Exam 5: Adrenal Physiology Flashcards
What hormone comes from zona fasciculata?
Cortisol
What hormone comes from zona glomerulosa?
Aldosterone
What hormone comes from zona reticularis?
Androstenedione
What are examples of adrenocortical steroids/corticosteroids?
Glucocorticoids (cortisol) Mineralocorticoids (aldosterone) Sex steroids (progesterones, androgens, estrogens)
Which corticosteroid has the biggest physiologic effect?
Aldosterone
What is the adrenal gland composed of?
Adrenal cortex
Adrenal medulla
What comes from the adrenal cortex?
Steroid hormones
What occurs in the adrenal medulla?
Catecholamine synthesis
What is catecholamine released into?
Blood
What is catecholamine responsible for?
Fight or flight
What is the catecholamine in cats?
Norepinephrine
What is the catecholamine in digs and humans?
Epinephrine
What does catecholamine cause?
Increase in metabolic rate
Increase in BP, cardiac contractility, and myocardial excitability
What kind of regulation is the adrenal medulla under?
SNS
What are the layers of the adrenal cortex?
Glomerulosa
Fasciculata
Reticularis
What is the specific enzyme of the glomerulosa? What is the product?
Aldosterone synthase
Mineralocorticoids
What is the specific enzyme of the faciculata? What is the product?
17α-hydroxylase/P450c17
Glucocorticoids, sex hormones
What is the specific enzyme of the reticularis? What is the product?
17α-hydroxylase/P450c17
Glucocorticoids, sex hormones
What is the half-life of cortisol?
Less than 2 hours
What is the half-life of aldosterone?
About 20 minutes
Which steroids are active?
Those that are free/unbound
Where does cortisol have receptors?
In most cells
What are the cellular functions of cortisol?
Catabolic
Anti-inflammatory
Immunosuppressive
Anti-stress
What are the catabolic actions of cortisol?
Stimulate gluconeogenesis
Anti-insulin
Breaks down protein
Describe the catabolic effects of cortisol on carbohydrates
Stimulates hepatic gluconeogenesis*
Inhibits effects of insulin
Fight or flight
Protects from hypoglycemia
Describe the catabolic effects of cortisol on lipids
Mobilizes fatty acids
Redistribution
Describe the catabolic effects of cortisol on proteins
Inhibits cellular uptake of amino acids
Stimulates gluconeogenesis
Muscle breakdown*
Describe what happens with stress in a normal dog to synthesize cortisol
An increase in stress causes and increase in CRH from the hypothalamus. This leads to an increase of ACTH from the pituitary, which leads to an increase in cortisol from the adrenal gland
What happens to CRH when ACTH increases?
Decreases
What happens to CRH when cortisol increases?
Descreases
What happens to ACTH when cortisol increases?
Decreases
What is the release of aldosterone stimulated by?
Deceased blood volume
Decreased Na
Increased K
What is the primary function of aldosterone?
Increase Na, Cl, and water resorption
Increase K and H excretion
What is the site of action of aldosterone?
Principal cells of distal tubules and collecting ducts
What does aldosterone do to the principal cells of distal tubules and collecting ducts?
Increase activity of basolateral Na/K ATPse
Increase transcription of luminal Na channels
What regulates aldosterone?
Renin-angiotensin-aldosterone system (RAAS)
Describe renin
Released from afferent arteriole
Response to hypovolemia
Describe angiotensin
Renin converts angiotensinogen to angiotensin
AT converted to ATII by angiotensin converting enzyme in lungs
ATII stimulates aldosterone synthesis
What is the RAAS system directly stimualted by?
Increased K+
