Hey, welcome back.
You have to answer this using knowledge of the
sliding filament theory. Check the animations section for animations on this process or search the forum - lots of stuff available. Basically the sliding filament model explains how the myosin head moves down the actin polymer, generating movement. It starts when a neurotransmitter, acetylcholine, is released unto skeletal muscles. When acetylcholine binds to acetylcholine receptors on skeletal muscle fibers, it opens ligand-gated sodium channels in the cell membrane. Sodium ions then enter the muscle cell, initiating a sequence of steps that finally produce muscle contraction. When a muscle contracts, myosin molecules coil up like springs to shorten the length. Myosin is a motor protein that converts the chemical bond energy of ATP into the mechanical energy of motion. Each myosin molecule acts as an enzyme that both binds ATP and releases its energy, and the energy released by ATP produces the power stroke by swiveling the myosin head. As ATP binds to the myosin head at the beginning of a muscle contraction cycle, the myosin head detaches from actin.
This should help you get started, shaundavis24. Hope this helps!
Also, try this step-by-step animation:
http://bcs.whfreeman.com/thelifewire/content/chp47/4702001.htmlBio_man
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