Two influences on sleepiness
Compare accumulating sleep pressure with a daily alerting rhythm.
The picture in words
- Sleep pressure
- The need for sleep grows with time awake and eases during sleep.
- Daily rhythm
- Circadian timing influences alertness across the day.
Reading the illustration
Compare the curves over the same period. Their heights are schematic and use separate conceptual scales.
Try a question
Why might equal amounts of time awake feel different at different times of day?
Show the explanation
Sleep pressure and circadian timing both contribute. The diagram separates their roles to make the comparison easier.
Read the sources
- National Heart, Lung, and Blood Institute. (2022b, March 24). How sleep works: Your sleep/wake cycle. https://www.nhlbi.nih.gov/health/sleep/sleep-wake-cycleSelected rendered passages: environmental cues and the biological need for sleep.