Functions of Cortical and Medullary Hormones

Introduction

The adrenal glands play a crucial role in maintaining the body's internal balance (homeostasis) through the secretion of cortical and medullary hormones. These hormones help regulate stress responses, metabolism, blood pressure, and more. Understanding their distinct functions gives insight into how our body adapts to internal and external stimuli.

Diagram of adrenal gland showing cortex zones and medulla
 with their hormone secretions and physiological functions.

Structure of the Adrenal Gland

The adrenal gland consists of two major parts:

1. Adrenal Cortex – The outer region

2. Adrenal Medulla – The inner region

Each part secretes different hormones that serve specialized physiological functions.

Cortical Hormones and Their Functions

The adrenal cortex is further divided into three zones, each producing specific hormones:

1. Zona Glomerulosa – Produces Mineralocorticoids

Main Hormone: Aldosterone
Function:

1. Regulates sodium and potassium balance
2. Controls blood pressure by promoting reabsorption of sodium and excretion of potassium in the kidneys
3. Maintains water balance indirectly

2. Zona Fasciculata – Produces Glucocorticoids

Main Hormone: Cortisol
Function:

1. Increases blood glucose through gluconeogenesis
2. Suppresses immune response (anti-inflammatory effects)
3. Helps in metabolism of carbohydrates, fats, and proteins
4. Regulates stress response

3. Zona Reticularis – Produces Gonadocorticoids (Sex Hormones)

Main Hormones: Androgens (like DHEA)
Function: 

1. Supplement sex hormones from the gonads
2. Contribute to the development of secondary sexual characteristics 
3. Play a role in libido and muscle growth

Medullary Hormones and Their Functions

The adrenal medulla is composed of modified nerve cells and functions as part of the sympathetic nervous system.

Main Hormones: Epinephrine (Adrenaline) and Norepinephrine (Noradrenaline)

Functions of Medullary Hormones: 

1. Trigger the ‘fight-or-flight’ response during stress 
2. Increase heart rate and blood pressure
3. Dilate airways to enhance oxygen intake 
4. Mobilize energy by increasing glucose in the bloodstream
5. Divert blood flow to essential organs like the heart and muscles

FAQs

Q1: What happens if cortisol levels are too high?

A: High cortisol levels may lead to Cushing’s syndrome, causing weight gain, high blood pressure, and suppressed immunity.

Q2: Can adrenal medullary hormones affect mood?

A: Yes, excess adrenaline can cause anxiety, panic attacks, and sleep disturbances.

Q3: Are adrenal hormones the same in all animals?

A: While the general function is conserved, the structure and hormone levels vary among vertebrates.

Q4: What triggers adrenal hormone release?

A: Cortical hormones are stimulated by ACTH from the pituitary, while medullary hormones respond to nerve impulses during stress.

Q5: Is aldosterone related to dehydration?

A: Yes, aldosterone helps retain sodium and water, preventing dehydration.

References

1. Guyton, A. C., & Hall, J. E. (2016). Textbook of Medical Physiology (13th ed.). Elsevier.

2. Tortora, G. J., & Derrickson, B. H. (2014). Principles of Anatomy and Physiology (14th ed.). Wiley.

3. Sherwood, L. (2015). Human Physiology: From Cells to Systems (9th ed.). Cengage Learning.

4. Rastogi, S. C. (2015). Essentials of Animal Physiology. New Age International.