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37 Cards in this Set
- Front
- Back
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What is the significance and principal of the length-tension relationship in skeletal muscle? |
Amount of tension generated depends on length of muscle before it was stimulated. Depends on how streched it is |
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What is a twitch contraction?
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A single brief stimulus at the threshold voltage that produces a quick cycle of contraction and relaxation |
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What is the effect of an increased stimulus frequency on twitch contractions?
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Increased stimulus frequency (closer stimuli) produce stronger twitches |
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What is the effect of stimulating muscle with higher and higher voltages?
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Produces stronger contractions |
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What is the effect of stimulating muscle with higher and higher frequencies of voltage?
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Higher frequency stimulation (20-40 stimuli/second) generates gradually more strength of contraction |
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What is tetanus in muscle contraction?
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When the twitches fuse into a smooth, prolonged contraction because of increased frequency of stimulation Tetanus means muscle tone |
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How are isometric, concentric, and eccentric muscle contractions different?
Which of the previous contraction are isotonic? |
Isometric: develops tension without changing length Concentric: same tension while shortening (isotonic) Eccentric: same tension while lengthening (isotonic) |
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What are the sources of ATP for muscle contraction during the first few seconds through 10 seconds of muscle contraction?
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Aerobic Respiration: using oxygen from myoglobin Phosphagen System: small amount of ready to go ATP, but not much storage of ATP so only lasts 10 seconds |
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What is the Glycogen-lactic acid system and what is the phosphagen system?
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Glycogen-Lactic Acid System: (Anaerobic Fermentation) – ATP production is limited and only lactic acid is produced. This system takes over after phosphagen system is depleted. Net gain of ATP from Glucose Phosphagen System: supplies most ATP for brief exercise or short bursts |
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What are the enzymes used in the phosphagen system?
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Creatin kinase- transfers phosphate group from phosphate storage molecule creatine phosphate to make ATP Myokinase transfers phosphate group from one ADP to another forming ATP |
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How are long term energy needs provided for in muscle?
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Aerobic respiration: Needed for prolonged exercise – produces 36 ATP/glucose molecule - Limits set by depletion of glycogen, blood glucose levels, loss of fluid and electrolytes |
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What is exercise post oxygen consumption via heavy breathing used for?
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Replacement of oxygen reserves in myoglobin, hemoglobin, lungs, plasma Replenishes the phosphagen system by synthesizing ATP and using some to donate Pi back to creatine Oxidizing lactic acid to pyruvate Serving the elevated metabolic rate that occurs as long as the body temperature remains elevated by exercise |
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Compare and contrast the differences between slow and fast twitch muscle.
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Slow twitch- Type I- slow oxidative, slow twitch fibers, deep red, smaller, abundant myoglobin, capillaries, abundant mitochondria for aerobic respiration, high endurance and resist fatigue ex: soleus, postural muscles of the back Fast twitch- Type IIB- fast glycolytic, fast twitch fibers, white, rich in enzymes for phosphagen and lactic acid system, fatigue more readily, larger, fewer mitochondria , ex: extraocular eye muscles, gastrocnemius, and biceps brachii - All fibers of a motor unit belong to the same type - All muscles composed of both but the proportions are different |
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What is VO2 max?
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- The point at which the rate of oxygen consumption reaches a plateau and does not increase further with added work load - larger in trained athletes |
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What are the processes that lead to muscle fatigue?
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- Decline of ATP synthesis as glycogen is consumed - No ATP= inability for Na+/K+ pump to maintain membrane potential - Lactic acid causes lower pH à inhibits enzyme function for contraction - Accumulation of K+ in ECMà hyperpolarization - Motor fibers use up the Acetylcholine à junctional fatiguex |
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What are the factors that determine the strength of muscle contraction?
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- Muscle size - Length –tension relationship (at resting length can produce more force than one that shortened or stretching) - Size of motor units - Multiple motor unit summation- more motor units = more efficiency - Temporal summation- nerve impulses come at increased frequency |
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What changes take place in skeletal muscle during resistance training verses endurance training?
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- Endurance training- (aerobic exercise) - slow twitch fiber, increase of mitochondris, glycogen, and density of capillaries - Resistance training- (weight lifting) -stimulates cell enlargement due to synthesis of more myofilaments |
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Compare characteristics of cardiac muscle (stimulus for contraction, type of innervation, length of contraction, energy source, mitochondria number and size, vulnerability to oxygen deficit) with that of skeletal muscle.
