Final answer:
The hypothalamus is the part of the brain that controls arousal, consciousness, and sleep, whereas the pineal gland produces melatonin, which influences sleep patterns.
Step-by-step explanation:
The part of the brain that controls your level of arousal or consciousness and sleep is the hypothalamus. The hypothalamus is a region of the diencephalon that coordinates homeostasis. It sits inferior and somewhat anterior to the thalamus and is considered the master control center for homeostasis through the autonomic and endocrine systems.
The hypothalamus contains the suprachiasmatic nucleus (SCN), which is often referred to as the body's biological clock. It is involved in regulating circadian rhythms, including the sleep-wake cycle. The hypothalamus works in conjunction with other areas such as the thalamus and the pons to regulate the different stages of sleep, including REM and slow-wave sleep.
The pineal gland, also part of the diencephalon and located inferior and posterior to the thalamus, produces the hormone melatonin. Melatonin is associated with the regulation of sleep patterns and is produced in response to darkness, helping to induce drowsiness.