Lecture 31

Question 1

Describe the anatomical structure of the adrenal gland:

Answer 1

The adrenal glands are located on the top of the kidney. The outer cortex accounts for 80% of the mass, while the inner portion contributed to 20% of the mass.

Question 2

State the order of the adrenal gland tissues from the outermost to the inner:

Answer 2

Zona glomerulosa (thinnest and outermost) then the zona fasciculata (middle and thickest) and the zona reticularis is the inner most

Question 3

What is secreted by the zona glomerulosa?

Answer 3

mineralocorticoids (aldosterone)

Question 4

What is secreted by the zona fasciculata and the zona reticularis?

Answer 4

glucocorticoids (cortisol) and sex steroids (androgens)

Question 5

What are the steps involved in the process of glucocorticoid hormone synthesis?

Answer 5

1. Low density lipoproteins in the blood account for the majority of the cholesterol that reaches the adrenal glands
2. The low density lipoproteins complex is then endodigested into a lysosome
3. Transferred to the inner mitochondrial membrane by StAR proteins (this is the rate limiting step)
4. Converted to pregnenolone by cytochrome 450scc enzyme
5. Undergoes complex conversion to a wide variety of different hormones

Question 6

How is the release of mineralocorticoids and glucocorticoids mediated?

Answer 6

Cortico-tropic releasing hormone is released from the hypothalamus and controls the release of ACTH in the process stimulating glucocorticoid synthesis

Question 7

What are the factors that regulate glucocorticoid secretion?

Answer 7

• Circadian rhythms are highest on waking and then decline throughout the day
• Stressors- physical stressors including hypoglycaemia and pro-inflammatoy cytokines
• Negative feedback- mechanisms include circulating glucocorticoids

Question 8

What are the main actions of glucocorticoid hormones?

Answer 8

• These are catabolic raising blood glucose through the mobilisation of carbohydrates, lipids and proteins particularly in periods of stress
• The glucocorticoid hormones also have a negative impact upon calcium within our body enhancing the excretion of calcium as we begin to mobilise calcium from our bones
• Anti-inflammatory effect within the body stabilising lysosomal membranes and inhibiting the release of lysosomal enzyme activity and in the process restricting damage to adjacent healthy cells

Question 9

What are the major biological actions of mineralocorticoids within the body?

Answer 9

• Binds to the receptors in the cytosol of the principle cell and late collecting ducts. Increases the amount of sodium and potassium channels on the apical membrane. This also causes the synthesis of sodium/potassium channels on the basolateral membrane. This allows for simultaneous increasing of sodium re-absorption and potassium secretion.

Question 10

What is the main factor influencing the release of aldosterone?

Answer 10

Angiotensin-II

Question 11

Where is epinephrine made?

Answer 11

In the renal medulla

Question 12

Where is norepinephrine synthesised?

Answer 12

made within the renal medulla and in the peripheral sympathetic nerves

Question 13

Describe how caetochotlamines are synthesized within the medulla:

Answer 13

1. Tyrosine is ingested or synthesised from phenylalanine in liver
2. Then moved into the renal medulla
3. Tyrosine hydroxylase is the rate limiting step within this reaction

Question 14

How is Epinephrine released?

Answer 14

direct stimulation of the adrenal gland

Question 15

How is norepinephrine released?

Answer 15

adrenergic receptor stimulation

Question 16

What is the role of epinephrine and nor-epinephrine is stress?

Answer 16

Epinephrine acts to increase blood pressure, reduce gut motility, bronchodilation and