Lecture 21 Muscle Energetics Claudia Stanescu Ph D Office hours Tuesday and Thursday 1 2pm in Gittings 108 or by appointment Extra office hours posted on D2L Objectives pp 309 311 sec 10 4 1 Describe the several substrate and or metabolic sources of ATP used to support muscle contraction and the approximate length of time each is capable of sustaining contraction 2 Compare and contrast the characteristics of glycolytic anaerobic and mitochondrial aerobic oxidative energy metabolism 3 Define fatigue and describe its most common physiological cause 4 Discuss the Cori cycle and basis of the O2 debt Muscle Energetics The immediate source of energy to support development of tension ATP 1 Hydrolysis by the myosin head group fuels tension generation 2 Hydrolysis by the Ca pump of the SR supports relaxation Where does the ATP come from 1 2 3 4 Cell pool of ATP Creatine Phosphate Anaerobic Glycolysis glucose breakdown Aerobic metabolism glucose from glycogen fatty acids from lipids amino acids from proteins Where does the ATP come from 1 Cell pool of ATP ATP resynthesis ATP is not stored only enough to support 2 sec of maximal force Where does the ATP come from 2 Creatine Phosphate CP pool CP stores high energy phosphate creatine phosphokinase CPK CPK CPK the CP pool has enough high energy phosphate to support 15 sec of maximal contraction Creatine Phosphate Pool After a meal ATP C ADP CP During exercise ADP CP ATP C Creatine Creatine is a small amino acid like molecule that is synthesized in the liver kidney and pancreas and transported to muscle fibers In a relaxed muscle fiber creatine is 3 6 times more plentiful than ATP Where does the ATP come from 3 Glycogen used anaerobically glycolysis occurs in the cytoplasm occurs rapidly can support 2 min of contraction Where does the ATP come from 4 Glycogen fat and protein used aerobically occurs in the mitochondria relatively slow can support 40 min to several hours of contraction intensity dependent SI Integration Session Next Tuesday Looking for an opportunity to practice applying the information that you have been studying for your exam on Wednesday Come join your peers at our integration session this upcoming Tuesday October 27th from 6 00 8 00 pm at Park Student Union upstairs in the Javelina room This integration session will be a cumulative application based session that includes fun collaboration with your fellow classmates and engaging group activities We hope to see you all there Energy Metabolism in the Cell anaerobic glycolysis only aerobic glycolysis oxidative phosphorylation MITOCHONDRION ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP Glucose ADP Pi Glucose ADP Pi ATP Pyruvate Lactate plasma membrane ATP Clicker questions Clicker channel 70 Response Ware session ID psio201 At rest creatine phosphate levels are A low B high 76 24 A B The fastest method of ATP resynthesis in skeletal muscle is A B C D Creatine phosphate Anaerobic glycolysis Aerobic glycolysis Anaerobic fatty acid oxidation E Aerobic fatty acid oxidation 64 24 10 A B C 1 2 D E Which method of ATP resynthesis is predominantly used to produce ATP in skeletal muscle at rest 69 A Creatine phosphate B Anaerobic glycolysis C Aerobic oxidation of glucose fatty acids or amino acids 24 7 A B C Contribution of energy systems to ATP resynthesis Fatigue Cost of Peak Activity Progressive increase in the effort required to maintain a desired force and a progressive inability to maintain this force in sustained or repetitive contractions There are many sources of fatigue Psychological Nervous System Muscle Fatigue Cost of Peak Activity Possible Causes Glycogen depletion Lactic acid buildup from anaerobic glycolysis Phosphate buildup from creatine phosphate metabolism Cori Cycle muscle 2 1 Glucose Lactic acid liver O2 Debt a k a Excess Post exercise Oxygen Consumption O2 Consumption cost of resetting the system after exercise O2 debt Time Metabolic Equivalents METS University of Colorado http www colorado edu epob epob1220lynch 08muscle html Elevated O2 consumption after exercise 1 Lactic acid conversion back to glycogen in the liver Cori cycle 2 Resynthesize creatine phosphate 3 Replace oxygen removed from myoglobin 4 Repair Other reasons Suggested Learning Activities Create a table of the three methods by which the cell can resynthesize ATP and compare oxygen use ATP produced location of reactions speed of reactions substrates used and duration Draw a graph representing oxygen debt and explain why it takes time for oxygen consumption to return to rest