The Adrenal Gland

Question 1

What are the two seperate endocrine glands that makes up the adrenal gland?

Answer 1

Adrenal medulla (Neuroendocrine) - 25%

Adrenal cortex (True Endocrine) -75%

Question 2

What is the adrenal medulla?

Answer 2

Modified sympathetic ganglion derived from neural cresh tissue

Question 3

What does the adrenal medulla secrete?

Answer 3

Catecholamines, mainly epinephrine, also norepinephrine and dopamine

Question 4

What is an example of a glucocorticoid?

Answer 4

Cortisol (involved in maintaining plasma glucose)

Question 5

What is each layer of the adrenal cortex?

Answer 5

Zona glomerulosa (secretes aldosterone)

Zona fasciculate (secretes glucocorticoids)

Zona reticularis (secretes sex hormones)

Question 6

What enzyme is responsible for both the formations of aldosterone and cortisol?

Answer 6

21-hydroxylase

Question 7

Explain the process of a deficit in 21-hydroxylase causing adrenal hyperplasia?

Answer 7

1) Lack of enzyme inhibits synthesis of cortisol
2) Removal of negative feedback on ACTH and CRH release
3) Increased ACTH secretion is responsible for enlargement of adrenal glands
4) Negative feedback of ACTH on CRH synthesis remains balanced
5) Babies become very ill within a few days of birth

Question 8

What percentage of plasma cortisol is bound to carrier protein? (Cortisol Carrier Protein)

Answer 8

About 95%

Question 9

What happens when cortisol binds to its cytoplasmic glucocorticoid receptor?

Answer 9

Hormone receptor complex migrates to nucleas

Binding to DNA via a hormone-receptor element to alter gene expression, transcription and translation

Question 10

What kind of rhythm do cortisol plasma levels show, and what are they preceded by?

Answer 10

Circadian rhythm, preceded by a similar pattern of release of ACTH

Question 11

What time of day can the peak and lowest levels of plasma cortisol be obersed?

Answer 11

Peak - between 6am and 9am

Lowest - midnight

Question 12

Cortisol actions on glucose metabolism

Answer 12

• Gluconeogenesis
• Proteolysis
• Lipolysis
• Decrease insulin sensitivity- of muscles & adipose tissue (ensures glucose is available to to other vital cells?) - Cortisol opposes insulin

Question 13

Does cortisol have permissive action on insulin or glucagon?

Answer 13

Glucagon, which is vital as glucagon alone is inadequate in responding to a hypoglycaemia challenge

Question 14

State some non-glucocortiocoid actions of cortisol

Answer 14

• Reduces Ca2+ levels
• Impairmement of mood & cognition
• Immunosupression
• Permisive effects on noepinephrine - vasoconstriction= hypertension

Question 15

What does aldosterone act on?

Answer 15

Distal tubule of kidney to determine to determine levels of minerals reabsorbed/excreted

Question 16

How does aldosterone impact sodium and potassium?

Answer 16

Increases reabsorption of sodium and promotes excretion of potassium

Question 17

What is secretion of aldosterone by adrenal cortex primarily controlled by?

Answer 17

Renin-angiotensin-aldosterone system (RAAS)

Question 18

What system are the effects of aldosterone mainly on?

Answer 18

CVS system

Question 19

What does increased aldosterone cause?

Answer 19

Stimulates sodium (and water) retention and potassium depletion, resulting in increased blood volume and blood pressure

Question 20

What happens to preganglionic fibres to the adrenal medulla?

Answer 20

Terminate on specialised postganglionic cells in adrenal medulla, these postganglionic cells do not have axons, instead releasing their neurohormones (adrenaline) into the blood

Question 21

Why is care required when withdrawing chronic glucocorticoid treatment?

Answer 21

Due to enhanced negative feedback effects of exogenous control

Therapeutic cortisol also enhances negative feedback on hypothalamus and pituitary, reducing release of CRH and ACTH:

• loss of trophic action of ACTH on adrenal gland causes atrophy of gland
• risk of adrenal insufficiency if withdrawal is too fast