Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Pages 187-195 Muscle fiber contraction is “all or none” ◦ There is no “in-between” contraction Not all fibers may be stimulated at one time Different combinations of muscle fiber contractions may give differing responses ◦ Graded responses= different degrees of skeletal muscle shortening © 2015 Pearson Education, Inc. Graded responses can be produced by changing: ◦ The frequency of muscle stimulation ◦ The number of muscle cells being stimulated (and therefore, recruited) at one time more fibers= greater muscle tension ◦ Muscles can contract until they run out of energy © 2015 Pearson Education, Inc. Adenosine Triphosphate (ATP) ◦ Immediate source ◦ Stored in muscle fibers in small amounts that are quickly used up After this initial time, other pathways must be utilized to produce ATP © 2015 Pearson Education, Inc. 1. Direct phosphorylation of ADP ◦ by creatine phosphate 2. Aerobic (cellular) respiration (most ATP) 3. Anaerobic (cellular) respiration ◦ glycolysis and lactic acid formation © 2015 Pearson Education, Inc. Muscle cells store CP, a high-energy molecule ◦ After ATP is depleted, ADP remains ◦ CP transfers a phosphate group to ADP to regenerate ATP ◦ CP supplies are used up in less than 15 seconds (About 1 ATP is created per CP molecule) *creatine phosphate is also known as phosphocreatine © 2015 Pearson Education, Inc. Figure 6.10a Methods of regenerating ATP during muscle activity. (a) Direct phosphorylation Coupled reaction of creatine phosphate (CP) and ADP Energy source: CP CP Creatine ADP ATP Oxygen use: None Products: 1 ATP per CP, creatine Duration of energy provision: 15 seconds – breaks down glucose without oxygen – broken down to pyruvic acid, then to lactic acid – produces about 2 ATP very quickly – Lactic acid accumulates in the muscles and produces fatigue – After exercise, the oxygen deficit is repaid by rapid, deep breathing © 2015 Pearson Education, Inc. Figure 6.10b Methods of regenerating ATP during muscle activity. (b) Anaerobic pathway Glycolysis and lactic acid formation Energy source: glucose Glucose (from glycogen breakdown or delivered from blood) Glycolysis in cytosol O2 2 ATP net gain Released to blood Pyruvic acid O2 Lactic acid Oxygen use: None Products: 2 ATP per glucose, lactic acid Duration of energy provision: 40 seconds, or slightly more Glucose is broken down to CO2 and H2O ◦ ◦ ◦ ◦ Creates about 32 ATP per glucose molecule occurs in the mitochondria slower reaction, requires continuous oxygen Provides hours of sustained energy © 2015 Pearson Education, Inc. See page 194 for this side-by-side comparison of pathways Comparison of pathways Image source:http://www.udel.edu/chem/C465/senior/fall00/Performance1/phosphocreatine.htm.html • Isotonic contractions – Myofilaments slide past each other during contractions – The muscle shortens, and movement occurs – Example: bending the knee; rotating the arm • Isometric contractions – Tension in the muscles increases – The muscle doesn’t shorten or produce movement – Example: pushing against a wall with bent elbows © 2015 Pearson Education, Inc. Increase in muscle: ◦ ◦ ◦ ◦ Size Strength Endurance Aerobic (endurance) exercise= stronger more flexible muscles greater resistance to fatigue ◦ Resistance, or isometric, exercise like weight lifting increases muscle size and strength © 2015 Pearson Education, Inc.