Q.Which hormone, secreted by the adrenal medulla and often called the 'emergency hormone', raises heart rate, blood pressure and blood glucose during a fight-or-flight response?

The adrenal cortex has three concentric zones — zona glomerulosa, zona fasciculata and zona reticularis — each responsible for secreting a different category of steroid hormone.

Each adrenal gland (situated atop each kidney) has an outer cortex and an inner medulla. The adrenal cortex itself is organised into three histologically and functionally distinct layers, arranged from the outer surface inward:

1. Zona glomerulosa (outermost layer): made of cells arranged in rounded clusters; secretes mineralocorticoids, chiefly aldosterone, which regulates sodium and potassium balance and blood pressure.

2. Zona fasciculata (middle layer, the thickest of the three): made of cells arranged in long, straight cords; secretes glucocorticoids, chiefly cortisol, which regulates glucose metabolism and the body's response to stress.

3. Zona reticularis (innermost layer): made of cells arranged in an irregular, net-like pattern; secretes small amounts of gonadocorticoids (sex steroids, mainly androgens such as DHEA).

Adrenaline is nicknamed the '3F hormone' because it is released during stress to prime the body for Fight, Flight, or Fright, the classic emergency stress response.

Adrenaline (epinephrine) is a hormone secreted by the adrenal medulla (the inner part of the adrenal gland) in response to stress, fear, excitement, or any perceived emergency/danger. It is called the '3F hormone' because it readies the body to respond in one of the three classic ways an animal reacts to a threatening situation: Fight (confronting the danger), Flight (fleeing from the danger), or Fright (freezing in response to sudden danger). To prepare the body for whichever of these responses is needed, adrenaline produces a rapid set of physiological changes: it increases heart rate and the force of heart contraction, raises blood pressure, dilates the pupils (for better vision), dilates the bronchioles in the lungs (for more oxygen intake), increases blood glucose levels by promoting glycogen breakdown in the liver (providing quick energy to muscles), and redirects blood flow away from non-essential organs (like the digestive system) toward the skeletal muscles, heart, and brain — all changes suited to sudden intense physical action. Because this hormone is specifically tied to these fight-flight-fright reactions, it has earned the nickname the 3F hormone.

The adrenal cortex is organised into three concentric zones, each secreting a different class of steroid hormone.

Zones (outer to inner):

• Zona glomerulosa (outermost): secretes mineralocorticoids, chiefly aldosterone, which regulates reabsorption of sodium and excretion of potassium in the kidney tubules, controlling blood volume and pressure.
• Zona fasciculata (middle, thickest zone): secretes glucocorticoids, chiefly cortisol, which regulates carbohydrate, protein and lipid metabolism, has anti-inflammatory effects, and helps the body respond to stress.
• Zona reticularis (innermost): secretes small amounts of gonadocorticoids — mainly weak androgens (such as DHEA) and small quantities of other sex steroids, supplementing gonadal sex hormones.