Endocrine System Flashcards
Where are mineralocorticoids produced?
Zona glomerulosa of the adrenal cortex
Where are glutocorticoids produced?
Zona fasciculata of the adrenal cortex
Give an example of a minerocorticoid
Aldosterone
What is the function of aldosterone?
Tubular reabsorption of Na+, Cl-
Tubular K+ excretion
Osmotic retention of H2O ; increase in blood pressure
Give an example of a glucocorticoid
Hydrocortisone
How is the synthesis and secretion of adrenal corticosteroids regulated?
Adrenocorticotrophic hormone (ACTH) stimulates synthesis and release of glucocorticoids (eg. hydrocortisone) from the adrenal cortex
Corticotrophin-releasing factor (CRF) from the hypothalamus regulates ACTH release and is regulated in turn by neural factors and negative feedback from plasma glucocorticoids.
Mineralocorticoid (aldosterone) release from the adrenal cortex is predominantly controlled by the renin angiotensin system
What is the mechanism of action of glucocorticoids?
Bind intracellular receptors which dimerise, migrate to the nucleus and interact with DNA to modify gene transcription and protein synthesis
Induce synthesis of some proteins and inhibit synthesis of others.
What is the mechanism of the anti-inflammatory/immunosupressive actions of glucocorticoids?
Inhibit the transcription of genes whose protein products are involved in the inflammatory response (COX-2)
Increase the expression of genes whose protein products are anti-inflammatory (annexin-1)
Describe the structure of the glucocorticoid receptor
The glucocorticoid receptor protein has 3 domains
Two zinc fingers are located in the central region and believed to wrap around the DNA helices.
There are also phosphorylation sites and regions of hormone-independent activation function (AF1) and hormone-dependent activation function (AF2) related to transcription.
What is the function of parathyroid hormones?
Controls blood calcium and phosphate levels
How does parathyroid hormone control blood calcium levels?
Stimulates release of Ca2+ from bone
Reabsorption of Ca2+ from urine
Absorption of Ca2+ from the gut
High plasma levels lead to decreased secretion via binding of Ca2+ to Ca2+ sensing GPCRs on parathyroid gland
Name two hormones secreted by the adrenal medulla
Adrenaline
Noradrenaline
What are the functions of adrenaline and noradrenaline?
- Control metabolism
- Cardiovascular function
- Response to stress
What are the effects of adrenaline?
- Increase in cardiac output
- Dilates bronchi
- Dilates pupils
- Relaxes gut smooth muscle
- Stimulates cortisol production/secretion
- Stimulates glucose release from liver
What types of hormones are released from the adrenal cortex?
Mineralocorticoids
Glucocorticoids
What are the functions of hydrocortisone?
Controls metabolism
Stress response
Suppression of immune response