Adrenal physiology

Question 1

What are the different layers of the adrenal cortex?

Answer 1

Zona glomerulosa - Mineralocortcoids, aldosterone, SALT
Zona fasciculata - Glucorticoids, cortisol, STRESS
Zona reticularis - androgens, SEX hormones

Medulla - ad

Question 2

Corticosteroids

Answer 2

• Lipid soluble
• Bind to specific intracellular receptors
• Alter gene transcription directly or indirectly
• Exact action depends on structure, ability to bind to specific receptors (and recruit cofactors)

Question 3

How does ACTH affect corticoids?

Answer 3

Adrenocorticotropic hormone binds to receptors on cell membrane, producing cAMP and the synthesis of corticosteroids

deficiency - adrenal shrinks
ACTH excess - grows

Question 4

Glucocorticoids

Answer 4

-Zone fasciculata and retiularis
-STRESS
effects = increase glucose mobilisation, vascular tone, salt and water balance, dampens immune system

Question 5

Describe the transport of Glucocorticoids in the body

-how does inflammation affect cortisol levels

Answer 5

90% bound to corticosteroid-binding globulin (CBG)

• 5% bound to albumin
• 5% free (these are the only ones that are available)

-inflammation lowers levels of CBG, so less is bound and there is a higher % of free cortisol

Question 6

How is glucocorticoid synthesis regulated?

Answer 6

1. Stress, cytokines and diurnal rhythm affect the hypothalamus
2. Affects levels of Corticotropin-releasing hormone released
3. Affects pituitary levels and levels of Adrenocorticotropic hormone released
4. ACTH - stimulates cortisol release and synthesis
5. Affects adrenal to secrete glucocorticoids :)
6. Affect on tissue

Question 7

What can cause stress?

Answer 7

“the sum of bodies responses to adverse stimuli”

• infection
• trauma
• haemorrhage
• medical illness
• psychological
• exercise/exhaustion

Question 8

Mineralocorticoids

Answer 8

• Synthesised in zona glomerulosa (contains aldosterone synthase)
• Mainly aldosterone and DOC
• Critical to salt and water balance

Question 9

Where does aldosterone affect?

Answer 9

• Affects distal tubule
• Increases Na+ resorption, more ENaC (epithelial sodium channel)
• Decreased excretion

Question 10

What is the juxtaglomerular apparatus?

Answer 10

1. the macula densa, a part of the distal convoluted tubule of the same nephron (senses plasma pressure)
2. juxtaglomerular cells, which secrete renin
3. extraglomerular mesangial cells

-it lies next to (juxta) to the glomerulus

Question 11

Describe the action of mineralocorticoids

Answer 11

• RAAS
• effects on pancreas
• sweat glands
• salivary glands
• colon

=increase sodium resorption

Question 12

Adrenal androgens

Answer 12

• Weak androgens generated in adrenal gland
• Dehydroepiandrosterone (DHEA) is the most abudent adrenal steroid but very weak
• Androstenedione - more androgenic but much weaker than testosterone
• ostrogen
• testosterone

Question 13

The adrenal medulla

Answer 13

• Autonomic system
• ACH transmitter
• Specialised ganglia - sympathetic
• Synthesises catecholamines (F & F)
• ADRENALINE AND NORADREALINE (v. low dopamine)

Question 14

What is the effect of catecholamines

Answer 14

• F&F - from the adrenal medulla
• increased gluconeogensis in liver and muscle
• lipolysis in adipose tissue
• tachycardia and cardiac contractility
• redistribution of circulating volume