The Adrenals and their Hormones

Question 1

What are the parts of the adrenal gland from the outside to the inside?

Answer 1

Zona Glomerulosa (aldosterone production) Zona Fasciculata (cortisol and sex steroids) Zona Reticularis (cortisol and sex steroids) Adrenal Medulla

Question 2

What is the direction of blood flow in the adrenals?

Answer 2

From the cortex towards the medulla (most however go through the cells)

Question 3

What is produced by the adrenal medulla? What are the cells involved called?

Answer 3

Catecholamines by the Chromaffin cells ( catecholamines are NOT associated with chromaffin cells)

Question 4

What is produced in the adrenal cortex? State the four hormones produced.

Answer 4

• Corticosteroids: Mineralocorticoids - aldosterone + Glucocorticoids - cortisol
• Sex Steroids - androgens and oestrogens

Question 5

What is androstenedione?

Answer 5

It is a weak androgen that can be converted to testosterone and dihydrotestosterone

Question 6

How are corticosteroids transported in the blood?

Answer 6

They bind to plasma proteins. There is so much albumin that some corticosteroids will non-specifically bind to albumin. There are more specific plasma proteins - corticosteroid binding globulin

Question 7

Describe the difference in the blood concentrations of cortisol and aldosterone.

Answer 7

The concentration of cortisol is 1000 times greater than the concentration of aldosterone.

Question 8

How does cortisol concentration vary?

Answer 8

Cortisol concentration changes with the circadian rhythm. It is a stress hormone so is released more at times of stress.

Question 9

What are the effects of aldosterone?

Answer 9

Increased potassium and H+ secretion Increase sodium reabsorption

Question 10

Describe the mechanism of action of aldosterone.

Answer 10

1. Passes through membrane and binds to intracellular receptors.
2. RHC moves to nucleus and acts as a transcription factor and binds to DNA.
3. Proteins produced are enzymes/pumps.
   a. proteins may stimulate ATPase on basolateral membrane to pump Na+ into blood
   b. Stimulates synthesis if ion channels eg Na+ channels in apical membrane

Question 11

Describe the arrangement of the juxta-glomerular apparatus in the kidneys.

Answer 11

The juxta-glomerular cells are in contact with the afferent arteriole. The macula densa cells are next to the juxta-glomerular cells and are in the DCT.

Question 12

What hormone is stimulated by an increase in plasma osmolality?

Answer 12

Vasopressin

Question 13

What is a consequence of increase extracellular fluid volume?

Answer 13

Hypertension

Question 14

Describe how the juxtaglomerular apparatus can lead to production of aldosterone.

Answer 14

1. Liver produces angiotensinogen
2. Renin breaks angiotensinogen to angiotensin I
3. ACE ( angiotensin converting enzyme) converts angiotensin I to angiotensin II
4. Angiotensin II stimulates zona glomerulosa to produce aldosterone

Question 15

State three causes of renin release.

Answer 15

1. Decreased renal perfusion pressure
2. Increased renal sympathetic activity
3. Decreased sodium concentration at the top of the loop of Henle

Question 16

Describe the steps in the production of angiotensin II from the angiotensinogen.

Answer 16

Renin converts angiotensinogen (produced by the liver) to angiotensin I Angiotensin I is converted by ACE (which is found in high concentration in the lung endothelium) to Angiotensin II

Question 17

What are the effects of cortisol?

Answer 17

• Increased hepatic gluconeogenesis
• Increase glycogenolysis Increased fat metabolism
• Stimulates peripheral protein catabolism
• Enhances effects of glucagon and catecholamines

Question 18

What are the three effects of large amounts of cortisol?

Answer 18

Anti-inflammatory Immunosuppressive Anti-allergic

Question 19

Which receptors do a) aldosterone and b) cortisol bind to?

Answer 19

Aldosterone - mineralocorticoid receptors Cortisol - glucocorticoid receptors AND mineralocorticoid receptors

Question 20

Describe the mechanism of action of cortisol.

Answer 20

Cortisol binds to intracellular receptors, moves to the nucleus and causes a GENOMIC change.

For example, annexin 1 which has an autocrin effect and binds. Annexin 1 receptor on same cell. This stimulates phospholipase which works on phospholipids to increase arachidonic acid. Cortisol blocks the production of arachidonic acid thereby decreasing prostaglandin synthesis.

Question 21

Describe the control of cortisol.

Answer 21

There is direct negative feedback by ACTH on the hypothalamus Cortisol also have negative feedback effects on the hypothalamus and on the adenohypophysis

Question 22

What is dehydroepiandrosterone (DHEA)?

Answer 22

This is a very weak androgen that peaks around 20-30 years. It is particularly important in post-menopausal women as a precursor for oestrogen.

Question 23

As cortisol has a much higher blood concentration than aldosterone, why doesn’t cortisol constantly bind to mineralocorticoid receptors?

Answer 23

The kidneys have an enzyme called 11 beta-hydroxysteroid dehydrogenase 2 that converts cortisol into the inactive CORTISONE.

Question 24

Where is each of the corticosteroids made?

Answer 24

Aldosterone - Zona glomerulosa Cortisol - Zona fasciculata and reticularis Sex steroids - Zona fasciculata and reticularis

Question 25

What are all corticosteroids derived from?

Answer 25

cholesterol

Question 26

What hormones are made in the adrenal medulla?

Answer 26

Adrenaline - 80% Noradrenaline - 20% Dopamine - very small amounts

Question 27

Whats the precursor for aldosterone?

Answer 27

progesterone

Question 28

What is the precursor for oestrogens?

Answer 28

androgens

Question 29

Draw the structure of the adrenal gland

Answer 29

Question 30

Contrast how Aldoesterone and cortisol are carried in blood

Answer 30

Aldosterone:

• 40% - Free Hormone
• 15% - CBG
• 45% - Albumin

Cortisol:

• 10% - Free Hormone
• 80% - CBG
• 10% - Albumin