Monday, October 12, 2009

Explains the steps in contraction of a sarcomere.?

Sarcomere :the smallest contractile unit of muscle;extends from one Z disc to the next.
Who can outline the steps.
I hope some one tell me about it in medicine and what's the different if some one outline the steps with (biology) science%26gt;
Inside of a muscle fiber, the individual sarcomere is the smallest unit of muscular structure that ultimately leads to the contractions necessary for force generation in response to stimulation. The cycle proceeds as follows:
1) The motor nerve ending releases the signal to stimulate the muscle membrane to induce an action potential.
2) The action potential spreads away from the neuromuscular junction and enters the transverse tubule system.
3) Ionic changes in the T-tubules lead to depolarization of the internal sarcoplasmic reticulum where the two membranes come to close apposition.
4) Calcium is released from the SR through ryanodine receptors and this causes the start of the contraction cycle.
5) Myosin head groups engage the thin filaments (of actin) and wait for release of the inhibition of the troponin regulatory molecules.
6) The power stroke of the myosin molecule takes place with the hydrolysis of ATP, causing contraction.
7) Calcium is pumped out of the cytoplasm and back into the sarcoplasmic reticulum through the action of calcium re-uptake channels.
8) The contraction cycle is stopped by the action of the troponins, and the thick and thin filaments release and slide past each other again to their resting state.
Please see the webpages for more details on Sarcomere.

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