The Adrenals and their Hormones Flashcards

1
Q

What are the parts of the adrenal gland from the outside to the inside?

A

Zona Glomerulosa (aldosterone production) Zona Fasciculata (cortisol and sex steroids) Zona Reticularis (cortisol and sex steroids) Adrenal Medulla

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2
Q

What is the direction of blood flow in the adrenals?

A

From the cortex towards the medulla

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3
Q

What is produced by the adrenal medulla? What are the cells involved called?

A

Catecholamines by the Chromaffin cells

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4
Q

What is produced in the adrenal cortex? State the four hormones produced.

A

Corticosteroids: Mineralocorticoids - aldosterone Glucocorticoids - cortisol Sex Steroids - androgens and oestrogens

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5
Q

What is androstenedione?

A

It is a weak androgen that can be converted to testosterone and dihydrotestosterone

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6
Q

How are corticosteroids transported in the blood?

A

They bind to plasma proteins. There is so much albumin that some corticosteroids will non-specifically bind to albumin. There are more specific plasma proteins - corticosteroid binding globulin

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7
Q

Describe the difference in the blood concentrations of cortisol and aldosterone.

A

The concentration of cortisol is 1000 times greater than the concentration of aldosterone.

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8
Q

How does cortisol concentration vary?

A

Cortisol concentration changes with the circadian rhythm. It is a stress hormone so is released more at times of stress.

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9
Q

What are the effects of aldosterone?

A

Increased potassium and H+ secretion Increase sodium reabsorption

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10
Q

Describe the mechanism of action of aldosterone.

A

Aldosterone binds to intracellular receptors and translocates to the nucleus and causes changes in transcription leading to the synthesis of ion channels and pumps.

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11
Q

Describe the arrangement of the juxta-glomerular apparatus in the kidneys.

A

The juxta-glomerular cells are in contact with the afferent arteriole. The macula densa cells are next to the juxta-glomerular cells

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12
Q

What hormone is stimulated by an increase in plasma osmolality?

A

Vasopressin

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13
Q

What is a consequence of increase extracellular fluid volume?

A

Hypertension

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14
Q

Describe how the juxtaglomerular apparatus can lead to production of aldosterone.

A

Macula densa detects a decrease in tubular sodium concentration and stimulates the release of renin from the juxta-glomerular cells. Renin stimulates the production of angiotensin II, which upregulates aldosterone release.

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15
Q

State three causes of renin release.

A

Decreased renal perfusion pressure Increased renal sympathetic activity Decreased sodium concentration at the top of the loop of Henle

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16
Q

Describe the steps in the production of angiotensin II from the angiotensinogen.

A

Renin converts angiotensinogen (produced by the liver) to angiotensin I Angiotensin I is converted by ACE (which is found in high concentration in the lung endothelium) to Angiotensin II

17
Q

What are the effects of cortisol?

A

Increased hepatic gluconeogenesis Increase glycogenolysis Increased fat metabolism
Stimulates peripheral protein catabolism Enhances effects of glucagon and catecholamines

18
Q

What are the three effects of large amounts of cortisol?

A

Anti-inflammatory Immunosuppressive Anti-allergic

19
Q

Which receptors do a) aldosterone and b) cortisol bind to?

A

Aldosterone - mineralocorticoid receptors Cortisol - glucocorticoid receptors AND mineralocorticoid receptors

20
Q

As cortisol has a much higher blood concentration than aldosterone, why doesn’t cortisol constantly bind to mineralocorticoid receptors?

A

The kidneys have an enzyme called 11 beta-hydroxysteroid dehydrogenase 2 that converts cortisol into the inactive CORTISONE.

21
Q

Describe the mechanism of action of cortisol.

A

Cortisol binds to intracellular receptors, moves to the nucleus and causes a GENOMIC change.

22
Q

Describe the control of cortisol.

A

There is direct negative feedback by ACTH on the hypothalamus Cortisol also have negative feedback effects on the hypothalamus and on the adenohypophysis

23
Q

What is dehydroepiandrosterone (DHEA)?

A

This is a very weak androgen that peaks around 20-30 years. It is particularly important in post-menopausal women as a precursor for oestrogen.