BIO 365R Lecture 15_Muscle II

BIO 365R Lecture 15_Muscle II - What would happen if there...

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Unformatted text preview: What would happen if there were no more ATP in a muscle Fber? ATP binding site ATP ATP ADP P + 1) Myosin is bound to Actin 2) Myosin binds ATP and disassociates from Actin 3) ATP is split causing myosin head to ratchet back 4) Myosin binds to Actin ADP P + P + 5) Power Stroke- phosphate is released from myosin allowing myosin head to ratchet forward 6) ADP is lost from myosin Z lines Z lines Ca ++ Ca ++ Ca ++ Ca ++ Low Ca in sarcoplasm ++ Ryanodine receptor sarcoplasmic reticulum Muscle is at rest sarcoplasm sarcoplasm ATP ADP + Pi Ca dihydropyridine receptor (DHPS) transverse tubule membrane Ca Ca ++ ++ ++ Hi Ca in sarcoplasm ++ Ca Activated dihydropyridine receptor Action potential invades transverse tubule and activates dihyropyridine receptor sarcoplasm sarcoplasm ATP ADP + Pi Ca sarcoplasm Ca (Ca binds to troponin and initiates sacromere shortening) Ca Ca ++ ++ ++ ++ ++ ++ Rigor Mortis • ATP levels fall so Ca 2+ cannot be pumped back into the SR. • Accumulation of Ca 2+ in the muscle cytoplasm permanently removes troponin/tropomyosin from actin. • Lack of ATP means that actin and myosin form cross-bridges and cannot let go. Isotonic vs isometric contraction Isotonic = equal tension, but changing length Isometric = equal length, but changing tension Summation of tension http://www.unmc.edu/physiology/Mann/pix_14/twitch_mc.gif Increase in fring rate (number oF APs) oF muscle causes increase in contraction because oF summation oF single twitches. http://csm.jmu.edu/biology/danie2jc/muscles/fg8-17b.giF Summation and Tetanus How do we regulate the amount of force generated by a movement? • The amount of Fring of the motorneuron (in¡uences the extent of contraction from a little contraction to tetanic contraction)....
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This note was uploaded on 04/12/2009 for the course BIO 51340 taught by Professor Zakon during the Spring '09 term at University of Texas.

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BIO 365R Lecture 15_Muscle II - What would happen if there...

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