Pituitary adrenal axis Flashcards
What do the hormones of the adrenal gland important for?
Regulators of metabolism and play an important role in adaptation to stress.
What is cortisol
A glucocorticoid that increases plasma glucose levels.
What can a deficiency in cortisol lead to?
Hypoglycaemia
What is aldosterone?
A mineralocorticoid that promotes salt and water retention by the kidney. It is critical form normal salt/water balance.
What is the primary produce of chromaffin cells in the medulla.
Epinephrin
What does stress stimulate in the short term stress response?
The hypothalamus will activate the adrenal medulla via nerve impulses.
What does the adrenal cortex secrete in short-term stress response.
Epinephrine and norepinephrine.
What does stress stimulate in the long term stress response.
The hypothalamus will activate the adrenal cortex through hormonal stimulus.
What does the adrenal cortex secrete during the long term stress response.
mineralocorticoids and glucocorticoids
Where are the enzymes that produce steroid hormones from cholesterol located?
The mitochondria and SmER
how is the rate limiting step in steroid hormone synthesis carried out?
The transport of free cholesterol from the cytoplasm into the mitochondria. It’s carried out by the Steroidogenic Acute Regulatory Protein (StAR). This moves cholesterol from the outer membrane to the inner membrane where it is converted to pregnenolone. This step is non-reversible.
What determines which pathway pregnenolone takes?
Regulated by specific enzymes
Different zones of the adrenal cortex have different relative activities of enzymes, resulting in different chemical reactions taking place.
Where is the largest and most active steroidogenic zone?
The middle zona fasciculata producing the glucocorticoid hormone, cortisol.
How is cortisol transported in the blood?
Predominantly bound to corticosteroid-binding globulin (CGB)-about 90% and also albumin- about 5%-7%. The free form of the hormone -3-5% exerts biological effects within target cells and feeds back onto the piuitary and hypothalamus.
What are some metabolic effects of cortisol?
-Stimulates protein and triglyceride catabolism.
-Stimulates “gluconeogenesis” in liver
-inhibiton of glucose uptake by body elevates blood blood glucose levels
-inhibits bone formation
-Inhibition of non-essential functions
