8 - The Adrenals and their hormones

Question 1

How many adrenal glands are there?

Answer 1

2 - left and right

Question 2

Where do the left and right adrenal glands drain into?

Answer 2

Left - Renal vein

Right - IVC

Question 3

What is the structure of the adrenal gland?

Draw it.

Answer 3

Middle = medulla
Cortex = 
Zona reticularis
Zona faciculata 
Zona glomerulosa

Question 4

What does the adrenal cortex produce?

Answer 4

Corticosteroids

-Mineralocorticoids (aldosterone
-Glucocorticoids (cortisol)
Sex steroids – mainly androgens, some oestrogen)

Question 5

What does the adrenal medulla produce?

Answer 5

Catecholamines

• Adrenaline (epinephrine; 80%)
• Noradrenaline (norepinephrine; 20%)
• Dopamine

Question 6

Where is aldosterone produced?

Answer 6

Zona glomerulosa (outer part of cortex)

Question 7

What type of hormones are produced by the adrenal glands?

Answer 7

Steroid hormones

Question 8

How is cortisol transported in the blood?

Answer 8

CORTISOL

75% bound to corticosteroid binding globulin (CBG, also known as transcortin)
15% bound to albumin
10% free (unbound) -> bioactive

Question 9

How is aldosterone transported in the blood?

Answer 9

ALDOSTERONE

60% bound to CBG
40% free (unbound) -> bioactive

Question 10

How are the adrenal glands supplied with blood?

Answer 10

Lots of arteries around the edge.

1 central vein that leaves from the middle of the medulla.

Question 11

Where in the adrenal cortex is cortisol (and some androgens & oestrogens) produced?

Answer 11

Zona reticular and zona glomerulosa.

Question 12

Why are different hormones produced in different zones of the adrenal cortex?

Answer 12

Different enzymes are present in different zones so synthesis will follow a different pathway.

Question 13

Why are steroid hormones found in the blood and not in cells?

Answer 13

They are very lipid soluble so can diffuse out of cells into blood easily.

Question 14

When is cortisol at its highest and lowest concentrations in the blood?

Answer 14

Highest = morning 140-690 nmol/L
Lowest = evening 80-330 nmol/L

Question 15

What is the aldosterone level of the blood?

Answer 15

140-560 pool/L (1000 times less than cortisol)

Question 16

What receptors can cortisol bind to?

Answer 16

Glucocorticoid Receptors (GR) 
AND
Aldosterone Receptors (MR - mineralocorticoid receptor)

Question 17

What receptors can aldosterone bind to?

Answer 17

ONLY
Aldosterone Receptors (MR - mineralocorticoid receptor)

Question 18

What is the name of the enzyme that breaks down cortisol making it inactive? What is the point of this and where is it found?

Answer 18

11b-hydroxysteroid dehydrogenase 2. (11b-HSD2).

It means aldosterone has to be used instead of cortisol.

Found in the kidneys and placenta.

Question 19

Where is renin produced?

Answer 19

Granular cells that line the afferent artery in the kidney.

Question 20

What 3 things cause renin to be produced?

Answer 20

1. Renal Perfusion Pressure DECREASE
   (BP in afferent arteriole)
2. Renal sympathetic nerves ACTIVATED
3. Macular dense cells in distal convoluted tubule detect LOW sodium concentration in the fluid in DCT.

Question 21

What does renin do?

Answer 21

• Increases sodium and water reabsorption in the kidney.

- Preserves blood pressure.

Question 22

Explain the renin-angiotensin-aldosterone system.

Answer 22

1. Renin (enzyme) released from kidney
2. Renin acts on angiotensinogen (protein from liver) making angiotensin I.
3. ACE (angiotensin converting enzyme) acts on angiotensin I making angiotensin II.
4. Angiotensin II stimulates aldosterone production in the zona glomerulosa.

Question 23

What 2 other things can stimulate aldosterone production?

Answer 23

• Low blood sodium

- High blood potassium

Question 24

How is cortisol produced?

Answer 24

1. CRH (corticotrophin releasing hormone) released from hypothalamus to anterior pituitary.
2. Corticotrophs in the anterior pituitary produce ACTH (adrenocorticotrophin) which goes to the adrenal cortex.
3. Cortisol is produced from the zona fasciculate and reticular in the adrenal cortex.

Negative feedback.

Question 25

What is the function of aldosterone?

Answer 25

Function is in the Distal tubule collecting duct.

Alters transcription & translation in cell.
Aldosterone increases the number of sodium channels and sodium potassium ATPases in distal tubule cells so more Na+ is reabsorbed from the fluid back into the blood.

= More water is also reabsorbed into the blood

Question 26

Normally - how does cortisol bind to MR and GR?

Answer 26

Heavily binded to MR

Partially binded to GR

Question 27

What is the function of cortisol (& in the liver)?

Answer 27

LIVER:
Increases gluconeogenesis and glycogenesis.
=more glucose and glycogen

Elsewhere (skeletal & adipose tissue)
Stops glucose and free fatty acids getting into muscle and fat cells. (Decreases GLUT4)
=more glucose in blood.

Question 28

What is the action of cortisol on memory?

What part of the brain is this in?

Answer 28

Memories are formed in the Dantete Gyrus.
Serotonin promotes new memory formation.
Cortisol increases the capacity to respond to serotonin = more serotonin receptors = more memories.
Particularly memories of stressful situations.

Question 29

What are the 2 other major actions of cortisol?

Answer 29

Anti-inflammatory

Immunosuppressive.

Question 30

What 2 things increase cortisol action?

Answer 30

Alcohol & caffeine

Question 31

When can cortisol have a negative effect on memories?

Answer 31

When it is bound to too much GR.
= negative effect on serotonin
= smaller hippocampus.