Origin - point of a muscle that is attached to the immovable, or less moveable bone.

2. Origin- point of a muscle that is attached to the immovable, or less moveable bone. • Insertion- attached to the movable bone, and when the muscle contracts, the insertion moves toward the origin.

4. The “All-or-None” Law • Some muscles have interchangeable origins and insertions • The “all or none” law of muscle physiology applies to the muscle cell not the whole muscle. • It states that a muscle cell will contract to its fullest extent when it is stimulated adequately; it never partially contracts.

5. Muscle Response to Increasingly Rapid Stimulation • 1. Twitch-a single stimulus is delivered, the muscle contracts and relaxes (a twitch contraction)

6. 2. Summing of contractions-stimuli are delivered more frequently, so the muscle does not have time to completely relax; the individual twitches are summed

7. 3. Unfused (incomplete) tetanus-more complete fusion of the twitches occurs as stimuli are delivered at a still faster rate

8. 4. Fused tetanus-a smooth continuous contraction without any evidence of relaxation, results from a very rapid rate of stimulation.

9. Energy Sources for Muscles • Muscle contractions take a lot of energy in the form of ATP • Muscles get their ATP from 3 sources: • The breakdown of creatine phosphate • Cellular respiration • Fermentation

10. Creatine Phosphate Break Down • Creatine phosphate regenerates ADP to make ATP • Gives quick energy for few seconds • Only 1 ATP produced per creatine phosphate • Oxygen is NOT needed • When a muscle is resting, the ATP in turn regenerates creatine phosphate

11. Cellular Respiration • Happens in mitochondria • Glucose is broken down to produce ATP • Oxygen is necessary and carbon dioxide is produced as a waste product • Can provide energy for hours • Produces 36 ATP per glucose molecule • Fatty acids and amino acids can be used for energy sources also

12. Fermentation • Occurs in cytoplasm • Cell only uses glycolysis to break glucose down into lactic acid • No oxygen is required • Provide energy for 30-60 seconds • 2 ATP produced per glucose molecule

14. Muscle Fatigue • When a muscle is unable to contract even though it is being stimulated; believed to be due to oxygen debt. True muscle fatigue is rare because we slow or stop our activity long before we reach true fatigue. • Common in marathon runners who literally collapse when muscles cease to work • We breathe heavily, even after an activity is complete, to help “repay” the oxygen debt.

15. Types of Muscle Contractions • Isotonic contraction- muscle shortens, movement occurs. Ex: lifting a book, smiling, bending the knee, rotating the arms, etc. • Isometric contraction- muscles do not shorten. Ex: holding a book in an outstretched arm. • Isometric contractions result in increases in muscle tension, but no lengthening or shortening of the muscle occurs.

16. Effect of Exercise on Muscle • Aerobic, endurance exercise results in stronger, more flexible muscles, with greater resistance to fatigue- greater blood supply, more mitochondria, and store more oxygen. • Biking, jogging, aerobics classes • Resistance exercise causes bigger, stronger muscles by enlarging individual muscles cells and more connective tissue. • Weight lifting

17. Interactions of Skeletal Muscles • Prime mover- muscle that has the major responsibility for causing a particular movement. • Antagonist- oppose or reverse the movement. Ex- biceps and triceps