Term
| Characteristics of Actin filaments |
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Definition
1. double stranded helix of F-actin protein
2. F-actin protein made of polymerized G-actin molecules |
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Term
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Definition
| cover myosin binding sites of actin; preventing their interaction |
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Term
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Definition
| -three subunits with TnI (inhibitory); TnC (Calcium binding); TnT (Tm binding) |
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Term
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Definition
| -space between axon and muscle |
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Term
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Definition
| trough where the nerve terminal sits at the site of innervation |
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Term
| Steps in Muscle Activation |
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Definition
1. action potention reaches neuromuscular junction and releases acetylcholine
2. Acetylcholine bind to sarcolemma
3. Membrane becomes permeable to sodium ions (resulting in membrane depolarization) |
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Term
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Definition
| acetylcholine receptors on the sarcolemma are blocked by antibodies (autoimmune response); muscle cell cannot respond to nerve impulse |
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Term
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Definition
| network of tubules arising as invaginations of the sarcolemma and surrounds the A-I interfaceof each sarcomere |
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Term
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Definition
| tubules associate with terminal cisternae (expanded regions of the SR) |
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Term
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Definition
| depolarization signal transmits to SR and causes the release of stored calcium |
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Term
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Definition
| released from SR combine with TnC changing conformation of troponin complex and moves tropmyosin molecules further into grooves between actin filaments; making active sites of actin available for myosin |
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Term
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Definition
| 1. ATP binds and is cleaved by ATPase; 2. actin site exposed and myosin binds and this causing power stroke (energy stored in ATP cleavage); 3. ADP and Pi released allowing for ATP to bind and myosin releases from actin |
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Term
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Definition
| sliding of thick and thin filaments caused by myosin bridges with action molecules pulling the thin filaments toward the center of the sarcomere |
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Term
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Definition
| sensors that keep the CNS informed of the state of contraction and position of voluntary muscle (ex by Marino in class) |
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Term
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Definition
| modified muscles fibers that comprise the neuromuscular spindle |
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Term
| 2 types of intrafusal fibers |
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Definition
| 1. nuclear bag fibers (nuclei accumulated in midregion); 2. Nuclear chain fibers (nuclei arranged in circular chain); nuclear bag fibers extend beyond CT and are attached to extrafusal fibers |
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Term
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Definition
| stem cells found between the plasma membrane and the basal lamina of muscle fibers-differentiate to form myotubes |
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Term
| characteristics of cardiac muscle |
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Definition
| 1. highly branched; 2. striated; 3. nuclei centrally located with 1-2 per cell |
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Term
| characteristics of cardiac muscle |
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Definition
| 1. highly branched; 2. striated; 3. nuclei centrally located with 1-2 per cell |
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Term
| control of cardiac muscle contraction |
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Definition
| not controlled solely by neural innervation but initiated by group of cells in SA node-cells are electrochemically coupled |
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Term
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Definition
| attach muscles to each other and are complex interdigitations found at adjacent cell surfaces |
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Term
| three types of junctions of IDs |
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Definition
| 1. gap-junction-electrically couples cells together; 2. fascia adherent-anchoring sites for actin filaments to couple forces of cells; 3. desmosomes-additional junctions to hold cells together |
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Term
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Definition
| found in cardiac muscle consisting of one T tubule and one SR cisternae found at the Z line |
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Term
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Definition
| very large cell with abundant sarcoplasm and marginally located myofibrils causing coordination and automaticity to heart beat |
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Term
| location of smooth muscle |
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Definition
| respiratory tract, GI tract, and genitourinary tracts |
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Term
| smooth muscle characteristics |
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Definition
| elongated cells, centrally located nucleus, lack striations, enclosed in basal lamina and reticular fibers |
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Term
| smooth muscle stimulation |
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Definition
| may be stimulated by hormones, peptide secretions |
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Term
| contraction of smooth muscles |
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Definition
| myosin head (MLightChain) becomes phosphorylated; myosin light chain kinase; increase in calcium causes it to complex with calmodulin which activates MLC kinase causing conformational change in myosin head |
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Term
