to Support Muscle Hyperplasia in Humans? |
There is limited research to support the interconversion of ST, FTIIa, FTIIx fibers and no change in number of muscle fibers due to longitudinal splitting |
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Describe the Training Adaptations to Skeletal Muscle for Men vs Women |
(1) In men, average arm and leg strength is more compared to females due to increased body size and decreased body fatness (2) Recreational men show similar relative % increase in fiber size and muscular strength compared to recreational females (3) When strength is expressed relative to LBM; leg strength is equal for males and females and arm strength is normally less for females (4) Female body builders FT fibers are similar size to male body builders |
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Describe the Training Adaptations to Skeletal Muscle for Older Adults |
(60-72 yrs.) show hypertrophy with strength training, but it may take a longer period of time compared to younger males |
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Describe the Training Adaptations to Skeletal Muscle for Children |
Research shows resistance training of prepubescent male and female children can result in significant strength gains (i.e. 52% increase in trained vs. 2% increase in untrained) |
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What Special Recommendations would you Provide for Children Involved in a Resistance Training Program? |
Heavy lifting should be limited to 8-RM (approximately 80% of 1-RM) or more (repetitions) prior to Tanner Stage 5. Maximal lifts should not be attempted prior to this phase of development |
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Possible Essay Question: Describe the Major Physiological Events that Occur in Skeletal Muscle which are theorized to cause Delayed Onset of Muscle Soreness (DOMS) |
(1) Strenuous muscle contractions result in structural damage in muscles (2) Membrane damage occurs including damage to the membranes of sarcolemma and SR (3) Calcium leaks out of the SR and collects in the mitochondria which inhibits ATP production |
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Possible Essay Question: Discuss the prevention and treatment of DOMS |
Prevention: (1) Warm up and cool down (2) Increase training intensity and volume gradually (first 5-10 training sessions) (3) Avoid eccentric contractions (i.e. no negative lifts or prolonged downhill running) Treatment: (1) Ibuprofen (NSAIDS) used with discretion (2) Reduced training intensity (3) Use static stretching on affect muscles |