Figure The Contraction Cycle Figure 10.12

Figure The Contraction Cycle Figure 10.12

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

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

Figure Figure The Effect of Sarcomere Length on Tension

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

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

Figure Figure The Twitch and the Development of Tension

Figure Effects of Repeated Stimulations Figure 10.15

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

Figure Internal and External Tension Figure 10.16

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