system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why do we get "second winds" after long periods of fatigue/being tired, and how do they work, physiologically?
gpt
If you keep pushing your body to keep going, it knows that you need to be awake/alert/not hungry in order to survive. So, it releases adrenaline, dopamine and other hormones/neurotransmitters that suppress hunger, sleep and make you feel better. It is the body's natural equivalent for man made stimulants like speed. Even though the body's response is chemical, the result is psychological stamina (which does come to an end when chemicals are completely depleted and you crash).