1. Figure 10.12 The Contraction Cycle Figure 10.12

2. Figure 10.12 The Contraction Cycle Figure 10.12

3. Acetylcholinesterase breaks down ACh Limits the duration of contraction Relaxation Animation: Sliding filament theory PLAY

4. All or none principle Amount of tension depends on number of cross bridges formed Skeletal muscle contracts most forcefully over a narrow ranges of resting lengths Tension production by muscle fibers

5. Figure 10.13 Figure 10.13 The Effect of Sarcomere Length on Tension

6. Twitch –Cycle of contraction, relaxation produced by a single stimulus Treppe –Repeated stimulation after relaxation phase has been completed

7. Repeated stimulation before relaxation phase has been completed –Wave summation = one twitch is added to another –Incomplete tetanus = muscle never relaxes completely –Complete tetanus = relaxation phase is eleminated Summation

8. Figure 10.14 Figure 10.14 The Twitch and the Development of Tension

9. Figure 10.15 Effects of Repeated Stimulations Figure 10.15

10. Internal tension generated inside contracting muscle fibers External tension generated in extracellular fibers Tension production by skeletal muscles

11. Figure 10.16 Internal and External Tension Figure 10.16

12. Motor units –All the muscle fibers innervated by one neuron –Precise control of movement determined by number and size of motor unit Muscle tone –Stabilizes bones and joints