"I pinch myself to make sure I am not dreaming." I think there is a similar expression world-wide and that it indicates pain wakes you up. Is this true? For example, if you pinch yourself when you feel sleepy at work or in a lecture, does that wakes you up? Yes is the short answer, if the stimulus is good enough. Then How is it so?

Reticular formation: Pinching pain spreads your whole brain to wake you up!

There is a brain switch in our brain stem. (**) That is called the reticular formation, from which nerve fibers are radiated to every part of the brain cortex. And if reticular formation is stimulated, Action Potentials(*) or the "wake-up" signals are sent to the all part of cortex, which is the most outer part of the brain and responsible for conciousness.

Then what stimulates the reticular formation? One of the best, or I should say worst, stimuli is a pain. Actually a nerve signal, called Action Potential "drops by" the Reticular formation, while the AP travels from the pain area to the sensory brain cortex (post-central gyrus/primary sensory cortex*). Therefore if you have a pain, your whole part of brain is stimulated via the RF and that wakes your brain up.

That is how your sleep will be significantly disturbed when you have serious pain. At terminal stage of a cancer, sleep disturbance is a common complaint. One of my chinese friend yesterday told me that he has a back pain so that he can not sleep. This is not a dead or alive situation but obviously this disturbance decreases his quolity of life. It indicates that pains wake your brain up. (***)

It makes sense, right? Pain is a good alert for danger to your body; the body is notifing the brain that you should not sleep now, something is wrong, take an action!

Also maybe you know from your experiences that Exercise will wake your brain up. Because Motor pathway (Descending Pathway*)also "drops by" Reticular formation, which stimulates and wake your whole brain up. of course, you can not do exercise during a lecture.

Oh, maybe a cup of coffee is the best solution for the lecture situation; simple and smart enough. But sometimes you don't have it. Then pinch your self hard enough! That will do. Or the best solution is sleep during the lectrue because you are sleepy and that is what your body is wanting :)

*Note: good to know for medical-students. but a bit too much for non-doctors.

**Note: Dr. Najeev used this expression, a brain switch. And he enphasized that this is the one you have to know, if you choose to know one thing about the Reticular Formation. So this is the most important thing for RF, even for medical students.

***Note: In either case, if reticular formatin is silenced by a drug, patients will theoretically get easier to sleep, although this does not silence your pain. Once pain is silenced or the cause of pain is removed, meaning no AP of sensory fibers, there is no reticular formation simulation and sleep disturbance is also removed. The most common drug is, of course, pain killer, when the cause of pain can not be removed, like in case of chronic diseases.