6.2.5 Adrenal Glands

The adrenal glands are two small endocrine glands located on top of each kidney. Each adrenal gland is composed of an inner portion called the medulla and an outer portion called the cortex. These two regions secrete different hormones that help the body respond to stress and regulate metabolism, salt balance, and other functions.

Definition

Adrenal Glands: Each of the two adrenal glands rests on a kidney. Each adrenal gland is composed of an inner portion called the medulla and outer portion the cortex.

Main Idea

• Each of the two adrenal glands rests on a kidney.
• Each adrenal gland has two parts:
• The adrenal medulla secretes epinephrine (adrenaline) and norepinephrine.
• The adrenal cortex secretes glucocorticoids (e.g., cortisone), mineralocorticoids (e.g., aldosterone), and androgens.
• Adrenal hormones help the body respond to stress and regulate metabolism, salt balance, and other functions.

Core Concept

• Adrenal glands = on top of kidneys
• Adrenal medulla = inner portion
• Adrenal cortex = outer portion
• Adrenal medulla hormones = epinephrine, norepinephrine
• Adrenal cortex hormones = glucocorticoids, mineralocorticoids, androgens
• Epinephrine and norepinephrine = fight or flight response
• Cortisone = regulates blood glucose
• Aldosterone = regulates salt and water balance
• Addison's disease = under secretion of cortical hormones
• Cushing's disease = over secretion of cortical hormones

Detailed Explanation

Adrenal Glands

• Each of the two adrenal glands rests on a kidney.
• Each adrenal gland is composed of an inner portion called the medulla and outer portion the cortex.

Adrenal Medulla

• Epinephrine (adrenaline) and norepinephrine are produced by the adrenal medulla.
• Both are released during the state of emergency under the influence of sympathetic nervous system.
• Both are involved in the body's immediate response to stress.
• The two hormones exert the same effects in different ways i.e., synergistic effect.
• Epinephrine is the more potent stimulator of metabolic activities, bronchial dilation and increased blood flow to skeletal muscles and the heart.
• Norepinephrine has the greater influence on peripheral vasoconstriction.
• The net effect is the rise in blood pressure.
• Over secretion of these hormones may cause hypertension and aggressive behaviour during routine life.
• Under secretion causes failure to combat with emergency situation.

Adrenal Cortex

• The two major types of hormones produced by the adrenal cortex are:
• Both are produced under the influence of ACTH.
• Androgen (testosterone) is also produced from adrenal cortex in small amount in both male and female bodies.
• Its major site of secretion are testes, which are male gonads.

• Leads to Addison's disease.
• Characterized by general metabolic disturbance, in particular, weakness of muscle action and loss of salts.
• Stress situation, such as cold which may lead to collapse and death.

• Causes Cushing's disease.
• Characterized by excessive protein breakdown resulting muscular and bone weakness.

Summary Table of Adrenal Gland Hormones

Disorders of Adrenal Gland

Intermediate Level

Adrenal Gland Hormones

Effects of Epinephrine and Norepinephrine

Effects of Cortical Hormones

Disorders of Adrenal Gland

Formula / Mathematical Form

Not applicable to this topic.

Solved Example

Not applicable to this topic (descriptive topic).

Important Points

• 1. Adrenal glands rest on top of each kidney.
• 2. Each adrenal gland has two parts: medulla and cortex.
• 3. Adrenal medulla is the inner portion.
• 4. Adrenal cortex is the outer portion.
• 5. Adrenal medulla secretes epinephrine and norepinephrine.
• 6. Adrenal cortex secretes glucocorticoids, mineralocorticoids, and androgens.
• 7. Epinephrine and norepinephrine are released during emergency.
• 8. They are under the influence of sympathetic nervous system.
• 9. They are involved in the body's immediate response to stress.
• 10. They have a synergistic effect.
• 11. Epinephrine is more potent for metabolic activities and bronchial dilation.
• 12. Norepinephrine has greater influence on peripheral vasoconstriction.
• 13. Net effect is rise in blood pressure.
• 14. Over secretion causes hypertension and aggressive behaviour.
• 15. Under secretion causes failure to combat emergency.
• 16. Cortisone regulates blood glucose.
• 17. Aldosterone regulates salt and water balance.
• 18. Androgens are produced in small amounts.
• 19. Under secretion of cortical hormones causes Addison's disease.
• 20. Over secretion of cortical hormones causes Cushing's disease.

