According to the general adaptation syndrome, when a body first reacts to a stressor during the alarm stage, the body activates the system, causing increase in heart rate, blood pressure, and supply of blood sugar.

Sympathetic nervous.

Explanation:

The human nervous system is divided into the autonomic nervous system and peripheral nervous system. The autonomic nervous system controls all the involuntary actions of the body.

The autonomic nervous system is divided into sympathetic nervous system and para sympathetic nervous system. The sympathetic nervous system activates at the fight and flight condition of the body. This system increase  the blood pressure, increases heart beat that helps to cope with the stress condition of the body.

Thus, the answer is sympathetic nervous.