The suprachiasmatic nucleus is considered to be our sleep center. When it senses light, it tells the pineal gland to suppress melatonin. Decreasing melatonin is what triggers us to switch from sleeping to wakefulness. This is when we experience wakeup cues such as an elevated heart rate, a rise in body temperature, and increased cortisol levels. This process results in our “rise and shine” response every day.