What immediate response is triggered by the autonomic nervous system when a person is stressed?

When a person is stressed, the autonomic nervous system activates the fight-or-flight response. This physiological reaction prepares the body to either confront or flee from a perceived threat. During this response, various changes occur: the heart rate increases, blood pressure rises, and adrenaline is released, which enhances alertness and energizes the body. These changes are crucial for survival in dangerous situations, as they optimize physical performance and mental focus.

The other responses do not align with the body's immediate reaction to stress. The relaxation response and rest and digest response are associated with a calm state, promoting recovery and digestion, which occurs when the body is not under stress. The sleep promotion response is also not activated in stressful situations; instead, stress generally inhibits sleep by stimulating arousal systems in the body. Thus, the fight-or-flight response is the correct answer, as it is the body’s instinctive reaction to a stressor.