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Definition
| smooth muscle cells retain ability to proliferate and repair is possible |
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Term
| contents of sarcoplasmic reticulum |
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Definition
| calcium to initate the contractile process |
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Term
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Definition
| protein that holds together the thick filaments at the M line |
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Term
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Definition
| neurons that activate skeletal muscle |
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Term
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Definition
| alpha-motorneuron with all the muscle fibers it innervates |
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Term
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Definition
| acts as a voltage sensor in the T-tubule; coupled to the ryanodine receptor of SR by protein which blocks calcium release channel (when polarized) |
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Term
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Definition
| depolarization of T-tubule causes coupled protein to move towards DHP receptor unblocking the calcium release channel within ryanodine receptor |
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Term
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Definition
| total length of the muscle does not change |
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Term
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Definition
| initial length of the muscle prior to contraction |
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Term
| factors controlling force of isometric contraction |
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Definition
| 1. preload (overlap between thin and thick filaments); 2. number of muscle fibers activated; 3. frequency of action potentials generated by the muscle |
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Term
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Definition
| the muscle develops force and shortens |
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Term
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Definition
| load lifted by the muscle when shortened |
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Term
| phases of isotonic contraction |
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Definition
| 1. muscle contracts isometrically until force equals afterload; 2. shortens isotonically at constant velocity until shortens as much as possible; 3. contracts isometrically until it relaxs |
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Term
| velocity in isotonic contraction |
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Definition
| iversely proportional to the force of the afterload (same as the amount of shortening) |
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Term
| length of maximal mysosin cross-bridges |
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Definition
| between 2.0 and 2.2 microns |
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Term
| length-tension relationship |
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Definition
| relationship between preload and force of contraction; from 2.2 to 3.5 cross bridges decrease and force decreases; 2.0 to 1.5 and thin filaments interfere with each other decreasing force of contraction |
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Term
| effect of short resting lengths |
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Definition
| decreases amount of calcium that binds to troponin |
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Term
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Definition
| contractile force produced by a single action potential |
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Term
| summation of action potentials |
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Definition
| successive action potentials can do this because duration of a twitch is longer duration than an action potential |
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Term
| summation of action potentials |
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Definition
| successive action potentials can do this because duration of a twitch is longer duration than an action potential |
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Term
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Definition
| occurs when frequency of action potentials is high enough to prevent any relaxation of contraction between action potentials and the force |
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Term
| removal of calcium in summation of muscle |
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Definition
| if second action potential is initiated before all calcium is removed from myoplasm, then cross bridge cycling continues for longer time and force of contraction increases |
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Term
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Definition
| produces the increased force by summation; connect contractile proteins to bone and stretches during contraction |
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Term
| how SEC increases force of contraction |
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Definition
| the greater the stretch of SEC the greater force transferred to bone (like rubber band); stimulating the muscle before muscle relaxes produces greater stretch of SEC and greater force |
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Term
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Definition
| greater the afterload the greater number of mysosin molecules that must be bound to actin; greater myosin cross bridges involved slower the velocity of shortening |
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Term
| effects of increasing the afterload |
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Definition
| 1. increases latency between activation of muscle and shortening; 2. increases force produced by muscle during shortening; 3. decreases velocity; 4. decreases amount of shortening |
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Term
| load-velocity relationship |
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Definition
| velocity of afterload depends on the preload; max velocity occurs at zero afteload and is independent of preload |
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Term
| length tension relationship |
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Definition
| 1. at beginning of isotonic contraction max force of muscle is greater than the afterload; 2. as muscle shortens, max force it can produce varies; 3. muscle continues to shorten until max force equals afterload; 4. greater the afterload, the less the muscle can shorten |
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