Muscle Contractions

1. Figure 39-4 Muscle Contractions

2. Sliding Filament Mechanism • _________ and_______filaments slide over each other______________the muscle length • Always requires ________ ions and ___

3. Actin • Double chain of ______ proteins • Makes up ____ filament • Attached to end walls of sarcomeres called _____ • Makes up __ band of sarcomere • Has ______ binding site which is blocked by ____________ and ____________ in relaxed muscle

4. Myosin • Makes up _______ filament • Has myosin ________ which bind to _______ • Make up ___ bands in a sarcomere

6. Neuromuscular Junction • “Joining” of motor ______ and ___________ • _______________-motor neurons release _________________ that diffuse across synapse to receptors on muscle fiber membrane • Always ______________ • Motor unit-_______branched motor ________ synapsing with ______ muscle _______

8. 11 Steps of a Muscle Contraction • An __________________travels down a motor neuron • The skeletal muscle _________ is activated at the ____________________ junction • An _____________________travels down the muscle __________________________ • The action potential enters _____________ • An action potential stimulates the ____________________________________

9. 11 Steps of a Muscle Contraction Cont. 6. ______________________are released into the muscle cell ____________________ 7. _____________ ions bind to _____________ 8. ___________________ exposes ___________ binding sites on _________ 9. Myosin _______ bind to ________ 10. Myosin heads __________ 11. _______ filaments are pulled toward sarcomere center, and muscle fiber ________

10. Muscle Relaxation • When action potential is over, ________ goes back to _______________________________ • Calcium is removed from _____________ • Troponin and tropomyosin ________ myosin binding sites • Muscle ____________

11. 1 - Calcium released from sarcoplasmic reticulum 2  - Myosin head energized via myosin-ATPase activity which converts the bound ATP to ADP + Pi 3 - Calcium binds to troponin 4 - Tropomyosin translocates to uncover the cross-bridge binding sites 5 - The energized myosin binding sites approach the binding sites 6 - The first myosin head binds to actin 7 - The bound myosin head releases ADP + Pi, flips and the muscle shortens 8 - The second myosin head binds to actin 9 - The first myosin head binds ATP to allow the actin and myosin to unbind 10 - The second myosin head releases its ADP + Pi, flips & the muscle shortens further 11 - The second myosin head binds to ATP to allow the actin and myosin to unbind 12 - The second myosin head unbinds from the actin, flips back and is ready for the next cycle 13 - The cross-bridge cycle is terminated by the loss of calcium from the troponin 14 - Tropomyosin translocates to cover the cross-bridge binding sites 15 - The calcium returns to the sarcoplasmic reticulum, the muscle relaxes & returns to the resting state

13. Contraction Clip • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__sarcomere_contraction.html http://www.youtube.com/watch?v=EdHzKYDxrKc&feature=player_embedded http://www.youtube.com/watch?v=gJ309LfHQ3M&feature=player_embedded