Touching a hot pan and yanking your hand away: Pain and reflexes
Jumping up and down: Equilibrium and depth perception.
Drinking water on a hot day: Dehydration and lowering your temperature.
Sneezing: reaction to dust, smut, grains, or allergies.
Blushing: The rising of your blood temperature and nervousness.
Hitting your head on the top of the car as you get into it: Pain and depth perception.
Breathing harder during a jog: increased heart rate, blood flow, and less oxygen.