L16: Adrenal Glands

Question 1

Where are the adrenal glands?

Answer 1

Superior to each kidney; lie against diaphragm in retroperitoneal space

Question 2

State the 3 layers of the adrenal gland, outer to inner

Answer 2

• Capsule: connective tissue containing plexus of blood vessels
• Cortex: Zona glomerulosa, zona fasiculata, zona retiuclaris
• Medulla

Question 3

State the 3 layers of the adrenal cortex and what hormones each secretes

Answer 3

Question 4

In embryonic development, state where each is derived from:

• Cortex
• Medulla

Answer 4

• Cortex: mesoderm
• Medulla: neural crest cells

Question 5

What the general role of mineralocorticoids

Answer 5

Regulate Na⁺ and K⁺ levels

Question 6

What is the general role of androgens?

Answer 6

Sex hormones

Question 7

How many carbon atoms in:

• Mineralocorticoids
• Glucocorticoids
• Androgens

Answer 7

• Minearlcorticoids & glucocorticoids= 221
• Androgens= 19

Question 8

What is the general role of glucocorticoids?

Answer 8

Regulate carbohydrate metabolism (and others)

Question 9

What are steroid hormones synthesised from and where in the body are they synthesised?

Lipid or water soluble?

Answer 9

Synthesised from cholesterol in the adrenal cortex and gonads

Lipid soluble

Question 10

State some examples of steroid hormones

Answer 10

• Glucocorticoids
• Mineralocorticoids
• Androgens
• Oestrogens
• Progestins

Question 12

Describe how corticosteroids, an example of a lipid soluble steroid hormone, regulates gene transcription

Answer 12

1. Diffuse across plasma membrane
2. Bind to glucocorticoid receptor in cytoplasm
3. Binding causes dissociation of chaperone proteins
4. Receptor-ligand complex translocates to nuclues
5. Receptors bind to glucocorticoid response elements (GREs) and undergo receptor dimerisation or bind to other transcription factors

Question 13

What is the most abundant corticosteroid?

Answer 13

Cortisol.

It is a glucocorticoid and accounts for 95% of glucocorticoid activity

Question 14

Which hormones control cortisol production in the zona fasiculata in adrenal cortex?

Answer 14

• CRH (corticotropin releasing hormone) from hypothalamus
• ACTH (adrenocorticotropic hormone) from anterior pituitary

Question 15

Given that cortisol is lipid solube, how is it transported in blood?

Answer 15

• 90% bound to transcortin (corticosteroid-binding globulin)
• 10% bound to albumin

Question 16

State some of the effects of glucocorticoid hormones

Answer 16

• Anti-inflammatory effects (inhibits mast cell and macrophage degranulation)
• Depression of immune system

Question 17

CRH causes anterior pituitary to release ACTH which causes adrenal cortex to produce cortisol; but what causes CRH rease

Answer 17

• Temperature
• Pain
• Hypoglycaemia
• Emotional stressors
• Negative feedback

Question 18

Cortisol has a circadian rhythm; state when it is highest and lowest

Answer 18

Peaks in morning troughs around midnight

Question 19

ACTH is released in a circadian rhythm; state when it is high and when it is low

Answer 19

• High: early hours or morning
• Low: late evening

Question 20

Whats the half life of ACTH?

Answer 20

8 minutes

Question 21

Describe how ACTH acting at adrenal cortex causes cortisol production and release

Answer 21

1. ACTH interact with GPCRs (melanocrotin receptor) on cell surface of cells in zona fasciculata (and reticularis)
2. Binding activates cholesterol esterase
3. Increases conversion of cholesterol esters to free cholesterol
4. Cortisol produced from cholesterol

Question 22

Describe the structure and function of the adrenal medulla

Answer 22

• Is a modified sympathetic ganglion of ANS; contains chromaffin cells whihc are modified neurones that release hormones, that they have synthesised, when nerve inpulse arives
• Synthesises and released catecholamines e.g. adrenaline, noradrenaline, dopamiine

Question 23

Roughly how much of following hormones do chromaffin cells in adrenal medulla produce?

• Adrenaline
• Noradrenaline

Answer 23

• Adrenaline: 80%
• Noradrenaline: 20%

Question 24

Describe the steps that occur in chromaffin cells to produce catecholamines

Answer 24

Series of enzyme catalysed steps:

1. Tyrosine to dopamine
2. Dopamin to noradrenaline
3. Most of noradrenaline converted to adrenaline by N-Methyl transferase BUT 20% of chromaffin cells lack the enzyme so it is released as noradrenaline

Question 25

Describe the hormonal actions of adrenaline on: * CVS * Respiratory * CNS * Carbohydrate metabolism * Lipid metabolism

Answer 25

* CVS: increase CO * Respiratory: bronchodilation * CNS: increase alertness * Carbohydrate metabolism: increase glycogenolysis in liver and muscle * Lipid metabolism: increase lipolysis in adipose

Question 26

Describe the 2 main types of adrenergic receptors

Answer 26

* **Alpha:** subtypes 1 (facilitates increase in intracellular Ca²⁺) and 2 (facilitates increase in intracellular cAMP) * **Beta:** 1,2 & 3 increase cAMP

Question 27

Describe which pathway each of following activates: * B1 * B2 * A1 * A2

Answer 27

Question 28

Describe how adrenaline increases heart rate?

Answer 28

Question 29

What is the most abudant mineralocorticoid?

Answer 29

Aldosterone

Question 30

Aldosterone is a steroid hormone hence it is lipid soluble; how is it transported in blood?

Answer 30

Bound to **albumin USUALLY** or **sometimes transcortin**

Question 31

Why does aldosterone have a central role in regulation of plasma sodium, potassium and hence arterial blood pressure?

Answer 31

Aldosterone increases expression of Na⁺/K⁺ pump in nephron hence increases Na⁺ and hence water reabsorption *\*Also upregulates expression of ENaCs (epithelial sodium channels) in collecting ducts and colon to further increase Na⁺ reabsorption*

Question 32

Describe the RAAS, focus on aldosterones role in RAAS

Answer 32

Question 33

What is the role of the zona reticularis? What happens to the hormones it secretes?

Answer 33

Secretes weak androgens (DHEA & androstenedione) * Males: DHEA converted into testosterone in testes *(after puberty this is insignificant as testets secerete more testosterone)* * Females: adrenal androgens converted to oestrogens y other tissues *(after menopause this is the only source of oestrogens)*

Question 34

What do androgens, synthesised and released in the zona reticularis, promote in both sexes?

Answer 34

Axillary and pubic hair

Question 35

What 3 regions do all steroid hormones have?

Answer 35

* DNA binding region * Hydrophobic hormone binding region * Variable region

Question 36

There is sequence homology in hormone binding regions of steroid hormones; what are the consequences of this?

Answer 36

Cortisol (a glucocorticoid) will bind to mineralocorticoid and androgen receptors with low affinity- only becomes significant when cortisol levels high

Question 37

Compare corticosteroids and catecholamines, include: * What they are derived from * What receptors they bind to * Speed of response

Answer 37