Reflex

Any response you have to a stimulus that is inherent (you are born with it), it is a reflex. You are probably familiar with physical reflexes such as when the doctor hits your knee with that mallet to test the knee-jerk reflex. Another example is when you put your hand too close to the hot stove and have that reaction of yanking it away from the pain. You don't need to think about it, but the message from your hand to the brain and then back again makes it happen automatically.