Muscle ContractionsFigure 39-4

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. An __________________travels down a motor neuron

2. The skeletal muscle _________ is activated at the ____________________ junction

3. An _____________________travels down the muscle __________________________

4. The action potential enters _____________5. 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

http://upload.wikimedia.org/wikipedia/commons/6/6e/Sarcomere.svg

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