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