What makes a snake shed?

I've gotten used to feeding my snakes, I've gotten used to holding them and how they act...
One thing I never get bored of is watching them throughout the entire shed cycle. It is fascinating to see.
But I was wondering about what happens "behind the scenes" on shedding. What makes a snake shed? Since their brain is only the survival part of a human brain (basically), but smaller, they obviously can't wake up and think about it and decide to. They act on instinct.
So, what makes them start the shed cycle? Why is it that the day before they enter the cycle they look fine, and the next day they are all dulled out and have a pink underside?
What makes the fluid build up under their scales? What makes the fluid clear up, and where does it go?
What part of the snake's brain tells it to start rubbing its nose on things, and how does the snake know to just start rubbing on stuff? :confused:
I hope there are some experts out there who can help me. I've been scratching my head over this since I got my first snake and watched her shed.
If no one can answer, well, I'm just so interested in this cycle of a snake's life that I would go to college and take classes and conduct studies just to find out. :)
But I hope someone knows now, because I don't want to be scratching my head for the next 8 years, driving myself crazy looking for the answer in school. :D
Also, what DOES a reptile's brain look like? What parts does it have?

(in case you haven't noticed, I'm a science and medical geek...biology, chemistry, anatomy, psychology...:D it makes my world go round)
Shellie

They dont think about it. It is involuntary as they grow, they get itchy and try to find a way to scratch it

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Originally Posted by ChuckSM

They dont think about it. It is involuntary as they grow, they get itchy and try to find a way to scratch it

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lol!!! :rofl:

they shed becouse their bodies grow, their scales dont.

our skin grows with us, theirs doesn't.

it gets tight and there in starts the begining.
it begins to losen from the new scales, slightly bigger than the last.
and a fact i just recently learned.

a snake continues growing and shedding till the day they die.

they never stop growing. interesting huh?

most animals stop at some point. lol

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Originally Posted by sookieball

our skin grows with us, theirs doesn't.
most animals stop at some point. lol

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It's not really that ours grows with us, as we grow little scraps of our skin fall off constantly as the new skin grows underneath. The majority of dust is made up of the little pieces of our shed skin. Snakes just shed their all at once.

There is a book that goes in depth on the Ball Python shedding process.
http://www.vpi.com/pythons_of_the_world_vol_2_0
This is by far the most in depth book about Ball Pythons and cover all you questions plus in depth about their biology, sight, breeding and care with a very cool section on morphs. I would highly recommend checking it out.