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How DO muscles contract

Page history last edited by Cherelle Hurley 7 years, 12 months ago

How DO muscles contract??

By: Cherelle Hurley



Muscle contraction by definition is the shortening of a muscle, in the muscular system besides shortening its creating tension.  Contraction is done by a process called "Sliding Filament Theroy," there are many things that occur within the muscle involved in the contraction.  To begin we need to define a few critical words that are most important within the contraction.


Sarcomere: functional unit of myrofibrial

Actin: Protein within thin filament

Myosin: Protein within thick filament

ATP: Converted to ADP, creates calcium pump
Action Potential: Change in electrical charge (impulse)

Cross Bridges: Connection between myosin molecule and actin filament

I-bands: Isotrophic, light colored, thin filaments (action only)

A-bands: Anisotrophic, darker colored, thick filaments (myosin only)

Sarcoplamic reticulum (SR): Similar to ER, resoponsible for storing and release calcium ions


So......... How DO muscles contract??

The answer is the "Sliding Filament Theroy," which is essentially the process of how a muscle contracts.  It is the shortening of the sarcomere (fuctional unit of a muscle)


(1st) Nerve impulse, action potential (from CNS) sent across the sarcomere

(2nd) Resulting from the impulse, Acetyclhoine - cause the SR releases Ca ++

(3rd) High concentration of Ca++ in the cytoplasm allows myosin (thick/A-band) head to attach to ATP, being energized and charged  it binds to actin (thin/I-band)

(4th) This force (power stroke) give it the ability for the thin and thick filaments to slide across one another (Creating a cross bridge)

^^ this makes the muscle contract and shortening of sarcomere ^^



Image reference: http://www.clt.astate.edu/mhuss/Chapter%209%20-%20Muscular%20System_files/slide0011_image031.jpg



Written reference: http://www.answers.com/topic/sliding-filament-theory



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