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50 Cards in this Set
- Front
- Back
Muscles are the machinery used by the body to convert _____ _____ ____ ____ into ______ _____ that is used to do work.
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-high-energy phosphate bonds (ATP)
-mechanical energy |
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What is the instruments of the central nervous system (CNS) that are used to alter and interact with the environment?
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-Muscles
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How does an action potential excite muscle fibers so they contract?
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-By causing a dramatic increase in intracellular calcium
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Called Excitation-Contraction (EC) Coupling
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-Process that links depolarization of the muscle to an increase in intracellular calcium
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End Plate Potential
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-Local depolarization of the muscle fiber membrane
-Normal: 50-75 mV |
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Why is triggering action potentials by direct stimulation more difficult than that of a nerve?
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-there is a more negative resting potential and greater membrane capacitance
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The resting membrane voltage is primarily determined by ____ permeability, with a significant contribution from _____.
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-K+
-P(Cl) |
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What is the relationship between a single AP and muscle tension?
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-Because of Afterpotential and twitch
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Afterpotential (def)
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-the depolarized plateau of a muscle ( the rest of AP looks like that of a nerve)
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Twitch (def)
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-Muscle tension transient
-a peak after a brief but significant delay |
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Sarcomeres (def)
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-the fundamental contractile unit delimited by Z disks
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2 Proteins sets in Sarcomeres
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-Thick and Thin Filaments
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Thin Filaments Composition
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-Primarily Actin
-Regulatory Proteins: Troponin and Tropomysin |
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G-actin
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-globular actin molecule
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F-actin
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-globular molecules (G-actin) self assemble into the thin filaments
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The thin filaments of adjacent sarcomeres are joined together at the ___ ____.
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-Z line
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In the thin filaments, _____ polymerizes like two strings of beads that wind _____ around each other.
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-actin
-helically |
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What part of the sarcomere contains the thick filaments? What is it comprised of?
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-A band
-myosin molecules |
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Actin filaments have _____ _____ that can interact with the myosin molecule.
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-Active Sites
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How is the interaction between actin and myosin prevented in the absence of calcium?
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-Tropomysin covers active sites
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What does calcium binding to troponin trigger?
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-A series of conformational and molecular interactions that effect sarcomere and force generation.
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How does sarcomere shortening occur?
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-As the filaments "slide" past one another
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What are force and sarcomere shortening attributed to?
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-Interaction between thick filament myosin heads with thin filament actin molecules to form "Transfilament crossbridges"
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Crossbridges allow the filaments to _____ and _____ towards one another.
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-Grip
-Pull |
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What type of energy is used to drive the contraction process?
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-Energy liberated from ATP hydrolysis by enzymatic activity present on the myosin heads
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Tetrodotoxin (def)
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-a toxin that blocks Na+ channels and suppresses APs
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Is an AP required for a contractile event?
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-No
-Use of tetrodotoxin: injected into to cell=transient increases in intracellular calcium |
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_______ alone is sufficient to increase the intracellular calcium concentration to levels required for contraction
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-Depolarization
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Sarcolemma (def)
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-Cell membrane that surrounds a muscle fiber
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Muscle fibers contain ______.
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-Myofibrils
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What make up an myofibril?
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-Composed of the individual contractile filaments
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Sarcoplasmic Reticulum (def)
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-A bag-like structure that encircles a myofibril
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T-tubule System (def)
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-Surround the myofibril
-Narrow invaginations of the sarcolemma that run deep inside the muscle fiber to form an elaborate plasma membrane network -Brings T-tubules in close proximity to a pair of adjacent terminal cisternae of the sarcoplasmic reticulum |
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Triad (def)
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-2 Adjacent terminal cisternae of the Sarcoplasmic reticulum
-T-tubule |
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An elevation in cytosolic ______ level triggers muscle contraction.
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-Calcium
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Resting cytosolic calcium concentration measurements is ______ and during contraction it may increase ______ to ______.
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-.1uM
-20-fold -2 uM |
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____ serves as a reservoir for calcium and that APs in the sarcolemma act to trigger the release of this store calcium.
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-Sarcoplasmic Reticulum
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What do T-tubules provide for the muscle fiber?
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-A communication from the outside to the deep interior of the muscle fiber
-Provides synchronization of calcium release from SR stores, synchronized sarcomere shortening and contraction |
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T-tubule membranes possess the necessary ____ and ____ channels for AP propagation
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-Na+
-K+ |
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The T-tubules contain a high density of ______ ____ ____ ______.
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-Voltage-Gated calcium channels
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Voltage-Gated Calcium Channels (T-Tubules)
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-Act as a receptor for derivatives of 1,4-dihydropuridines
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1,4-dihydropuridines
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-Clinical agents used to treat both hypertension and angina pectoris
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Calcium channels in t-tubules are also referred to as _______ ____.
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-Dihydropyridine receptors (DHPRs)
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Why are SR calcium release channels also called ryanodine receptors?
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-The plaint alkaloid ryanodine binds to them with high affinity and locks them in the open condition
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2 Groups of Muscles
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1. Striated
2. Smooth |
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2 Types of Striated Muscles
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1. Skeletal
2. Cardiac |
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Types of Smooth Muscle
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-Vascular and Gastrointestinal
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Does skeletal muscle require calcium for contraction?
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-No
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Calcium channels are _____ _____ for skeletal muscle.
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-Voltage sensors
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Voltage-Gated Calcium release mechanism (VGCR)
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-the calcium channels present in the T-tubules "sense" the change in membrane voltage during an action potential
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