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Muscles 3
Term | Definition |
---|---|
ATP | Energy molecule needed for both muscle contraction and relaxation; moves and detaches cross bridges, pumps calcium back into SR, and pumps Na and K ions back to their original positions after excitation-relaxation coupling. Depleted in 4-6 seconds. |
Glucose and Fatty acid | The organic energy sources for ATP synthesis |
Aerobic respiration | Produces far more ATP and does not generate lactate, but requires a continual supply of oxygen. Fuel includes glycose from glycogen, then bloodborne glucose, then free fatty acids. |
Anaerobic pathway | Glycolysis and Lactic Acid formation. Enables production of ATP without oxygen, but yields little ATP and lactate. |
Short-duration, high-intensity exercise (6 seconds) | ATP stored in the muscles are used first |
Short-duration, high intensity exercise (10 seconds) | ATP is formed from creatine phosphate and ADP (direct phosphorylation) |
Short-duration, high intensity exercise (30-40 seconds) | Glycogen in the muscles is broken down to glucose, which is oxidized to generate ATP--anaerobic pathway |
Prolonged-duration exercise | ATP is generated by breakdown of several nutrient energy fuels by aerobic pathway |
Phosphagen system | The combination of ATP and CP which provides all energy for short bursts (~6 seconds) of activity |
Myokinase | Transfers Pi from from ADP to another ADP, making ATP |
Creatine Kinase | Obtains Pi from phosphate storage to ADP, making ATP |
Anaerobic (lactate) threshold | Point at which lactate becomes detectable in the blood |
Glycogen-lactate system | The pathway from glycogen to lactate, produces enough ATP for 30-40 seconds of maximum activity |
Excess postexercise oxygen consumption (EPOC) | The difference between the resting rate of oxygen consumption and the elevated rate following exercise (11 L debt); needed to replace reserves, replenish the phosphagen system, serve the elevated metabolic rate, and oxidize lactic acid |
Aerobic endurance | Length of time muscle contracts using aerobic pathways; often used in light-to-moderate activity, which can continue for hours |
Anaerobic threshold | Point at which the muscle metabolism converts to anaerobic pathway |
Muscle fatigue | The physiological inability to contract despite continued stimulation, usually occurring when there are ionic imbalances. Lack of ATP is rarely a reason for fatigue unless muscles have been severely stressed |
High-intensity exercise fatigue | Thought to result from potassium accumulation in T tubules and excess ADP and Pi (which slows cross-bridge movements, inhibits calcium release, and decrease force production in myofibrils) |
Low-intensity exercise fatigue | Thought to result from fuel depletion, electrolyte loss, and central fatigue when less motor signals are issued from the brain |
Endurance | The ability to maintain high-intensity exercise for more than 4 to 5 minutes. Determined in large part by one's maximum oxygen uptake. |
Maximum oxygen uptake (VO2 Max) | The point at which the rate of oxygen consumption reaches a plateau and does not increase further with an added workload |
Oral creatine | Drug that increases level of creatine phosphate in muscle tissue, increasing speed of ATP regeneration. Useful in burst-type exercises, but may lead to muscle cramping and kidney disease |
Carbohydrate loading | Dietary regimen that packs extra glycogen into muscle cells, giving more energy, but adding a sense of heaviness |
Slow-Twitch fibers | Slow Oxidative, red, Type I; well adapted for endurance, carrying lots of mitochondria, capillaries, and myoglobin. Relatively thin and grouped in small units for precise movements, they are important for muscles that maintain posture. |
Fast-Twitch fibers | Fast Glycolytic, white, Type II; adapted for quick responses, carrying myosin with fast ATPase and a large SR that acts fast. Fibers are thick and are grouped in large units, they are important for quick and powerful movements |
Fast-Twitch intermediate | Type IIA; fast twitch fibers that are fatigue resistant. Found in other animals, but rare in humans. |
Resistance training (weightlifting) | Contraction of a muscle against a load that resists movement; stimulates muscle growth and muscles grow thicker |
Endurance training (aerobic exercise) | Improves fatigue-resistant muscles, skeletal strength, red blood cell count, and the respiratory and nervous systems. Slow twitch fibers produce more mitochondria, glycogen, and acquire a greater density of blood capillaries |
Cardiac muscle | Short and thick striated muscle that contains intercalated discs; attached to neighbors by gap junctions, reparable by fibrosis, is autorhythmic, and uses aerobic respiration. |
Smooth muscle | Nonstriated muscle that lacks T tubules; calcium instead drawn from ECF. Lacks nerve supply, but is able to undergo mitosis. Has a fusiform shape with one nucleus, and contains dense bodies instead of Z discs. |
Peristalsis | Waves of contraction brought about by food distending the esophagus or feces distending the colon |
Stress-relaxation response | When stretched, tissue briefly contracts then relaxes; helps prevent emptying while gradually filling |