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18 Cards in this Set
- Front
- Back
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What are the histological differences between skeletal, smooth, and cardiac muscles
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Cardiac Muscle are striated Cardiac muscle fibers are long cylindrical cells with one or two nuclei. The cardiac muscle fibers are joined end to end by specialized junctional regions called the intercalated discs. The intercalated discs provide anchorage for myofibrils and allow rapid spread of contractile stimuli between cells. Can generate there own action potentials Skeletal muscle are striated are under voluntary control. Contain multiple Nuclei and have fast twitch fibers and slow twitch fibers. Skeletal muscle cells are innervated by motor neurons Smooth muscle innervate all hollow organsis specialized for slow and sustained contractions of low force. Instead of having motor units, all cells within a whole smooth muscle mass contract together. Smooth muscle has inherent contractility, and the autonomic nervous system, hormones and local metabolites can influence its contraction. Since it is not under conscious control, smooth muscle is involuntary muscle. |
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Describe the functions of the specialized structures in a muscle fiber myofibrils SR sarcolema and T Tubule.
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T tubules allow for quick depolarization action potentials spread through cell membrane through T Tubule. sarcoplasmic reticulum (SR)the muscle fiber's version of smooth endoplasmic reticulum; function is to temporarily store calcium sarcolemma cell membrane of muscle fiber myofibrils bundles of very fine cytoskeletal filaments that extend lengthwise along skeletal muscle fiber and almost fill the sarcoplasm |
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Define muscle tension, load, and muscle twitch.
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Muscle tension refers to the condition in which muscles of the body remain semi-contracted for an extended period.
Muscle twitches are fine movements of a small area of muscle. |
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Describe the structure and functions of thin (actin and accessory proteins) and thick (myosin + titin) myofilaments. |
The thin filament made of actin, troponin, and tropomyosin the functions are to support muscle contraction
The thick Filament consist of myosin and their heads. |
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Describe the contraction (a.k.a. cross-bridge) cycle. What is a cross-bridge? What happens when ATP binds the myosinhead? What happens when ATP is hydrolyzed (broken into ADP and a phosphate group)? What happens when myosin releases the phosphate group leftover from ATP hydrolysis? Why are Ca2+ and and ATP neededfor the contraction cycle to occur? (Fig. 12.9; pp. 386-388)
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A cross bridge is the binding and contraction of the two filaments involved in muscle contraction The cross bridge cycle is initiated when calcium binds troponin to reveal the active sites on tropomyosin. 2 Atp BInds to The myosin head after the molecule becomes hydrolyzed myosin headscock the to initiate contact or (crossbridge) Between 2 filaments 3 Power stroke is initiated by myosin heads pulling acting towards the M-line 4 Another ATP binds to myosin resulting in myosin releasing the actin.
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What causes rigor mortis?
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Muscle are unable to relax due to no ATP being present to remove calcium from the cells. |
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Describe excitation-contraction coupling (Figure 12.10)
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ECC is the process by which actions potentials are generated in skeletal muscle. 1The neurotransmitter is ACH is released as a result of somatic motor neurons and binds to nictoninc receptors at the nueromuscular junction. 2 Ach opening allow for K and Na to cross the membrane More NA come in than K leaving Depolarizing the cell making it more positive 3 Action Potential aka sodium travels down T-tubule to alter DHP Receptor 4 The influx of sodium alters DHP Receptors and opens RYR Calicum Release channels. to allow calcium out of sarcoplasmic rectilum and end to cyto plasm. 5 this allows calicum to bind to tropin which reveals tropomision active sites so that mysoin and actin can complete the crossbridge and power stroke. 6 to end the interaction Ca atp Pase pumps pump Ca back into sarcoplasmic rectilum. 7 less calicum in cytoskelton Ca unbind from troponin which ends contraction.
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What are the three phases of a muscle twitch, and which of the above molecular events occur during each phase? (Fig.12.11)
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latent period-phase 1 of muscle twitch (2-3 msec)-action potential moves across sarcolemma, down T-tubules to SR, Ca++ released-no tension
ontraction phase-phase 2 of muscle twitch -binding of actin/myosin & powerstrokes-tension increases relaxation phase-phase 3 of muscle twitch-detachment of myosin-tension decreases |
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What is summation, fused tetanus and unfused tetanus? Could you identify these conditions on a graph of tension vs.time?