Remember

• - Adrenal glands = on top of kidneys
• - Adrenal medulla = inner portion
• - Adrenal cortex = outer portion
• - Adrenal medulla hormones = epinephrine, norepinephrine
• - Adrenal cortex hormones = glucocorticoids, mineralocorticoids, androgens
• - Epinephrine and norepinephrine = fight or flight response
• - Cortisone = regulates blood glucose
• - Aldosterone = regulates salt and water balance
• - Addison's disease = under secretion of cortical hormones
• - Cushing's disease = over secretion of cortical hormones

Common Mistakes

• 1. Confusing adrenal medulla and cortex — Medulla = inner; cortex = outer.
• 2. Mixing up the hormones — Medulla: epinephrine, norepinephrine; cortex: cortisone, aldosterone, androgens.
• 3. Forgetting the role of the sympathetic nervous system — It stimulates the adrenal medulla.
• 4. Confusing epinephrine and norepinephrine — Epinephrine = metabolic activities; norepinephrine = vasoconstriction.
• 5. Mixing up Addison's and Cushing's diseases — Addison's = under secretion; Cushing's = over secretion.
• 6. Forgetting the role of ACTH — It stimulates the adrenal cortex.
• 7. Thinking aldosterone regulates blood glucose — Aldosterone regulates salt and water balance.
• 8. Believing androgens are only produced in males — Androgens are produced in both males and females.
• 9. Mixing up the effects — Epinephrine and norepinephrine raise blood pressure.
• 10. Confusing the disorders — Addison's disease: muscle weakness, loss of salts; Cushing's disease: protein breakdown, bone weakness.

Quick Revision

Each of the two adrenal glands rests on a kidney. Each adrenal gland is composed of an inner portion called the medulla and outer portion the cortex. Epinephrine (adrenaline) and norepinephrine are produced by the adrenal medulla. Both are released during the state of emergency under the influence of sympathetic nervous system. Both are involved in the body's immediate response to stress. The two hormones exert the same effects in different ways i.e., synergistic effect. Epinephrine is the more potent stimulator of metabolic activities, bronchial dilation and increased blood flow to skeletal muscles and the heart but norepinephrine has the greater influence on peripheral vasoconstriction. The net effect is the rise in blood pressure. Over secretion of these hormones may cause hypertension and aggressive behaviour during routine life. Under secretion causes failure to combat with emergency situation. The two major types of hormones produced by the adrenal cortex are glucocorticoids, e.g., cortisone, which help to regulate the blood glucose level and mineralocorticoids, e.g., aldosterone, which help to regulate the level of minerals in the blood. Both are produced under the influence of ACTH. Under secretion of cortical hormones will lead to Addison's disease which is characterized by general metabolic disturbance, in particular, weakness of muscle action and loss of salts. Over secretion of cortical hormone cause Cushing's disease which is characterized by excessive protein breakdown resulting muscular and bone weakness.

60-Second Revision

• Adrenal glands = on top of kidneys
• Adrenal medulla = inner portion
• Adrenal cortex = outer portion
• Adrenal medulla hormones = epinephrine, norepinephrine
• Adrenal cortex hormones = glucocorticoids, mineralocorticoids, androgens
• Epinephrine and norepinephrine = fight or flight response
• Cortisone = regulates blood glucose
• Aldosterone = regulates salt and water balance
• Addison's disease = under secretion of cortical hormones
• Cushing's disease = over secretion of cortical hormones
• Warning: Addison's disease = under secretion; Cushing's disease = over secretion

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• Chapter:
• 6. Endocrine System of Man

• Topic:
• 6.2.6 GONADS

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