Which hormone produced by the pineal gland promotes sleepiness and helps regulate the sleep–wake cycle?

True or False: A 15-minute nap is more likely to improve immediate alertness without causing grogginess than a 40-minute nap.

Maria normally sleeps for 8 hours a night. Recently she's been waking up earlier due to work and has been averaging 6 hours of sleep per night for the past 14 days. What is her current sleep debt?

Which statement is the MOST accurate regarding human stress?

List and explain the four NREM sleep stages in the correct order.