Final answer:
The alarm reaction in the General Adaptation Syndrome activates the sympathetic nervous system, which drives the fight-or-flight response to stress.
Step-by-step explanation:
The first step in the alarm reaction to stress within the General Adaptation Syndrome involves the activation of the sympathetic nervous system. This system is responsible for what's typically known as the fight-or-flight response during stressful situations. During the alarm reaction stage of stress, the body is alerted to a stressor, prompting a cascade of physiological reactions that provide the energy to manage the situation. This includes the release of hormones such as epinephrine and norepinephrine from the adrenal medulla, which prepares the body for extreme physical exertion.
It's important to differentiate between the sympathetic and parasympathetic nervous systems. The sympathetic nervous system is activated during stressful "fight-or-flight" situations, while the parasympathetic nervous system resets organ function after such reactions, allowing the body to "rest and digest". The central nervous system, comprising the brain and spinal cord, controls and integrates all bodily functions, but it is the autonomic subdivision of the peripheral nervous system—particularly the sympathetic division—that is directly involved in the immediate stress response.