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muscles study guide.doc

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ENGL 1010
Laura Sterrett

• Muscle fibers- only in skeletal/smooth muscles • Excitability- ability to receive and respond to a stimulus • Elasticity- ability to recoil and resume length after stretch • Excitability, elasticity, contractility, extensibility • Skeletal muscle is 40% of body mass • Fascicles- groups of endomysium-wrapped muscle fibers • Perimysium- fibrous connective tissue surrounding each fascicle • Epimysium- connective outer layer of muscle • Indirect attachments- tissue wrappings extend as tendons/aponeurosis • Myoglobin- red pigment storing oxygen in sarcoplasm • Myofibril- contractile elements of muscle cells • Sarcomere- region between two Z discs, smallest contractile unit • Endomysium, perimysium, epimysium • Troponin- TnI binds to actin to inhibit contraction, TnT positions tropomyosin on actin, TnC binds calcium atoms • SR stores and releases calcium when stimulated • Sliding filament theory- thin and thick filaments slide past one another to contract • Motor end plate- high surface area due to folding, location of Ach receptors • Acetylcholinesterase- breaks Ach into acetyl acid and choline, stops stimulation • Excitation-contraction coupling (EC)- action potential makes myofilaments slide • Calcium is removed by active transport after action potential ends • Wave summation- two identical stimuli delivered at high frequency builds response • Recruitment- motor unit summation • ATP regenerated by ADP and creatine phosphate interaction, anaerobic glycolysis of stored glycogen, or aerobic respiration • Anaerobic glycolysis- produces lactic acid • Slow red oxidative fiber- contracts slowly, oxygen dependent, high mitochondria, fatigue resistant • Fast glycolytic fiber- anaerobic glycolysis, white, tires quickly, contracts quickly, depends on glycogen • Fast oxidative fiber- intermediate, contract quickly, oxygen dependent • Calmodulin- calcium-binding protein in smooth muscle • Stress-relaxation response- muscle adapts to new contracted length and relaxes so it can retain ability to contract in smooth muscle (stomach shrinking & growing) • Preload- stretch on cardiac muscles right before contracting • Increased contractility= more blood ejected from heart = lower ESV • Afterload- pressure ventricles overcome to eject blood • Atrial reflex- increased venous return stretches atrial walls, HR up • Thyroxine- increase body heat and metabolic rate, causes sustained HR increase • tachycardia- abnormally fast heart rate due tu stressors • Bradycardia- slow heart rate • Congestive heart failure- CO too low to meet needs of tissues • Pulmonary congestion- left side of heart fails, suffocate from pulmonary edema • Peripheral congestion- right side of heart fails, blood stagnates in body organs and can’t get rid of waste/ give nutrients • Excitation-contraction coupling- action potential propagated down T tubules • Troponin binds to calcium to move tropomyosin out of the way • Myosin ATPases split ATP for detachment • Tetanus- smooth and sustained muscle contraction resulting from high frequency stimulation • Isometric- nothing moves despite contraction • Isotonic- muscle shortens/lengthens and load moves • Force of contraction affected by number/size of contracting cells, frequency of stimulation, and degree of muscle stretch • Three types of muscle fibers 1. Fast glycolytic (fatigable), 2. Slow oxidative (fatigue-resistant) 3. Intermediate fast oxidative (fatigue-resistant) • Smooth fibers- unstriated, spindle shaped, uninucleate, arranged in sheets, lack elaborate connective tissue coverings, no sarcomeres, no T tubules, underdeveloped SR, pace of contraction maybe set by pacemaker cells, can be electrically coupled by gap junctions, contracts slowly without fatigue • Calcium binds t
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