Sleep

For the past week or so, I've been wondering what it is about sleep that dulls one's instincts. Why is it that I am able to suppress the urge to cough or go to the bathroom while sleeping, when as soon as I wake up I become strongly aware of them? Does something happen while I sleep that blocks receptors which would normally send signals to my brain, making me aware of my body? Also, what distinguishes sleep from simple unconsciousness or a coma, making it possible for me to wake up after a number of hours?

I've been researching this topic lightly on wikipedia, and concluded that I need to know more about adenosine. Adenosine is the combination of Adenine (one of the nitrogenous bases in DNA) and a ribose sugar (so it's like a nucleotide without the phosphate group). Apparently, adenosine is a neurotransmitter that builds up in the body over the course of a day, and high concentrations of adenosine make people sleepy. In addition, caffeine can bind to some of the same receptors as adenosine, acting as an inhibitor that blocks adenosine from binding to the receptor. I had read that caffeine allows people to maintain their current state of wakefulness, so that instead of getting drowsier it keeps you at the same state of sleepiness. This makes sense, if it is keeping the adenosine that continues building up in your body from acting on your receptors and making you sleepy.

Sleep also is promoted by the release of the hormone melatonin, which is only produced when it's dark, and how long you need to sleep to feel rested is partially genetic (at least one gene that regulates this has been discovered). I am still trying to find out exactly what causes me to be unaware of my senses during sleep - a quick google search didn't give me any answers so I'll have to go more in depth. It's funny to me, though, that every time I look for an answer to a scientific question, I always find new information that makes me want to ask more questions.