Final Answer:
The major catecholamine released by the adrenal medulla is epinephrine, also known as adrenaline.
Step-by-step explanation:
The primary catecholamine released by the adrenal medulla is epinephrine, which is commonly referred to as adrenaline. This hormone plays a pivotal role in the body's "fight or flight" response, triggering various physiological changes to help the body respond to stress or danger.
When the body perceives a threat or stressor, the adrenal medulla, situated atop the kidneys, secretes epinephrine into the bloodstream. Epinephrine rapidly increases heart rate, elevates blood pressure, dilates air passages in the lungs, and shifts blood flow to essential organs like the heart and muscles.
These responses help prepare the body to either confront the danger or flee from it, enabling a swift and efficient response to stressful situations. As a crucial part of the sympathetic nervous system's response, epinephrine serves as a vital hormone facilitating immediate reactions in the face of challenges or emergencies, ensuring the body is primed for action.