Which hormone is known for stimulating the sympathetic nervous system in response to physical injury or mental stress?

Adrenaline, also known as epinephrine, plays a crucial role in the body's response to stress, both physical and emotional. When the body perceives a threat—whether due to physical injury or mental stress—adrenaline is released from the adrenal glands into the bloodstream. This release triggers the "fight or flight" response, which prepares the body to react quickly to danger.

The action of adrenaline leads to several physiological changes: it increases heart rate, elevates blood pressure, dilates air passages, and boosts energy availability by increasing blood sugar levels. These changes enhance physical performance and readiness, allowing one to either confront the stressor or flee from it. This mechanism is critical for survival in emergencies and is a key characteristic of the sympathetic nervous system's activation.

In contrast, other hormones listed do not primarily stimulate the sympathetic nervous system in response to injury or stress. For instance, norepinephrine is also involved in the stress response, but it primarily functions as a neurotransmitter rather than a hormone released into the blood stream in the same manner as adrenaline. Serotonin is primarily associated with mood regulation and does not directly stimulate the sympathetic nervous system. Insulin's role is primarily in glucose metabolism and energy storage, making it less relevant