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Cardiac muscle: - thick cell shaped, branched - multinucleated but not as much as skeletal muscle - intercalated discs (gap junctions and mechanical junctions) - sarcoplasmic reticulum is less developed in cardiac muscle than skeletal - damaged cells fibrose they don’t regenerate by mitosis like skeletal muscle - autorhythmic because of pacemaker cells - maintains tension /no quick twitches like skeletal muscle - uses aerobic respiration almost exclusively, large mitochondria (25% compared to 2% in skeletal muscle) - calcium comes from extracellular and sarcoplasmic reticulum Involuntary |
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What occurs during a myocardial infarct? What can be measured in the blood to detect this?
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Death of cardiac muscle due to ischemia (lack of blood) Troponin is measured to detct this |
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What are some characteristics of smooth muscle?
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- Fusiform cells with one nucleus - No striations, sarcomeres, T tubules, or Z discs - Calcium for contraction comes from extracellular fluid, not sarcoplasmic reticulum - Single (large number of cells contract as a unti) and multi unit (each motor unit contracts independent of the other motor units) - Capable of mitosis and hyperplasia - No troponin, calmodulin is the Ca+2 binding protein |
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What are dense bodies in smooth muscle?
From where does the predominant source of calcium required for smooth muscle contraction come? |
- Calcium comes from extracellular matrix - Dense bodies are what the thin filaments attach to instead of the sarcolemma |
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Describe multiunit smooth muscle. Where is it typically found?
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- Each motor unit contracts independent of the other unit - Largest arteries, iris, pulmonary air passages, arrector pili muscle of hair |
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Describe single-unit smooth muscle. Where is it typically found?
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- More widespread - Visceral smooth muscle - Electrically coupled by gap junctions - Large number of cells contract as a unit - Gut and arteries |
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Which type of smooth muscle uses gap junctions and which uses nerve terminals on individual muscle cells?
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Single unit- uses gap junctions Multiunit- uses nerve terminals on individual muscle cells |
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What is the calcium binding protein in smooth muscle?
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Calmodulin of the thick filament (not troponin of thin filament) |
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What is the major intermediate filament protein in all smooth muscle cells?
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- Desmin is in all smooth muscle cells - Vimentin is in vascular smooth muscle cells |
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Describe the various methods by which calcium channels can be triggered to open in smooth muscle?
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- Calcium channels are triggered to open by voltage, hormones, ligand gated channels, neurotransmitters, or cell stretching. |
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Are there smooth muscle pacemaker cells in certain organs?
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Yes, in GI tract are autorhythmic creating perastalsis |
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Compare the efficiency of ATP usage between smooth muscle and skeletal muscle. Compare contraction and relaxation rate.
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1) Calcium binds to calmodulinà activates light-chain myokinase 2) Myokinase transfers Pi from ATP to head of myosinà activates myosin ATPase 3) Myosin binds to actin 4) Power stroke occurs when ATP is hydrolyzed Contraction and relation is much slower in smooth muscle because of slow myosin ATPase and slow pumps that remove Ca+2 Smooth muscle uses less ATP to maintain same tension- latch bridge mechanism |
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How does stretch affect and organ that contains smooth muscle in its walls?
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Stretch opens mechanically gates calcium channels causing muscle response |
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Contracture
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abnormal muscle shortening caused by failure of Ca+2 pump to remove Ca+2 from sarcoplasm back into the SR |
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Cramps
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muscle spasm triggered by heavy exercise, extreme cold, dehydration, lack of blood flow |
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Crush syndrome
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shock-like state after massive crushing of muscle, can cause fatal fever, cardiac irregularities, and kidney failure |
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Delayed onset muscle soreness
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pain, stiffness, or tenderness felt after strenuous exercise because of microtrauma to muscles, disrupted Z discs, elevated levels of myoglobin , creatine kinase, and lactate |
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Disuse atrophy
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reduction in muscle fiber size because of erve damage or decreased use |
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Fibromyalgia
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chronic muscular pain and tenderness, caused by infectious diseases, physical and emotional trauma, or medications |
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Myositis |
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