Question

The brain's pineal gland produces the hormone ________, which helps control your sleepiness and wakefulness cycles.

Answer 1

The brain's pineal gland produces the hormone melatonin,  which helps control your sleepiness and wakefulness cycles. Melatonin is a natural hormone in the body which production is stimulated by darkness and decreased by light.  This hormone is involved in the internal body clock and regulates diverse body functions.

Answer 2

Melatonin is the hormone produced by the brain's pineal gland. This hormone helps in regulating one's sleep cycle - i.e. controls sleepiness and wakefulness.