Final answer:
The Limbic System, including structures like the amygdala and hippocampus, is the part of the brain that is primarily activated by traumatic stress.
Step-by-step explanation:
The part of the brain that is primarily activated by traumatic stress is the Limbic System. This brain region regulates emotions and behaviors related to fear and motivation. In particular, the amygdala, part of the limbic system, is known for its role in the sensation of fear and for recognizing fearful faces. Moreover, the limbic system includes the hippocampus, which plays a crucial role in memory formation.
Increased amygdala activity is associated with learning to fear and is seen in individuals at risk for, or suffering from, mood disorders. The limbic system's response to traumatic stress can lead to heightened alertness, anxiety, and impactful memories, evidencing its central role in emotional processing.