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Lecture 5

BIOL 2213 Lecture 5: Phys10:23

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BIOL 2213

Slide 33: After totally relaxed = no summation Before total relaxation occurs = summation If the muscle fiber is stimulated repeatedly at a rapid rate = fused tetanus (max amount of tension and stays that way) Unfused: many stimuli but doesn’t stay tense Slide 34: -How much is the sarcomere contracted -Maximally contracted: shortest possible length -Maximally extended: longest, most stretched out, very little overlap -At maximal shortness, it can’t get any shorter Intermediate overlap: where maximum amount of force is generated (can still get shorter, enough overlap to generate force) Slide 35: Muscle fibers have a lot of mitochondria to make the ATP ***Will be on the exam*** Slide 36: Creatine phopshpate: formed in liver, travels in the blood – formed when muscles are relaxed & when the muscle fibers are contracted, the creatine phosphate is used to make ATP First step in cellular respiration is glycolysis (not very efficient- 2 molecules ATP) Takes NAD and gets NADH through fermentation Glycolysis is a way that cells can make ATP when there is no oxygen and is accompanied by process of fermentation used to generate NADH Prodcut: lactic acid – builds up in the muscle cells Won’t run out of glucose – have to maintain glucose in homeostasis Won’t run out of ATP Slide 37: ATP is stored in fairly low concentrations within the muscle cells When you start the contraction, the first bit of ATP that is used just comes from the ATP in the cytoplasm Glycolysis causes build up of lactic acid Glucose is in blood and is highly regulated Can also make ATP from fatty acids (stored in fat – triglycerides) and can make ATP from breakdown products of amino acids ATP formed by: creatine phosphate, glycolysis and aerobic respiration (cellular respiration) Slide 40: Lactic acid build up makes the pH drop and will denature different proteins involved in muscle fiber contraction Slide 42: Consciously don’t feel like continuing to work out (It hurts to much so you consciously stop) Slide 43: -Not striated -Shorter than skeletal muscle fibers -No troponin: cross bridge cycle occurs different in smooth muscles -Myofilaments are not arranged into sarcomeres Slide 45: No sarcomeres = why there are no striations Slide 46: -Black lines: thin filaments (actin) -Thick filaments not arranged into sarcomeres -Dense bodies in plasma membrane -Dense bodies pull on plasma membrane and make cell get shorter (how it contracts) Slide 47: -Calcium binds to enzyme causing myosin head to be phosphorylated (how myosin head becomes activated) and can then bind to actin and go through cross bridge cycle -When cross bridge cycle is over, myosin head losing phosphate through myosin light chain phosphate and it stops Slide 49: To initiate cross bridge cycle, calcium is coming from somewhere (source can come from variety of places – outside of cell or endoplasmic reticulum) Calcium binds to CA calmodulin, which is in contact with MLCK When calcium is present, myosin is phosphoyrlated (MLCK) and that causes the cross bridge cycle to occur If the calcium goes away, the MLCK will take the phosphate off the myosin head and it stops the cross bridge cycle Endoplasmic reticulum is actually sarcoplasmic reticulum (in smooth muscle cells) Slide 50: Calcium channels that can allow calcium to come in from outside the cell When cross bridge cycle stops calcium can be pumped out Slide 51: If action potential is generated, it’s an all or none response (twitch) – always at the same magnitude – THIS IS NOT TRUE FOR SMOOTH MUSCLE -Smooth muscle contractions can be graded (vary in magnitude) -Smooth muscle can either be stimulated to contract or relax (not true in skeletal muscle – only always
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