The Adrenals and their Hormones Flashcards
What are the parts of the adrenal gland from the outside to the inside?
Zona Glomerulosa (aldosterone production) Zona Fasciculata (cortisol and sex steroids) Zona Reticularis (cortisol and sex steroids) Adrenal Medulla
What is the direction of blood flow in the adrenals?
From the cortex towards the medulla
What is produced by the adrenal medulla? What are the cells involved called?
Catecholamines by the Chromaffin cells
What is produced in the adrenal cortex? State the four hormones produced.
Corticosteroids: Mineralocorticoids - aldosterone Glucocorticoids - cortisol Sex Steroids - androgens and oestrogens
What is androstenedione?
It is a weak androgen that can be converted to testosterone and dihydrotestosterone
How are corticosteroids transported in the blood?
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
Describe the difference in the blood concentrations of cortisol and aldosterone.
The concentration of cortisol is 1000 times greater than the concentration of aldosterone.
How does cortisol concentration vary?
Cortisol concentration changes with the circadian rhythm. It is a stress hormone so is released more at times of stress.
What are the effects of aldosterone?
Increased potassium and H+ secretion Increase sodium reabsorption
Describe the mechanism of action of aldosterone.
Aldosterone binds to intracellular receptors and translocates to the nucleus and causes changes in transcription leading to the synthesis of ion channels and pumps.
Describe the arrangement of the juxta-glomerular apparatus in the kidneys.
The juxta-glomerular cells are in contact with the afferent arteriole. The macula densa cells are next to the juxta-glomerular cells
What hormone is stimulated by an increase in plasma osmolality?
Vasopressin
What is a consequence of increase extracellular fluid volume?
Hypertension
Describe how the juxtaglomerular apparatus can lead to production of aldosterone.
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.
State three causes of renin release.
Decreased renal perfusion pressure Increased renal sympathetic activity Decreased sodium concentration at the top of the loop of Henle