Instructional Design: Website Design

10 12 2009

For this assignment we were asked to remake a website that happen to need major help. This is the website: Baltimore Massage Therapy

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Last Anatomical Visualization Assignment

10 12 2009

Background

The sliding filament theory is well accepted as the basic mechanism for muscle contraction. Two groups in England,

A.F. Huxley and Niedergerke (1954), and H.E. Huxley and Hanson (1954) are the founders of the theory. Here are two

early references:

Huxley, A. F. and R. Niedergerke. 1954. Structural changes during contraction: Interference microscopy of living muscle fibers. Nature 173: 971-973.

Huxley, H. E. 1969. The mechanism of muscle contraction. Science 164: 1356-1365.

A skeletal muscle is made up of long muscle fibers (muscle cells) which, in turn, are composed of bundles of myofibrils. Each myofibril consists of two kinds of protein filaments (sometimes called myofilaments) – thick filaments made of myosin and thin filaments made of actin. Myofilaments do not extend the full length of a muscle fiber; they are stacked together in compartments called sarcomeres. The sliding filament theory suggests a sliding of thick and thin filaments over one another thereby shortening the sarcomere.

Sliding of the filaments depends on the interaction of actin and myosin molecules. Myosin filaments are long and thin with rounded “heads” projecting out at the sides. The myosin heads connect the thick with the thin filament. This connection is called the myosin crossbridge, and the activity of the myosin head that results in muscle contraction is the myosin crossbridge cycle.

At rest, myosin is prevented from binding with actin molecules by the protein tropomyosin. Troponin controls the position of tropomyosin on the thin filament. However following stimulation by a motor nerve, acetylcholine diffuses from the neuron triggering the release of calcium ions into the sarcoplasm. Calcium ions bind to the troponin which then act on the tropomyosin molecule exposing the myosin-binding sites. Once the binding sites are open the myosin molecules form cross-bridges with the actin and the two filaments slide over one another.

At the resting state of the muscle ATP is bound to the myosin head, and the myosin head is not in contact with the thin filament. The hydrolysis of ATP provides the energy for the “recovery stroke” where the myosin head undergoes a conformational change bending forwards towards the N-terminal head domain of the myosin molecule (and towards the (+) end of the thin filament). ADP and Pi remain bound to the myosin head during the recovery stroke. The myosin head then contacts the thin filament, releases Pi and ADP, and at the same time conducts the “working stroke”. The working stroke is a second conformational change that brings the myosin head back into the position it had at the resting state. The thin filament moves in the direction of its (-) end because the myosin head is firmly attached to the thin filament during the working stroke. Finally, the myosin head binds one ATP molecule and detaches from the thin filament (the resting state).

Assignment 5

Create an illustration that explains the sliding filament mechanism theory of muscle contraction at the molecular level (the actomyosin crossbridge cycle). The emphasis of this assignment is to illustrate a process that occurs over a period of time with movement of certain elements over a finite distance. Include as many steps as necessary to explain the concept. Research for this project must include a survey of the scientific literature (journal articles). You will want to use other resources as well (textbooks, web references, content experts etc.), but at least three references must be journal articles.

The audience should be a professional one of your choosing. You also need to determine a journal page size for the final illustration. Typical page sizes might be 8.5 x ll or 7 x 9, for example. You may use more than one page if necessary.

A pencil sketch must be completed first on tracing paper. If you are comfortable with Adobe Illustrator, you may use the program to complete the final illustration. You are not required to produce anything more elaborate than a pencil illustration. Whatever method you choose for drafting the illustration, the lines and shapes must be cleanly drafted. If you are using pencil, this means relying on ellipse templates, french curves etc. Structures in the black and white diagram may be represented as outline, given a flat fill, or rendered.





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7 12 2009