As Lisa drove home, she was suddenly alerted to the sound of a blaring horn and realized she had drifted off to sleep. Which nervous system division dominated when she was startled awake?

sympathetic nervous system

Explanation:

Sympathetic nervous system -

It is also known as the involuntary nervous system.

The sympathetic nervous system is responsible to direct the involuntary action of the body in any stressful and dangerous situation.

The process like,

The unconscious alteration of the blood pressure, heart rate, sweating, digestion etc., all falls under the sympathetic nervous system.

Hence, from the given scenario of the question,

The correct answer is sympathetic nervous system.