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94 Cards in this Set
- Front
- Back
- 3rd side (hint)
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what is the ultimate source of energy required by active skeletal muscles?
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mitochondrial activity
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what is glycolysis?
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the anaerobic breakdown of glucose to pyruvate in the cytoplasm of a cell. it provides a net gain of 2 ATP molecules and generates 2 pyruvate molecules from each glucose molecule
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how many pyruvate molecules are generated during glycolysis?
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2 pyruvate per glucose molecule
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what is aeroblic metabolism?
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-it produces about 95% of the ATP demands of a resting cell
-the mitochondria absorbs oxygen, phosphate ions, ADP, and organic substrates (such as pyruvate) from the surrounding cytoplasm -large amount of energy are released and used to make ATP (primarily through the electron transport chain) |
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what happens in the electron transport chain during aerobic metabolism process?
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large amounts of evergy are released and used to make ATP
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why is the process of aerobic metabolism so efficient?
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because for each molecule of pyruvate "fed" into the citric acid cycle, the cell gains 17 ATP molecules
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what is creatine phosphate (CP)?
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a high-energy compound stored by the muscle fibers
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what happens when energy demands are low and oxygen is abundant?
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-the muscle fiber absorbs nutrients from the interstitial fluid
-builds up its energy reserves -stores a small amount of CP |
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why do muscle fibers only store a small amount of energy in high-energy compounds?
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because most energy is stored as glycogen which enables muscle contractions to continue for extended periods
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In a resting skeletal muscle why are the demands for ATP low and what happens to the surplus of ATP?
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because more than enough oxygen is available for the mitochondria to meet that demand. the extra ATP is used to build up reserves of CP and glycogen
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what do resting skeletal muscle fibers absorb? what happens once these substances are absorbed?
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they absorb fatty acids and glucose delivered by the bloodstream
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the fibers break the fatty acids down in the mitocondria and the ATP that is generated is used to convert creatine to creatine phosphate and glucose to glycogen
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what does the ATP generated by the breakdown of fatty acids in the mitochondria of a resting skeletal fiber do?
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converts creatine to creatine phosphate and glucose to glycogen
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what happens to the skeletal muscle when there is a moderate level of activity?
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-ATP demand increases which is met by the mitochondria
-the rate of oxygen consumption increase |
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what does the skeletal muscle rely on to generate ATP and provide pyruvate?
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the fiber relies primarily on the aerobic metabolism of pyruvate to generate ATP
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the pyruvate is provided by glycolysis, using glucose obtained from stored glycogen reserves
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what type of fatigue affects the muscles of endurance athletes (marathon runners) after hours of exertion?
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glycogen, lipid, and amino acid reserves are exhausted and the demand for ATP can no longer be met
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what happens at peak levels of activity?
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-ATP demands are enormous and mitochondrial ATP production rises to a maximum rate determined by the availability of oxygen
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How is ATP provided during peak levels?
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-mitochondrial activity provides 1/3 of ATP needed
-the remainder is produced by glycolysis |
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how does glycolysis produce ATP during peak levels?
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1. pyruvate levels rise in the sarcoplasm 2. pyruvate converts to lactic acid which decreases the pH level 4. changes in pH will alter the functional characteristics of key enzymes so the muscle can no longer contract
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why is pyruvate converted to lactic acid?
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because gycolysis produces pyruvate faster than it can be utilized by the mitochondria which raises the pyruvate levels in the sarcoplasm
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what type is muscle fatigue do sprinters experience?
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when the pyruvate is converted to lactic acid the intracellular and extracellular pH levels decrease causing and alteration in the functional characteristics of enzymes; therefore, the muscle fiber cant continue to contract
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what does it mean when a skeletal muscle is said to be fatigued?
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it can no longer continue to perform at the required level of activity
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why is the decline in pH within the muscle fiber during peak activity the major factor in promoting muscle fatigue?
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because it decreases calcium ion binding to troponin and altering enzyme activities
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why isnt glycolysis the most efficient way to generate ATP? (2 reasons)
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1. it uses the glucose reserves
2. it is potentially dangerous because of the dissociation of lactic acid can lower the pH of the blood and tissues |
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at what rate and how long can glycolysis produce ATP?
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it can produce ATP faster than aerobic metabolism but only until glycogen reserves are gone (1-2 minutes)
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what can glycolysis do to body temperatue?
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it can elevate it causing increased gland activity
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what happens once oxygen is available after being fatigued?
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the muscle enters the recovery period
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what happens during the recovery period due to the oxygen abundance?
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the lactate can be recycles by conversion back to pyruvate
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what two things can pyruvate in the recovery period be used by?
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1. mitochondria to generate ATP
2. a substrate for enzyme pathways that synthesize glucose and rebuild glycogen reserves |
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why are skeletal muscles so important in maintain body temperature?
