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Muscle Contraction - Medical Animation

 

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Muscle Contraction - Medical Animation
MEDICAL ANIMATION TRANSCRIPT:
Skeletal muscles are voluntary, controlled consciously by the nervous system, and are made up of fascicles, which are bundles of muscle fibers surrounded by connective tissue, blood vessels, and nerves. Motor nerve axons supply one or more skeletal muscle fibers, constituting a motor unit. Inside a muscle fiber, thread-like structures called myofibrils are organized into contractile units, or sarcomeres, reflecting the striations characteristic of skeletal muscle. Each sarcomere is made up of thick and thin myofilaments, strands of proteins called myosin and actin. Myosin forms thick filaments. Actin forms thin filaments. The protruding heads of myosin filaments form cross bridges that bind to actin filaments and ATP, an energy transport molecule. Thin filaments contain a sequence of actin molecules with myosin-binding sites. At rest, actin molecules bind tropomyosin and troponin, two contractile proteins that inhibit contraction. Skeletal muscle contraction begins at the muscle fibers' plasma membrane, or sarcolemma, with invaginations called transverse or T-tubules that surround each myofibril, and open to the extracellular space. T-tubules connect to a membranous network called the sarcoplasmic reticulum that store calcium and transfer ions via voltage-gated channels into the myofibril sarcoplasm to regulate muscle contraction. In the first step of muscle contraction, called excitation, a motor nerve fires an impulse, or action potential, across the neuromuscular junction, depolarizing the sarcolemma, and generating an action potential that spreads through the sarcolemma into the T-tubules, and excites the muscle fiber. The second step is coupling, wherein the action potential depolarizes the T-tubules. Channels in the sarcoplasmic reticulum release calcium into the sarcoplasm. Along the myofilaments, troponin binds calcium and separates from tropomyosin. In the third step, called contraction, tropomyosin shifts away from actin to expose the myosin-binding sites, enabling myosin to bind to actin, resulting in the activation of ATP and the cross bridges. Released energy causes the myosin heads to rotate and pull the thin filaments inward, sliding past the thick filaments and shortening the sarcomere. The fourth step of muscle contraction is relaxation, in which calcium ions return to the sarcoplasmic reticulum and break the myosin-actin bonds. The cross bridges disengage, and the sarcomere lengthens, resulting in relaxation of the muscle and the end of the contraction. ♪ [music] ♪

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What attorneys say about MLA and The Doe Report:
"I wanted to take some time out to let you know what a wonderful job you did with the 'collapsed lung/fractured rib' illustrations. They were both detailed and accurate. My medical expert was comfortable working with them and he spent at least an hour explaining to the jury the anatomy of the lungs, the ribs and the injuries depicted in the illustrations. Needless to say, the jury was riveted to the doctor during his testimony.

The jury returned a verdict for $800,000.00 and I'm sure we would not have done so well if not for the visualizations we were able to put forth with your assistance. Lastly, my special thanks to Alice [Senior Medical Illustrator] who stayed late on Friday night and patiently dealt with my last minute revisions."

Daniel J. Costello
Proner & Proner
New York, NY

"I just wanted to let you know that after several days on trial, I settled [my client's] construction accident case for $4.5 million. Immediately after the jury was discharged, I spoke with several jurors who told me that they really appreciated the medical illustrations for their clarity in dealing with [my client's] devastating injuries. They also expressed their gratitude in being able to read from a distance all of the notations without difficulty. Obviously, the boards were visually persuasive. I am certain that this contributed to our successful result."

Michael Gunzburg, Esq.
Attorney at Law.
New York, NY

"This past year, your company prepared three medical illustrations for our cases; two in which we received six figure awards; one in which we received a substantial seven figure award. I believe in large part, the amounts obtained were due to the vivid illustrations of my clients' injuries and the impact on the finder of fact."

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Marcari Russotto & Spencer, P.C.
Chesapeake, VA
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I highly recommend MLA to anyone seeking high quality, detailed medical legal artwork."

E. Marcus Davis, Esq.
Davis Zipperman, Krischenbaum & Lotito
Atlanta, GA
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