Topic: Endocrinology (Stress Hormones)
The "fight or flight" response is an evolutionary survival mechanism that prepares the body to either stay and deal with a threat or run away to safety.
Steps:
Understanding the Question: Which hormone is released almost instantly by the adrenal glands to increase heart rate and energy during a sudden crisis?
Key Formulas and Approach: Differentiate between acute stress (instant) and chronic stress (long-term).
Detailed Solution:
Adrenaline (Epinephrine) is secreted by the adrenal medulla in response to acute stress.
It causes immediate physiological changes: increased heart rate, dilation of pupils, and mobilization of glucose for energy.
While Cortisol is also a stress hormone, it is involved in long-term stress regulation rather than the immediate "fight or flight" burst.