Adrenal Glands Flashcards
What are the three parts of the adrenal gland?
- capsule
- cortex
- medulla
What are the different parts of the adrenal gland responsible for?
- cortex = steroidogenisis
- medulla = catecholamines
What are the three different parts of the adrenal cortex?
- zona glomerulosa (mineralocorticoids) - aldosterone
- zona fasiculata (glucocorticoids) - cortisol
- zona reticularis (androgen precursors)
What are corticosteroids?
mineralocorticoids and glucocorticoid hormones
What is the precursor for lipid derived hormones?
cholesterol
- hormones are synthesised on demand
- via conserved biosynthetic pathways
- enzymes found in mitochondria/ER
What is the rate listing step when synthesising lipid hormones?
cholesterol to prognenolone via prenenolone synthase
How is the enzyme pregnenolone synthase regulated?
by the Adrenocorticotropic Hormone (ACTH)
- CRH secreted by the hypothalamus
- causes ACTH secretion from the anterior pituitary
- ACTH induces the enzyme
therefore ACTH induces steriodogenesis
What is the main role of glucocorticoids?
- metabolic effects
- anti-inflammatory
- immunosuppressive
What is the main role of mineralocorticoids?
- water and electrolyte balance
How are corticosteroids transported in the blood?
TRANSCORTIN - Corticosteroid Binding Globulin
- binds 90% of cortisol
- binds 60% of aldosterone
will NOT bind to synthetic steroids - these bind to albumin
Why do steroids generally have longer-term actions?
because they induce changes in transcription and translation of genes, their effects are to induce synthesis of specific proteins - receptors are intracellular
aldosterone CAN have more immediate effects as some cells have receptors on the surface
How are glucocorticoids released?
hypothalamus detects stress/excitement/anticipation
- secretes CRH
- acts on the anterior pituitary to release ACTH
- ACTH acts on the adrenal glands, and induces PS
- cholesterol - prognenolone
- synthesis of cortisol begins
What effects does cortisol have on the body?
raises blood glucose:
- lipolysis
- protein catabolism
- glucogenesis
raises blood pressure:
- sensitises blood vessels to adrenaline
suppresses the immune system
- reduces inflammation
induces osteoclasts
What is involved in the negative feedback process?
cortisol acts back on the
- hypothalamus to stop the secretion of CRH
- anterior pituitary to stop the secretion of ACTH
What is the mechanism of action of mineralcorticoids?
binding of aldosterone to MC receptors causes:
- Na uptake
- Water reabsorption
- Increasing blood pressure
aldosterone release is triggered by
- angiotensin II
- low salt levels