The heart speeds up, from 10 to 20 beats per minute
The blood vessels constrict, or tighten, so that blood pressure goes up 5 to 10 points.
The temperature of the skin drops by 6 degrees Fahrenheit (that's because the blood is rushing to the heart, where it would be needed in a real crisis)
The level of blood sugar, the body's store of energy, falls, because the blood sugar is being burned up in a stressed out reaction.
The hypothalamus, which regulates hunger, gets a “speed-up” message, so the appetite falls too.