1. Pages 187-195

2.  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.

3.  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.

4.  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.

5. 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.

6.  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.

7. Figure 6.10a Methods of regenerating ATP during muscle activity. (a) Direct phosphorylation CP ADP ATP Creatine Coupled reaction of creatine phosphate (CP) and ADP Energy source: Oxygen use: Products: None 1 ATP per CP, creatine 15 seconds Duration of energy provision:

8. – 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.

9. Figure 6.10b Methods of regenerating ATP during muscle activity. glucose Energy source: Glycolysis and lactic acid formation (b) Anaerobic pathway ATP 2 O2O2 O2O2 Oxygen use: Products: Duration of energy provision: None 2 ATP per glucose, lactic acid 40 seconds, or slightly more net gain Released to blood Glucose (from glycogen breakdown or delivered from blood) Pyruvic acid Lactic acid Glycolysis in cytosol

10.  Glucose is broken down to CO 2 and H 2 O ◦ 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.

11. See page 194 for this side-by-side comparison of pathways

12. Comparison of pathways Image source:http://www.udel.edu/chem/C465/senior/fall00/Performance1/phosphocreatine.htm.html

13. 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.

14.  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.