Adrenals and their Hormones 8 Flashcards

1
Q

Describe the rough anatomy of the Adrenals

A

They are located at the superior pole of the kidneys. They each have their own capsules and have many arteries supplying them but only one vein each. The right adrenal vein drains into the IVC and the left adrenal vein drains into the renal vein.

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2
Q

Describe Specific anatomy of the Adrenals

A

Comprised of a medulla and a cortex. The cortex produces corticosteroids while the medulla produces catecholamines

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3
Q

What are the sections of the cortex (from medulla out)?

A

Zona Reticularis
Zona Fasciculata
Zona Glomerulosa

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4
Q

How does blood get to the various zones?

A
  • Flows through the cells in each zones from the exterior of the gland
  • There are some vessels which flow through the cortex to get to the medulla
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5
Q

What is the medulla made of?

A

CHROMAFFIN CELLS and therefore associated to the produced catecholamines

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6
Q

What type of hormone does the cortex produce?

A

Steroids (therefore they are corticosteroids)

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7
Q

What does the medulla produce?

A

Catecholamines:

  • Adrenaline (80%)
  • Noradrenaline (20%)
  • Dopamine (V.small amounts)
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8
Q

What does the cortex produce?

A

Cortiocsteroids:

  • Mineralocorticoids = aldosterone
  • Glucocorticoids = Cortisol
  • Sex Steroids = androgens/oestrogens
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9
Q

Where is aldosterone produced?

A

Zona Glomerulosa

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10
Q

What are Cortisol and androgens/oestrogens produced?

A

Zona Fasciculata and Reticularis

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11
Q

What are adrenal cortical hormones synthesised from?

A

Cholesterol

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12
Q

Describe Cortisol Synthesis

A

1) Cholesterol
2) Pregnenolone
3) 17alpha-pregnenolone
4) 17alpha-progesterone
5) 11-deoxycortisol
6) Cortisol

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13
Q

Describe Aldosterone Synthesis

A

1) Cholesterol
2) Pregnenolone
3) Progesterone
4) 11-deoxycorticosterone
5) Corticosterone
6) Aldosterone

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14
Q

Describe Sex hormone Sythesis

A

1) Cholesterol
2) Pregnenolone
3) 17alpha-pregnenolone
4) Dehydroepiandrosterone
5) Androstenedione
6) Testosterone

Then either:

  • Oestrodiol
  • Dihydrotestosterone
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15
Q

What is the precursor to oestrogens?

A

Androgens

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16
Q

Describe Cortisol Transport

A
  • Corticosteroid Binding Globulin (CBG) (80%)
  • Albumin (10%)
  • Bioactive (10%)
17
Q

Describe Aldosterone Transport

A
  • CBG (15%)
  • Albumin (45%)
  • Bioactive (40%)
18
Q

When is cortisol released?

A

It is released at different times of the day (more in the morning). It is also released in pulses (pulsatile rhythm) on top of circadian rhythm

19
Q

What receptor does aldosterone act on?

A

Mineralocorticoid receptor

20
Q

What does Cortisol act on?

A

Mineralocorticoid and Glucocorticoid Receptors

21
Q

How do tissues prevent Cortisol acting on Mineralocorticoid Receptors?

A

Some tissues have enzymes (kidney) that converts bioactive Cortisol to Cortisone (inactive). This enzyme is 11b-hydroxysteroid dehydrodgenase 2 (11bhsb2). This enzyme is present in the kidneys and the placenta

22
Q

What is the action of Aldosterone?

A
  • STIMULATE NA+ RE-ABSORPTION in the distal convuluted tubule and cortical collecting duct.
  • STIMULATES K+ AND H+ SECRETION in the distal convuluted tubule and the collecting duct. This is for pH regulation of blood.
23
Q

What is Aldosterone the end product of ?

A

Renin-Angiotensin System

24
Q

Where is Renin released?

A

In the nephron, Macula Densa cells on the distal convuluted tubule sense Na+ concentration. These are in close proximity to the granular cells that line the afferent arteriole. These cells communicate and cause the granular cells to release the renin.

25
Q

What causes Renin to be released from the granular cells?

A
  • a decrease in perfusion pressure (detected by the granular cells)
  • Renal sympathetic activity (the juxta-glomerular apparatus is innervated)
  • Low Na+ detected by the Macula Densa which communicate to the Granular cells
26
Q

Process of the Renin-Angiotensin-Aldosterone system

A

1) Liver produces angiotensinogen
2) Renin (from the juxta-glomerulus apparatus) cleaves this to Angiotensin 1
3) ACE (high conc in lungs) cleaves this to Angiotensin 2
4) Angiotensin 2 stimulates the zona glomerulosa to produce aldosterone
5) Angiotensin 2 also stimulates vasoconstriction and regulates ions.
6) Corticotrophin enhances the system (has a permissive effect)

27
Q

Which two proteins does Aldosterone upregulate on the distal convuluted tubule and the collecting duct?

A
  • Na+ channels in the tubule lumen membrane

- Na-k+ ase which is inserted into the interstitial membrane

28
Q

What are the metabolic effects of Cortisol?

A

Overall increase in blood glucose:

  • increased hepatic gluconeogenesis
  • stimulates glycogen turnover
  • fat metabolism
  • enhances glucagon and catecholamines
  • some mineralocorticoid effects
  • some renal and cardiovascular effects
29
Q

What are the physiological effects of Cortisol?

A
  • reduces blood flow to skeletal muscle and fat tissue

- reduces entry of glucose into these tissues

30
Q

Whats another effect of Cortisol?

A
  • enhances memory within the hippocampus

- it works with serotonin to proliferate granular cells in the hippocampus (more branches = better memory)

31
Q

Pharmacological effect of Large amounts of Cortisol?

A
  • Anti-inflammatory
  • Anti-allergic
  • Immunosuppresive
    Increased by caffeine and alcohol levels
32
Q

Describe Cortisol control

A

The cortiocotrophs are controlled by hypothalamic neurones. Cortisol has a negative feedback affect on the pituitary and indirectly on the hypothalamus.

ACTH has an auto-negative feedback to the hypothalamus.

The circadian clock also control release