system
Given the following post, respond as if you're commenting on Reddit:
human
[Neuroscience] Why can't we use adrenaline or some kind of stimulant to wake people out of comas? Is there something physically stopping it, or is it just too dangerous?
gpt
Adrenaline, cortisol, and other stimulants are like an alarm. They're a chemical signal that can quickly travel around the body.

People fall into comas for many reasons, but generally increasing the 'wake up' signal won't do anything. It's like a ringing alarm clock for a deaf person.

Most comas are caused by drug overdose of one kind or another. This tends to cause coma through damage to a region of the brain stem called the Ascending Reticular Activating System (ARAS). In particular, synaptic function is impaired. Basically the neurons that form the 'wake up' button lose the ability to talk to each other. Pressing the button harder won't make a difference.

Other times, there's systemic damage to the brain. The 'wake up' button may work, but the stuff it's connected to can't sync up correctly. This is particularly true for damage to the outer layer of the brain - the cerebral cortex - which is where consciousness seems to happen.