What in the hell is a "headache"?!
Question:
What in the hell is a "headache"?
In my 30 years of life I've experienced many "headaches", some worse than others, but all a pain just the same. I just so happen to have one right now, and the pain is so demanding it has left me wondering.... What in the hell is a "headache"? What is actually happening in the human skull while experiencing a "headache"? Does the brain swell? Does nerves behind our eye sockets swell? What.....?
Answers:
It's a 'ache' in your head. ;-p
Seriously....you ask a great question! Evidently docs think the generic headache is circulation based, which is why many throb, and why alot of the migraine drug regulate the dilation and constriction of blood vessels. (I have migraines, but that doesn't explain the light & noise sensitivity)
Of course other things can cause headaches, like some of the things you mentioned, but those are 'conditions' which the pain is just a symptom of the problem. At least in that case when you solve the problem, the headache goes away and doesn't return, at least not for that particular reason.