system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does a mental illness such as anxiety mimic physical symptoms that could've be due to a physical health issue?

For example, I don't understand how your brain can make you feel chest pain, exhaustion, achy, short of breath, heart palpitations, etc, that could be symptoms of actual physical health issues.
gpt
Anxiety can release adrenaline. Adrenaline can increase heart beat which can cause palpations.

A panic attack causes hyperventilation. This makes a person exhale too much carbon dioxide (which is why they tell you to slow your breathing). Too little C02 in the blood stream (hypocapnia) can cause muscles to tense up. Fingers constrict and cant unbend. Chest muscles tense up too and can cause pain.