The Adrenals and their Hormones

Question 1

where is the adrenal gland located?

Answer 1

Embedded on the superior pole of each of the two kidney, they have their own capsules.
also called suprarenal glands.

Question 2

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

Answer 2

• Zona Glomerulosa (aldosterone production)
• Zona Fasciculata:line up as strings (cortisol and sex steroids)
• Zona Reticularis (cortisol and sex steroids)
• Cortex
• Adrenal Medulla

Question 3

What is the direction of blood flow in the adrenals?

Answer 3

From the cortex towards the medulla

Question 4

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

Answer 4

Catecholamines such as adrenaline, noradrenaline and dopamine by the Chromaffin cells

Question 5

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

Answer 5

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

Question 6

What is androstenedione?

Answer 6

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

Question 7

What are precursors of oestrogen and aldosterone

Answer 7

• progesterone is a precursor for aldosterone.

- androgens are precursors of oestrogens

Question 8

where are androgen produced and what is the difference

Answer 8

androgen is produced by the adrenal cortex and the testes, more powerful from the testes.

Question 9

How are corticosteroids transported in the blood and cortisol?

Answer 9

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, which majority of them bind to. and some are unbound which are bioactive
-Cortisol binds to the glucocorticoid receptor (GR)

Question 10

How are aldosterone transported in the blood?

Answer 10

• Most bound to corticosteroid binding globulin
• the rest are unbound: bioactive
• aldosterone binds to the mineralocorticoid receptor (MR).

Question 11

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

Answer 11

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

Question 12

How does cortisol concentration vary and aldosterone?

Answer 12

Cortisol concentration changes with the circadian rhythm. It is a stress hormone so is released more at times of stress.
-released in PULSES.
Aldosterone in NOT controlled by the pituitary gland so the time of day is NOT important- but the balance on fluid and balance.

Question 13

What are the effects of aldosterone?

Answer 13

Increased K+ and H+ secretion in the distal convoluted tubule and corticol collecting duct, therefore will effect on pH.
Increase sodium reabsorption, this is important in the kidneys but also in sweat glands, gastric glands and colon.

Question 14

Describe the mechanism of action of aldosterone.

Answer 14

• steroid so passes through cell membrane and binds to intracellular receptors.
• translocates to the nucleus and causes changes in transcription leading to the synthesis of ion channels and pumps.
• Aldosterone stimulates the synthesis of ion channels, in particular Na+ channel in the apical membrane

Question 15

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

Answer 15

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

Question 16

What hormone is stimulated by an increase in plasma osmolality?

Answer 16

Vasopressin

Question 17

What is a consequence of increase extracellular fluid volume?

Answer 17

Hypertension due to maintained expansion of extracellular fluid volume

Question 18

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

Answer 18

Macula densa detects a decrease in tubular sodium concentration and stimulates the release of renin from the juxta-glomerular cells. Renin stimulates the production of angiotensin II, which upregulates aldosterone release.

Question 19

State three causes of renin release.

Answer 19

Decreased renal perfusion pressure
Increased renal sympathetic activity
Decreased sodium concentration at the top of the loop of Henle

Question 20

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

Answer 20

Renin converts angiotensinogen (produced by the liver) to angiotensin I
Angiotensin I is converted by ACE: angiotensin converting enzyme (which is found in high concentration in the lung endothelium) to Angiotensin II which then stimulates zona glomerulus to produce aldosterone

Question 21

What are the effects of angiotensin II

Answer 21

Vasoconstrictor

Question 22

what are the other factors that affect aldosterone production?

Answer 22

-corticotrophin: it will enhance the renin angiotensin system.
-angiotensin regulates ions:
if blood plasma sodium ion falls, it has a direct effect in stimulating aldosterone production so there is more sodium reabsorption and sodium concentration returns to normal.
-aldosterone is also the main mechanism for regulating potassium

Question 23

What are the effects of cortisol?

Answer 23

Increased hepatic gluconeogenesis
Increase glycogenolysis
Increased fat metabolism
Stimulates peripheral protein catabolism
Enhances effects of glucagon and catecholamines
OVERALL: increase blood glucose concentration

Question 24

What are the three effects of large amounts of cortisol?

Answer 24

Anti-inflammatory
Immunosuppressive
Anti-allergic

Question 25

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

Answer 25

Aldosterone - mineralocorticoid receptors

Cortisol - glucocorticoid receptors AND mineralocorticoid receptors

Question 26

Describe the mechanism of action of cortisol.

Answer 26

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

Question 27

Describe the control of cortisol.

Answer 27

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

Question 28

What is dehydroepiandrosterone (DHEA)?

Answer 28

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 29

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

Answer 29

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