:: The Physiology of Poker ::
Adrenaline is a strange and confusing creature. The more you understand it the more you come to realize it plays a large part in our everyday lives ... and an even larger part in poker. To understand it is to understand why people give off many of the tells they do and why they can't help it.
The body has a natural defense system known by most as 'fight or flight'. When you percieve danger your adrenal glands release adrenaline ... and let me tell you ... going all-in with only a pair of twos feels dangerous!
When the adrenaline hits your bloodstream your body begins preparing for actual fight or flight. The pupils dilate, letting in more information. When not preparing for a fight this makes things seem overly bright and a bit disorienting but in a fight or flight situation it lends to that wonderful 'time slowing down' sensation.
Next, the veins etc.. in your arms and legs constrict keeping blood flow to the hands/arms and feet/legs at a minimum. In fight or flight this would be to protect the instruments you'll be fighting or fleeing with (hands and feet) from bleeding when cut or scratched. Outside of that sort of situation it can cause the hands and feet to feel cooold.
Your body begins to coat itself with a sheen of sweat to give you slipperiness so you can avoid being grabbed or held.
Blood is devoted to circulating oxygen through your muscles and is diverted from your stomach. You begin to feel slightly nausious in an attempt to evacuate your stomach of any contents before fight or flight begins.
You stop producing saliva, your mouth and throat feel dry. This can cause lots of swallowing or water sipping in an attempt to alleviate the dryness.
Your oxygen usage is increased as your bloodstream starts transporting more of it to your muscles. Those muscles constrict, ready for action, and you feel you feel short of breath due to those increased demands for oxygen.
As your body prepares for action and you don't burn it off ... you begin to shake from all the extra oxygen and battle readiness in your muscles and long after the hand is over (approximately 5 minutes after the percieved danger is gone) your body releases a chemical to counter the adrenaline and your body finally begins to return to normal.
For the most part ... when you see a few of these signs in people it means they're trying to bluff or are commiting lots of chips on some kind of draw. If they really think they have a strong hand they would not percieve danger.
On the contrary ... I've noticed that lots of people's hands shake when they have a very strong hand. Personally I think this is just due to the excitement or they're holding their breath or something. Of course, there are always the people who don't exibit any of these signs even when they're going all-in with eight-high after the river.
* Standard Disclaimer: (In case you decide to gamble away your car, house, boat, life savings etc... and then want to blame me) This site is maintained by me and all tips, odds and articles are only my opinion and are not guaranteed to be accurate. Poker is gambling and you make your own desicions as to how to play the game regardless of what you read here or anywhere else and you are responsible for checking your own facts before getting in over your head. Gamble at your own risk ... You have been warned.