No cause for alarm

The human body is an amazing piece of equipment. As a student of biology I have a reasonable understanding of some of the functionality of this kit; I've read some of the instructions. But other aspects of the human physiology remain a complete mystery to me. One of these is the body clock.

How does the body maintain it's own time system? Through most of the winter, my alarm has been set to 7:15 on work days. Yet the bulk of the time I wake up naturally at 7:14 anyway! How does the body know to pre-empt the rude awakening of the alarm? And to be so accurate about it?! I remember as a kid those sleepless nights when you knew you had to be up early for whatever reason, and then barely got a wink of sleep all night as a result. Now my body compensates and calculates the most efficient time to rise.

What confuses me even more is how, on days when I set my alarm to another time, my body somehow adjusts to this new time, and still rises from it's slumberous state a mere moment prior to the electronic noise of dawn. If I asked someone to set my alarm to a completely random time, unknown to me, would my body be fooled?!

On the occasions when I actually remain asleep until the alarm sounds, my body goes through a bizarre process of waking, vague comprehension and recollection and then understanding in just a few seconds. During this period I am able to open my eyes, roll over and turn the alarm off, and I wonder how I moved so seamlessly from one state to another. Some days the comprehension takes longer than others, and sometimes the understanding doesn't fully click in until around lunch.

When my alarm is activated, there is a mechanical click before the electronic beeping. The click sounds regardless of whether the alarm is on or off, as the clock hands pass the alarm hand. When I'm lying in bed on days when I haven't set the alarm, and I hear the click, my body goes through the same wakening process as if the alarm had gone off. It pre-empts what normally happens, and some kind of chemical reaction causes me to become alert very suddenly, as though adrenaline has been pumped into my system. Which is slightly disconcerting.