Endocrine Physiology - The Adrenal Gland

Question 1

The adrenal gland is composed of two quite seperate endocrine glands roled into one structure:

Answer 1

• Adrenal cortex (75%) - a true endocrine gland
• Adrenal medulla (25%) - a modified sympathetic ganglion

Question 2

What does the adrenal medulla secrete?

Answer 2

Catecholamines - mainly epinephrine but also norepinephrine and dopamine.

Question 3

What are the three layers of the adrenal cortex and what do they secrete? (From superficial to deep.)

Answer 3

• Zona glomerulosa → Aldosterone
• Zona fasciculata → Glucocorticoids
• Zona reticularis → Sex steroids

Question 4

Actions of cortisol on glucose metabolism.

Answer 4

• Gluconeogenesis - cortisol stimulates the formation of gouconeogenic enzymes in the liver
• Proteolysis - coritsol stimulates the breakdown of muscle protein, creating a substrate for gluconeogenesis
• Lipolysis - provides and alternative fuel supply thath allows [BG] to be protected while also creating a substrate for gluconeogenesis
• Decreases the insulin sensitivity of muscles and adipose tissue

Question 5

How does cortisol affect [Ca2+]?

Answer 5

↓plama [Ca2+]

Inhibits osteoblasts, increases renal excretion of Ca2+ and phosphate and reduces intestinal absorption of Ca2+.

Excess cortisol can, over time, result in osteoporosis.

Question 6

How does cortisol affect mood and cogntions?

Answer 6

Depression and impairment of cognitive function are stongly associated with hypercortisolaemia.

Question 7

How does cortisol affect blood pressure?

Answer 7

Cortisol has permissive effects on norepinephrine - particularly in vascular smooth muscle (alpha receptor effect = vasoconstrictive.) Cushing’s disease is strongly associated with hypertension.

Question 8

How does cortisol affect the immune system?

Answer 8

Cortisol supresses the immune system - reduces circulating lymphocyte count, reduces antibody formation and inhibits the inflamatory respone.

Question 9

Describe the hypothalamic pituitary adrenal pathway leading to cortisol release.

Answer 9

Hypothalamus

↓

CRH

↓

Anterior Pituitary

↓

ACTH

↓

Adrenal Cortex

↓

Cortisol release

Question 10

What is the action of aldosterone?

Answer 10

Aldosteone increased the renal reabsorption of Na+ ions and promotes the excretion of K+ ions.

This results in increased blood volume and blood pressure.

Question 11

How is secretion fo aldosterone by the adrenal cortex controlled?

Answer 11

The renin-angiotensin-aldosterone system (RAAS)