S9 L1 - The Adrenal Gland

Question 1

• *Adrenal gland**
• What is the structure of this gland?
• Hormones secreted from each part?

Answer 1

• Capsule
• Cortex:
  zona glomerulosa salt*
  zona fasiculata sugar *
  zona reticularis sex*
• Medulla Adrenaline

*All corticosteroids

Question 2

• *Steroid hormones:**
• Synthesised from____
• ____ soluble
• Type of receptor____. These receptors work to____

How do corticosteriods exert their actions… (think about the receptor, explain the process…)

Answer 2

• Synthesised from cholesterol
• Lipid soluble hormones
• Type of receptor: nuclear receptor. These receptors work to modulate gene transcription

How do corticosteriods exert their actions… (think about the receptor, explain the process…) pic
• Corticosteroids readily diffuse across plasma membrane
• Bind to glucocorticoid receptors.
• Binding causes dissociation of chaperone proteins (e.g. heat shock protein 90)
• Receptor ligand complex translocates to nucleus
• Dimerisation with other receptors can occur
• Receptors bind to glucocorticoid response elements (GREs), or other transcription factors

Question 3

• *Aldosterone**
• Is it lipid or water soluble?
• How does aldosterone travel in the blood?
• Type of receptor?
• What is the role of aldosterone?
• How does aldoesterone fit into the RAAS?

Answer 3

• Lipid or water soluble?
  Lipophilic (lipid soluble)
  - How does aldosterone travel in the blood?
  Carrier protein - serum albumin and transcortin
  - Type of receptor?
  Intracellular receptor and exerts its actions by regualting gene transcription
  - What is the role of aldosterone?
  • Aldoesterone plays central role in regulation of plasma Na+ , K+ and arterial blood pressure.
  • Main actions in distal tubules and collecting ducts of nephron where it promotes expression of Na+/K+ pump promoting reabsorption of Na+ and excretion of K+ thereby influencing water retention, blood volume & therefore blood pressure.
  - How does aldoesterone fit into the RAAS?
  pic

Question 4

• *Cortisol
• ** Negative feedback to hypothalamus inhibits ____ and ____
• Transport protein _________
• How does cortisol exert its action ________
• Role (what does it do?)
• HPA for cortisol

Answer 4

- Negative feedback to hypothalamus inhibits ACTH and cortisol
- Transport protein: Transcortin
- How does cortisol exert its action: Nuclear receptor, exerts its action by regulating gene transcription
- Role (what does it do?)
• Net effects:
- Increased glucose production
- Breakdown of protein
- Redistribution
- Inhibits insulin-induced GLUT4 translocation in muscle (prevents glucose uptake)
• Increased protein breakdown in muscle
• Increased lipolysis in fat
• Increased gluconeogenesis in liver
• Resistance to stress (increased supply of glucose, raise blood pressure by making vessels more sensitive to vasoconstrictors)
• Anti-inflammatory effects (inhibits macrophage activity + Mast cell degranulation)
• Depression of immune response (prescribed to organ transplant patients)
- HPA for cortisol
pic

Question 5

• *Steroid Drugs -**
• Most commonly prescribed ones
• Conditions it is used to treat
• Important point with steroid use…

Answer 5

Steroid Drugs -
- Most commonly prescribed ones:
Prednisolone, Dexamethasone
- Conditions it is used to treat:
Asthma, Inflammatory bowel disease, Rheumatoid arthritis,
- Important point with steroid use…
Steroid dosage should be reduced gradually and not stopped suddenly!

Question 6

• *Androgen**
• Does the zona reticularis secrete many androgens?
• Males - how much significance does this androgen secretion have?
• Females - how much significance does this androgen secretion have?

Answer 6

- Does the zona reticularis secrete many androgens?
Secretes weak androgens
- Males - how much significance does this androgen secretion have?
In men, testosterone secreted in testes is significantly greater than the abmount secreted from zona reticularis
- Females - how much significance does this androgen secretion have?
In females adrenal androgens promote libido and are converted to oestrogens by other tissues. After menopause this is only source of oestrogens

They promote axillary and pubic hair growth in both sexes

Question 7

• *Adrenal medulla - Adrenaline**
• How does this fit into the sympathetic nervous system?
• How is adrenaline made?

Answer 7

- How does this fit into the sympathetic nervous system?
Adrenal medulla is a modified sympathetic ganglion of autonomic nervous system.
Chromaffin cells in adrenal medulla lack axons but act as postganglionic nerve fibres that release hormones into blood: Adrenaline (~80%) Noradrenaline (~20%)
- How is adrenaline made?
Tyrosine —-> Dopamine -> Noradrenaline -> Adrenaline

Question 8

• *Adrenergic receptors**
• 4, think back to ICPP

Answer 8

Question 9

• *Hormonal actions of adrenaline**
• What types of receptors in heart, lungs and blood vessels

Answer 9

1 heart, 2 lungs

Fight and flight