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unfused tetanus:- time between stimuli allows a very small amount of relaxation.
fused tetanus:- time between stimuli is too short to allow any relaxation.- muscle stays completely contracted. Summation is two muscle contractions that occur congruently the second contraction occurs before the first one can end |
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Understand how the three types of skeletal muscle cells (slow twitch, fast twitch oxidative, and fast twitch glycolytic fibers)are different from one another. E.g. which types have the fast myosin ATP-ase and which have the slow myosin ATP-ase?Which use aerobic respiration and which use glycolytic pathways?
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Slow-twitch fibers (Type 1)– Myosin isoform has a slow ATP-ase– Rely primarily on aerobic breakdown of glucose(oxidative phosphorylation Pumps CA SLOW longer contraction
Fast twitch OG fibers (type 2) Myosin isoform has a fast ATP-ase– Rely primarily on anaerobic breakdown of glucose– Split ATP more rapidly– Two types of fast-twitch fibers:• oxidative-glycolytic fibers use oxidative&glycolytic metabolism) PUMPS CA TO SR FAST FAST Twitch G 2X glycolytic fibers (Type 2X; rely primarily on anaerobic glycolysis) Fatigue Quicker |
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what is the relationship between sarcomere length and tension / contractile strength of a muscle fiber
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As the length of the sarcomere decrease the tension builds up the contractile strengh of a muscle fiber is related to the presence of atp which is used to create contractions |
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What is a motor unit
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group of muscle fibers that function together and the somatic motor neuron that controls them
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What is recruitment and how does it contribute to a muscle organs ability to generate different amounts of tension (to overcome loads of different size
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process by which additional motorunits (within a muscle) are activated by the nervoussystem increases contractile force of a muscle organ
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what is asynchronous recruitment |
Asynchronous recruitment of motor units helpsavoid fatigue– Different motor units take turns maintaining tension
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What is the difference between single unit smooth muscle and multi unit smooth muscle
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Multi-unit smooth muscle, ARE the smooth muscle cells in an organ all behave independently - each cell contracts and relaxes on its own. Histologically, multi-unit smooth muscle have fewer gap junctions than other types of smooth muscle. Since each smooth muscle cell is on its own, there is no great need to electrically couple the cells via a gap junction
Single-unit smooth muscle is named because all the smooth muscle cells in the organ behave as one unit. Histologically, this is accomplished by having a lot of gap junctions interconnecting the smooth muscle cells. Since gap junctions allow for electrical connections between cells, when one smooth muscle cell depolarizes, they all do. Rhythmically active smooth muscle is often also single-unit smooth muscle |
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Describe the special features of smooth muscle cells. How does smooth muscle contract without sarcomeres? What aredense bodies and how are they connected to one another? (Fig. 12
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Smooth Muscle7.
Not arranged in sarcomeres8. Contraction initiated by electrical or chemicalsignals or both 9. Controlled by the autonomic nervous system 10.Lacks specialized receptor regions 11.Ca2+ from sarcoplasmic reticulum andextracellular fluid 12.Ca2+ initiates a cascade ending withphosphorylation of myosin light chain andactivation of myosin ATPase |
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How is EC-coupling different in smooth muscle than in skeletal muscle? Where does Ca2+ come from and how does it get into the cell? How does the increase in Ca2+ allow myosin and actin to interact? What role do calmodulin and MLCK play |
smooth muscle has no tropoin or t-tublues less myosin than actin
action potential generated by CA ENTERING FROM ECF and SR CA bind to Calmodulin instead of Tropoin which activates MLCK which in turn Phosphorylates Myosin light chain in myosin heads which increases myosin ATP activity for contraction and relaxtion Enhances AtP activity ACTIVATES CROSS BRIDGE CYCLE muscle tension |
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How is relaxation different in smooth muscle than in skeletal muscle? What role does MLCP play
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Calicum sodium exchange pump and MLCP regulates by undoing the muscle contraction process |
