Adrenal Gland
அட்ரீனல் சுரப்பி
Adrenaline is the 'fight or flight' hormone and it boosts glycogen breakdown; aldosterone handles salt and water, not sugar. When NEET asks which hormone is NOT involved in sugar metabolism, the answer is aldosterone.
The idea
Our body has one pair of adrenal glands, one at the anterior part of each kidney. The gland is composed of two types of tissues — the centrally located tissue called the adrenal medulla, and outside this the adrenal cortex. The adrenal medulla secretes two hormones called adrenaline or epinephrine and noradrenaline or norepinephrine, commonly called catecholamines. Adrenaline and noradrenaline are rapidly secreted in response to stress of any kind and during emergency situations, and are called emergency hormones or hormones of fight or flight. These hormones increase alertness, pupillary dilation, piloerection (raising of hairs) and sweating; both increase the heartbeat, the strength of heart contraction and the rate of respiration. Catecholamines also stimulate the breakdown of glycogen, resulting in an increased concentration of glucose in blood; in addition they stimulate the breakdown of lipids and proteins. The adrenal cortex can be divided into three layers — zona reticularis (inner layer), zona fasciculata (middle layer) and zona glomerulosa (outer layer). The adrenal cortex secretes many hormones, commonly called corticoids. The corticoids involved in carbohydrate metabolism are called glucocorticoids; in our body, cortisol is the main glucocorticoid. Corticoids which regulate the balance of water and electrolytes in our body are called mineralocorticoids; aldosterone is the main mineralocorticoid. Glucocorticoids stimulate gluconeogenesis, lipolysis and proteolysis and inhibit cellular uptake and utilisation of amino acids. Cortisol is also involved in maintaining the cardiovascular system as well as kidney functions; glucocorticoids, particularly cortisol, produce anti-inflammatory reactions and suppress the immune response, and cortisol stimulates RBC production. Aldosterone acts mainly at the renal tubules and stimulates the reabsorption of Na+ and water and excretion of K+ and phosphate ions; it thus helps in the maintenance of electrolytes, body fluid volume, osmotic pressure and blood pressure. Small amounts of androgenic steroids are also secreted by the adrenal cortex, which play a role in the growth of axial hair, pubic hair and facial hair during puberty. Underproduction of hormones by the adrenal cortex alters carbohydrate metabolism, causing acute weakness and fatigue, leading to a disease called Addison's disease.
Why it matters
The adrenal medulla prepares the body for sudden danger within seconds, while the cortex manages longer-term stress, blood sugar and salt-water balance.
NEET lens
Medulla: adrenaline and noradrenaline (catecholamines; amino-acid derived) — emergency/fight-or-flight hormones; ↑ alertness, pupil dilation, piloerection, sweating, heartbeat, respiration; stimulate glycogenolysis (stress hormone that raises blood glucose). Cortex: three zones (reticularis inner, fasciculata middle, glomerulosa outer); cortisol (glucocorticoid — gluconeogenesis, anti-inflammatory, immunosuppressive, RBC production); aldosterone (mineralocorticoid — Na+ and water reabsorption, K+ and phosphate excretion); small androgens. Addison's disease = adrenal cortex underproduction. Aldosterone is NOT involved in sugar metabolism.
Clinical significance
Cortisol-like steroid drugs are widely used to reduce inflammation in asthma, arthritis and allergies, but long-term use suppresses immunity and raises blood sugar. Adrenaline injections are life-saving in severe allergic reactions (anaphylaxis).
Introduction
Each adrenal gland sits on top of a kidney and has an inner medulla (emergency hormones) and an outer cortex (corticoids).
Core concept
Adrenal medulla: adrenaline (epinephrine), noradrenaline (norepinephrine) = catecholamines; emergency / fight-or-flight hormones; ↑ alertness, pupillary dilation, piloerection, sweating, heartbeat, strength of heart contraction, respiration rate; ↑ glycogen breakdown → ↑ blood glucose; ↑ breakdown of lipids and proteins. Adrenal cortex: zona reticularis (inner), zona fasciculata (middle), zona glomerulosa (outer); corticoids. Glucocorticoids (main: cortisol): gluconeogenesis, lipolysis, proteolysis; inhibit cellular uptake/utilisation of amino acids; maintain cardiovascular and kidney functions; anti-inflammatory; suppress immune response; stimulate RBC production. Mineralocorticoids (main: aldosterone): renal tubules — reabsorption of Na+ and water, excretion of K+ and phosphate → electrolytes, body fluid volume, osmotic pressure, BP. Androgenic steroids: axial, pubic, facial hair at puberty. Underproduction → Addison's disease (acute weakness, fatigue).
Go deeper
Epinephrine is an amino-acid (tyrosine) derived hormone, whereas estradiol, estriol and ecdysone are steroids.
From Class 10
Class 10 introduced adrenaline as the hormone that prepares the body for emergencies. NEET adds the cortex and its two families of steroid hormones.