The Adrenal Glands Flashcards
What types of hormones are produced by the adrenal cortex and give some examples
Mineralocorticoids - aldosterone
Glucocorticoids - cortisol and corticosterone
Androgens - dehydroepiandrosterone
What hormones are produced by the adrenal medulla and what cells produce them
Catecholamines: including adrenaline, noradrenaline and dopamine
Chromaffin cells
What are the three zones in the adrenal cortex and what hormones do they secrete
Zona glomerulosa - mineralocorticoids
Zona fasciculata - glucocorticoids
Zona reticularis - glucocorticoids and androgens
Describe how corticosteroids cause their effects
Diffuse across plasma membrane and bind to receptors
Binding causes dissociation of chaperone proteins with the receptor ligand complex translocating to the nucleus
Complex then either binds to glucocorticoid response elements (GREs) or to other transcription factors
What is the function of aldosterone
Causes Na and water reabsorption and K excretion in distal tubules and collecting duct of nephrons in the kidney
Acts on principal cells of distal tubule and collecting duct to upregulate expression of basolateral Na/K pump (3 Na into intersitial fluid and 2 K into cell)
Also upregulates expression of epithelial sodium channels in collecting duct and colon to promote Na absorption
Describe the control of cortisol secretion
ACTH from corticotropes of anterior pituitary control release of cortisol and is secreted under circadian rhythm
ACTH secretion is under control of CRF (corticotropin releasing factor) - secreted due to physical, emotional or chemical stressors
How is ACTH produced and what other peptides are produced along with ACTH
Produced by post-translational processing of POMC (pro-opiomelanocortin)
Peptides include: ACTH, α-MSH (melanocyte stimulating hormone), endorphins
What cells does ACTH stimulate and what does binding cause
Cells in zona fasciculata and reticularis
Causes activation of cholesterol esterase increasing concentration of free cholesterol
Stimulates other steps in synthesis of cortisol
What transport proteins transport cortisol in the plasma
Transcortin (corticosteroid-binding globulin (CBG))
Albumin (only ~10%)
What are the actions of cortisol
Decreased amino acid uptake
Decreased protein synthesis
Increased proteolysis in most tissues (not liver)
Increased hepatic gluconeogenesis and glycogenolysis
Increased lipolysis in adipose tissue
Decreased peripheral glucose uptake
Depress immune system
Anti-inflammatory effect by inhibiting macrophage activity and mast cell degradation
How are catecholamines produced by chromaffin cells
Series of enzyme catalysed reactions converting tyrosine (amino acid) to dopamine
Dopamine -> noradrenaline -> adrenaline
What are the actions of adrenaline and what receptors are stimulated
Increased cardiac output - increased heart rate (β1) and increased contractility (β1)
Increased blood supply to muscle - vasoconstriction to skin and gut (α1) and vasodilation to skeletal muscle (β2)
Increased mental alertness
Increased liver and muscle glycogenolysis
Increased glycolysis in muscle
Increased gluconeogenesis in liver
Increased lipolysis in adipose tissue
Bronchodilation (β2)
Increased renin secretion by kidney
Increased glucagon and decreased insulin secretion
Where are androgens secreted from and give an example of an androgen
From cells in zona reticularis
Dehydroepiandrosterone (DHEA)
What is DHEA converted to in males and females and what are is the function of androgens
Males - DHEA converted to testosterone in testes
Females - DHEA converted to oestrogens
Androgens promote axillary and pubic hair growth in both sexes
Female androgens also promote libido
