Figure 39 4 Muscle Contractions Sliding Filament Mechanism

Figure 39 -4 Muscle Contractions

Sliding Filament Mechanism �_____ and_______filaments slide over each other_______the muscle length �Always requires ____ ions and ___

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

Myosin � Makes up _______ filament � Has myosin ____ which bind to _______ � Make up ___ bands in a sarcomere

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 _______

11 Steps of a Muscle Contraction 1. 2. 3. 4. 5. 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 __________________

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 ____

Muscle Relaxation �When action potential is over, ____ goes back to ________________ �Calcium is removed from _______ �Troponin and tropomyosin ____ myosin binding sites �Muscle ______

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

Contraction Clip �http: //highered. mcgraw- hill. com/sites/0072495855/student_view 0/cha pter 10/animation__sarcomere_contraction. h tml http: //www. youtube. com/watch? v=Ed. Hz. KYDxr. Kc&feature =player_embedded http: //www. youtube. com/watch? v=g. J 309 Lf. H Q 3 M&feature=player_embedded