system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: When you get so tired that you become physically sick (nauseous/headache/etc), what's actually happening to your body?
gpt
ELI5: The body is telling you to slow down after experiencing stress. Seek a doctor for medical advice.

Ext'd: Overexhaustion of the body can cause physical and emotional stress, which puts strain on the body's vascular system and can cause hormonal or behavioural changes. This can cause headaches and feelings of being tired or unwell. When the body is in a stressed state, opportunistic ailments such as bacterial infection or chemical imbalances can cause physical signs of illness or experiences of symptoms such as fatigue or nausea.