In the CNS, where is the key regulators of sleep located?

The normal circadian rhythm is regulated by the paired suprachiasmatic nuclei of hypothalamus, one on either side above the optic chiasm. These nuclei receive information about the light dark cycle special neural pathway, the retinohypothalamic fibers that pass from the optic chiasm to the suprachiasmatic nuclei. Efferents from the suprachiamatic nuclei initiate neural and hormonal signals that entrain a variety of well known circadian rythms. These include rythms in the secretion of ACTH and other pituitary hormones, sleep wake cycle, activity patterns and secretion of pineal hormone melatonin. Ref: Harrison's Principles of Internal Medicine, 16th Edition, Page 155; Textbook of Medical Physiology By Guyton and Hall, 10th Edition, Page 689, 690