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they provide 85% of the heat needed to maintain it
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what happens to the lactate during peak activity?
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large amounts of lactate produced during the activity diffuses out into the bloodstream which is absorbed by the liver and converted into pyruvate
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After peak activity, what happens to the lactate during the recovery period?
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after it is converted to pyruvate, 30% are broken down in the mitochondria, providing the ATP needed to convert the remaining 70% of the pyruvate into glucose. these glucose molecules are released into the circulation and used to rebuild the fibers glycogen reserves
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what is the Cori cycle?
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the shuffling of lactate to the liver and of glucose back to the muscle cells
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what is oxygen debt or excess postexercise oxygen consumption (EPOC)?
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the amount of oxygen needed to restore normal, pre-exertion conditions which is elevated during the recovery period
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where does most of the additional oxygen consumption occur in the recovery period?
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1. in the skeletal muscle fibers
2. in the liver cells |
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why is most of the additional oxygen consumption during the recover period occur in the skeletal muscle fibers and the liver cells?
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-skeletal fibers: must restore ATP, CP, and glycogen
-liver cells: generate the ATP needed to convert excess lactate to glucose |
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what are the three different types of muscle fibers?
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1. fast (fast glycolytic fibers)
2. slow (slow oxidative fibers (SO)) 3. intermediate (fast oxidative-glycolytic fibers) |
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what are fast fibers?
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-white fibers; type IIB fibers
-largest in diameter -theyre densely packed with myofibrils -few blood capillaries -few mitochondria -large glycogen reserves so a lot of intracellular glycogen -fatigue quickly -generate ATP by glycolysis |
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how large are the fast fibers diameter?
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2x as big as slow
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why do fast fibers generate the most powerful contraction?
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because the # of myofibrils are directly proportional to the amount of tension production
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why is the myoglobin content low in fast fibers?
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because there are few blood capillaries; therefore, they're low in oxygen and generate ATP by glycolysis
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why are fast fibers white fibers?
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because they have few blood capillaries so they lack oxygen and are white
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how do fast muscle fibers produce ATP?
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glycolysis
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why are the contractions strong and quick?
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the myosin ATPase of the densely packed sarcomere hydrolyzes ATP rapidly
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why do fast fibers experience fatigue quickly?
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because the contractions use ATP in massive amounts and have few mitochondria to generate ATP
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what are fast fibers adapted for?
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anaerobic movements of short duration: weight lifting
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what are slow fibers?
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-red fibers; type I
-slow twitch -smallest in diameter -least powerful -large amounts of myoglobin -extensive amount of blood capillaries -large amounts of mitochondria -generate ATP by aerobic respiration resistant to fatigue |
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how large is the diameter of slow fibers?
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1/3-1/2 the size of fast fiber so they have the least power and weakest contraction
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why are the skeletal muscles dominated by slow fibers dark red?
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because of the capillary supply and high myoglobin concentration
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why are slow fibers red fibers?
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because the extensive network of capillaries delivers the myoglobin which is the red carrying pigment in blood
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why are there large amounts of mitochondria?
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because there is a high oxygen supply to support it due to blood capillaries
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how do slow fibers generate ATP?
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aerobic cellular respiration (oxidative fibers)
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why is the contraction for slow fibers slower paced?
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because the myosin ATPase hydrolyzes ATP slowly so it is longer to reach peak tension
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why are flow fibers resistant to fatigue?
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theyre prolonged sustained contractions and involve aerobic endurance activities
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what substrates are used for ATP generation during contraction in each muscle fiber?
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slow- amino acids, lipids, and carbs
intermediate- mainly carbs fast- carbs |
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what are intermediate fibers?
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-type IIA
-intermediate in diameter -intermediate/low amounts of myoglobin -more extensive blood capillaries than fast fibers -higher levels of intracelluar glycogen (glycogen reserves) than slow fibers -more resistant to fatigue than fast fibers |
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why do intermediate fibers more closely resemble fast fibers?
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because they're pale and have an intermediate/low concentration of myoglobin
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how do intermediate fibers generate ATP?
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both aerobic cellular respiration (oxidative) and anaerobic glycolysis
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why are intermediate fibers more resistant to fatigue than fast?
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because they use both aerobic and anaerobic processes
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why is the speed of contraction for intermediate fibers faster than SO fibers?
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the myosin ATPase hydrolyzes ATP 3-5x's faster
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what type of activities do intermediate fibers support?
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walking and sprinting
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how many fiber types does one motor unit involve?
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one motor unit only involve one fiber type
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where are no flow fibers in the body?
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eye or hand
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what are back and calf muscles dominated by?
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slow fibers to maintain an upright posture
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what determines the percentage of fast vs slow fibers in each muscle? intermediate?
