... production of Per-Tim. As Per-Tim decreases, Clock-Cycle rises ready to begin the next cycle. Even if the details may vary from organism to organism, this core loop appears to be the centre of the endogenous biological clock mechanism in organisms. Another endogenous pacemaker, said to be the main is the suprachiasmatic nucleus (SCN). The SCN is a tiny cluster of nerve cells which lies in the hypothalamus. It is a pair of structures with one half on the left side of the brain and one on the right. Its job is to information on light from the optic nerve, even if your eyes are closed. If our endogenous clock is running slowly then the morning light will automatically shift the clock ahead putting the rhythm in step with the outside world. Light is an exogenous factor and recently has been seen as one of the most important of the exogenous factors to ...

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