Answer to the question

Alli, here is our answer. I found this on discoverymagazine.com (a teacher site I send my students to!).

God has given His creatures the ability to do all sorts of things without even thinking about it. These are called reflexes, and they work by a special connection between nerves and muscles. Examples include the heart beat, blinking, focusing the eyes, swallowing, stepping, and scratching an itch. For instance, we might know when we blink because it goes dark for a split second. Sure, we can blink whenever we want to, but most of the time, we never notice it.

Because reflexes can work without the brain, you still can see movement in the body after the head has been cut off. This is what happened to the snake. Its reflexes worked as long as its nerve cells had oxygen. After your dad cut its head off, no new oxygen reached these cells, and the reflexes stopped.