system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do our brains know when to wake up? What keeps us from just staying asleep forever until something disturbs us?
gpt
Histamine and melatonin are the two cycles. Histamine builds while you sleep, melatonin while you are awake. Thus if you take benadryll (histamine blocker) you get tired, or take melatonin to help you sleep. These are controlled by the thalamus on the dopamanergic pathway, hence stimulants wake you up.