1. Skeletal Muscle Contraction Notes

2. Review Epimysium (outer covering of muscle) Fascicle (bundle of muscle fibers) Perimysium (covering fascicle) Endomysium (covers each muscle fiber)

3. Myofibril (bundle in each muscle cell – made of actin & myosin)

4. H - zone Z - line sarcomere A bandI band Which band is the thin filament?ACTIN Which band is the thick filament? MYOSIN

5. More Interesting Muscle Facts Your muscles are what percentage of your body weight? 40% - 50%

6. What percentage of muscle is made of water? 75%

7. SKELETAL MUSCLE CONTRACTION 8 Steps STEP I an action potential travels along a neuron to a synapse at a muscle fiber

8. STEP II ACETYLCHOLINE (a neurotransmitter) is released from the neuron STEP III Acetylcholine binds to muscle cell membrane

9. STEP IV sodium ions diffuse into the muscle fiber, starting an action potential STEP V Calcium ions are released from the sarcoplamic reticulum and bind to actin

10. STEP VI myosin attaches to actin forming CROSS - BRIDGES STEP VII myosin pulls the actin causing it to slide over the myosin STEP VIII ATP attaches to myosin and supplies the energy for the myosin to pull the actin