The part of the autonomic division of the nervous system that acts to prepare the body for action in stressful situations, engaging all the organism's resources to respond to a threat is known as the:

The sympathetic division.

Explanation:

There are two divisions of the autonomic nervous system. The sympathetic division is one of them. The sympathetic division works to prepare the body in stressful emergencies by engaging all the organism's resources so that they can respond to a threat. Another division of the autonomic nervous system is the parasympathetic division. It directs the body to store energy for use in emergencies.