Darlene just found out that she made the dean's list, and she's in ecstasy -- singing and dancing down the hallway near her dorm room. which area of the brain is directing her emotional reaction?

The limbic system

Explanation:

The limbic system is responsible for emotional reaction and responses. It is a network of different parts of the brain:

Hypothalamus

Thalamus

Amygdala

Hippocampus

The limbic system also controls our behavioral reaction. It works to sort out pleasant and unpleasant states of mind. Depending on how it categorizes as situation, the limbic system will produce the hormones that trigger brain activity . The fluctuations in activity result in physical changes and reactions (like expressions, gestures, stance) in response to the situation.