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-fast vs slow: genetics
-intermediate: athletic training |
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what is hypertrophy?
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the enlargement of the stimulated muscle
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what three things do muscle fibers develop as a result of repeated, exhaustive stimulation that leads to hypertrophy?
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1. more mitochondria
2. higher concentration of glycolytic enzymes 3. larger glycogen reserves |
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what happens to the muscle during hypertrophy?
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-the fibers have many myofibrils so the muscle becomes stronger since tension production is large
-the muscle enlarges as a whole because each fiber increases in diameter |
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what is atrophy?
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the reduction is muscle size, tone, and power; occurs when a skeletal muscle is not regularly stimulated and loses tone and mass
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why is physical therapy crucial for people who are temporarily unable to move normally?
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because dying muscle fibers cannot be replaced and in extreme atrophy the functional losses are permanent
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why can disorders that affect the nervous system indirectly affect the muscular system?
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because skeletal muscles depend on motor neurons for stimulation
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what is polio?
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when a virus attacks motor neurons in the spinal cord and brain, causing muscular atrophy and paralysis
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what is paralysis?
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loss of voluntary movement
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what is tetanus?
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-body releases powerful toxin that inhibits motor neuron activity
-sustained, powerful contraction of skeletal muscles throughout body |
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what is botulism?
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-caused by consumption of food contaminated with toxins
-produces paralysis of skeletal muscles by preventing ACh release at neuromuscular junctions |
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what is myasthenia gravis?
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the loss of ACh receptors at the neuromuscular junctions and results in muscular weakness
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what happens when skeletal muscles start to deteriorate because they are deprived of nutrients and oxygen for an extended period of time?
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1. the fibers run out of ATP and the sarcoplasmic reticulum is unable to pump Ca2+ out of the sarcoplasm
2. the Ca2+ ions diffusing into the sarcoplasm form extracellular fluid then trigger a sustained contraction. without ATP, the cross bridges cannot detach from the active sites so the affected muscle fibers lock up |
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what happens when there in no ATP if a sustained contraction is triggered?
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the cross bridges cannot detach from the active sites so the affected muscle fibers lock up
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what is rigor moris?
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a generalized skeletal muscle contraction that occurs shortly after death, throughout the whole body, beginning with the smaller muscles of the face, neck, and arms
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what causes rigor moris to occur?
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the SR deteriorates, calcium ions are releases, and a sustained contraction begins. ATP reserves are exhasted and the muscles become locked
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what does rigor moris begin and end?
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begins: 2-7 hours after death
ends: 1-6 days but the timing depends on environmental factors (temp) |
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what are three reasons for ATP/E?
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1. myosin cross-bridge requires ATP
2. to transport Ca2+ back to SR 3. Na+/K+ ATPase pump |
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what are three ways to produce ATP?
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1. creatine phosphate
2. anaerobic cellular respiration 3. aerobic cellular respiration |
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what is creatine phosphate also called and what does it do?
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-phosphogen system
-the cell uses the PO3- stored on creatine to phosphorylate the ADP and AMP within the sarcoplasm -stores 3-6 x's more energy than ATP in relaxed muscle -provides addition 8-10 seconds- very fast |
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where does glycolysis take place in anaerobic respiration and what does it provide timewise?
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-within the sarcoplasm
-1.3-1.6 minutes |
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what four things does normal muscle function require?
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1. lots of intracellular reserves
2. normal blood oxygen levels 3. blood pH optimum 4. normal circulation |
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if a muscle is fatigued and a stimulation occurs, what happens?
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the muscle still wont contract
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what are the two main causes of muscle fatigue?
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1. depletion of metabolic reserves: ATP, CP, glycogen (glucose), lipids, amino acids
2. decrease in pH |
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what is central fatigue?
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mental fatigue in response to pain due to decrease in pH
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what are the four steps involved in recovery?
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1. lactic acid removal
2. oxygen debt 3. recovery of muscle glycogen 4. heat production |
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what are the three steps in the Cori cycle which facilitate lactic acid removal?
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1. LA travels from blood to liver
2. liver converts it into pyruvic acid, then to glucose 3. glucose is released and travels to the muscles |
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what happens in the recovery of muscle glycogen?
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-food replenish and store glucose
-differences in diet |
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what happens in heat production during recovery?
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-30% of energy released is converted to useful work --> ATP capture
-70% lost as heat -homeostatic mechanisms (sweating) prevent dangerous levels |
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what happens when an oxygen debt occurs?
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1. low pH stimulates respiratory centers
2. high respiratory rate and depth 3. generation of ATP for cori cycle 4. in muscles it refills myoglobin, stores creatine (PO3-) and ATP |
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how can differences in diet effect the recovery period?
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high CHO - up to 2 days
high fat/high protein- atleast 5 days |
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