Final answer:
Circadian rhythms are our natural daily patterns of waking and sleep. The pineal gland is signaled by the hypothalamus in response to daylight or darkness, regulating the production of melatonin in our bloodstream. Melatonin levels are higher during daylight hours than at night.
Step-by-step explanation:
Our natural daily patterns of waking and sleep are called circadian rhythms. Our natural daily patterns of waking and sleep are called circadian rhythms. Exposure to daylight or darkness causes the hypothalamus to signal the pineal gland, which regulates the amount of melatonin in the bloodstream, so that production of this hormone is higher during daylight hours than at night.Our natural daily patterns of waking and sleep are called circadian rhythms. Exposure to daylight or darkness causes the hypothalamus to signal the pineal gland, which regulates the amount of melatonin in the bloodstream, so that production of this hormone is higher during daylight hours than at night. Exposure to daylight or darkness causes the hypothalamus to signal the pineal gland, which regulates the amount of melatonin in the bloodstream, so that production of this hormone is higher during daylight hours than at night.