The Adrenals and their hormones Flashcards
Where are the adrenal glands located
Above the kidneys
How many arteries and veins serve the adrenal glands
Many arteries by only one vein : inferior vena cava
Name the layers of the adrenal glands from outside in
Zona glomerulosa
Zona Fasciculata
Zona reticularis
Medulla
What does the medulla produce
Catecholamines e.g. adrenaline (80%) and noradrenaline
What does the zona glomerulosa produce
Mineralocorticoids e.g. aldosterone
What does the zona fasciculata produce
Glucocorticoids e.g. cortisol, androgens and oestrogen
What does the zona reticularis produce
Glucocorticoids, androgens and oestrogen
Describe the synthesis of steroid hormones form cholesterol
- liberation of the cholesterol from the ester by esterase
- stAR transports it to the inner mitochondrial membrane
- Pathway to form the mature hormone
- Hormone may freely diffuse through the membrane
Where does synthesis of steroid hormones occur
Gonads OR adrenals
What is the majority of steroid hormones bound to
Corticosteroid binding protein (CBG) and albumin
What does cortisol mainly bind to as it travels in the blood
CBG
What does aldosterone bind to as it travels in the blood
Albumin
When are cortisol levels highest and lowest
Highest in the morning, lowest in the afternoon
Which receptors does cortisol bind to
Glucocorticoid receptors and aldosterone receptors
Which receptors do aldosterone bind to
Aldosterone receptors
How do organs ensure aldosterone is taken up when needed
11b-HSB2 breaks it down into an inactive form so it cannot leave
Which tissues require aldosterone specifically
Kidney and placenta
What is the purpose of the renin-angiotensin system
Increase blood pressure
Where is renin produced
Granular cells of the kidney in the afferent arteriole
Which factors influence renin release
Renal perfusion pressure (Afferent arteriole pressure)
Renal sympathetic activity
Macular densa cells (low sodium recognised)
Describe the renin-angiotensin system
- Renin release is stimulated by low blood pressure or low sodium
- renin released and activates angiotensinogen from the liver
- angiotensin I formed and circulates
- Angiotensin converting enzyme (ACE) converts to angiotensin II
- angiotensin II activates the aldosterone producing cells in the zone glomerulosa of the adrenal glands
What is the feedback system for the hypothalami-pituitary-adrenocortical axis
ACTH stimulates the release of cortisol
Cortisol has a direct negative effect on the Adenohypophysis (-CRH) and an indirect negative effect on the hypothalamus
What are the principal physiological actions of adrenal hormones
Increase in sodium, bicarbonate and water resorption
What does aldosterone do
Movement of sodium from tubules in the kidney to the blood
