Adrenal Gland Physiology Flashcards
where are the adrenal glands located
retroperitoneal space
cranial and medial to the kidneys
what are the layers of the adrenal gland
zona glomerulosa
zona fasciculata
zona reticularis
medulla
what does the zona glomerulosa produce
mineralocorticoids (aldosterone)
what does the zona fasciculata produce
glucocorticoids (cortisol)
what does the zona reticularis produce
androgens
what does the medulla produce
catecholamines (epi/NE)
what type of hormones are produced in the cortex
steroids (derivatives of cholesterol)
what is the function of aldosterone
maintain sodium and potassium balance and ECF volume
what is the main target of aldosterone
kidneys
promotes sodium reabsorption and potassium excretion
what are the main regulators of aldosterone secretion
- RAAS system
- Na/K concentration
- ACTH
what is the main stimuli for the RAAS system
low renal blood flow
low Na/Cl delivery
SNS innervation
RAAS overview
- JGA senses stimuli and secrete renin
- renin converts angiotensinogen –> ANG I
- ACE (lungs) converts ANG I –> ANG II
- ANG II stimulates aldosterone secretion, vasoconstriction, and NE/epi/ADH secretion
hyperaldosteronism
Conn’s syndrome; RARE
caused by a primary aldosterone secreting tumor in the adrenal cortex (glomerulosa)
what electrolyte imbalances are caused by hyperaldosteronism
hypokalemia
hypernatremia
what is the main clinical sign of hyperaldosteronism
hypertension
hypoadrenocorticism
Addison’s disease
caused by immune mediated destruction of all adrenal cortical layers
what electrolyte imbalances are caused by hypoadrenocorticism
hyponatremia
hyperkalemia
can get hypoglycemia
what are the main clinical signs of hypoadrenocorticism
hypovolemia
cardiac arrhythmias
what test can be used to diagnose hypoadrenocorticism
ACTH stimulation test
cortisol levels will NOT increase following exogenous ACTH administration
function of cortisol
many functions (metabolic, immune, cardiovascular, renal)
what are the targets of cortisol in the body
all tissues express cortisol receptors
what receptor type does cortisol use
cytosolic
pituitary dependent hyperadrenocorticism (PDH)
Cushing’s disease caused by a primary pituitary tumor that secretes excess ACTH
leads to overstimulation of the adrenal cortex (zona fasciculata) with loss of negative feedback on ACTH
what lesion is associated with pituitary dependent hyperadrenocorticism
bilateral adrenal gland enlargement
adrenal dependent hyperadrenocorticism
Cushing’s caused by a primary adrenal tumor that secretes excess cortisol
what lesion is associated with adrenal dependent hyperadrenocorticism
unilateral adrenal mass
contralateral adrenal atrophy
what is the difference in serum ACTH levels in pituitary dependent and adrenal dependent hyperadrenocorticism
pituitary dependent: HIGH ACTH from lack of negative feedback
adrenal dependent: LOW ACTH from negative feedback
what cell type is found in the adrenal medulla
chromaffin cells
chromaffin cells
synthesize and secrete catecholamines
extension of SNS - acts as a postganglionic sympathetic neuron w/o axons
what controls catecholamine secretion from chromaffin cells
sympathetic innervation
what is the primary stimuli for catecholamine release
stress
hemorrhage, hypoxia, hypotension, hypoglycemia, low perfusion, anesthesia, surgery, fear
function of catecholamines
regulate cardiovascular and metabolic processes
what are the targets of catecholamines
many - the action depends on the receptor type
what are the cardiovascular receptors and effects of catecholamines
a1: vasoconstriction
a2: inhibits NE reuptake, decreases BP
B1: increase HR/contractility, stimulates renin
B2: vasodilation and bronchodilation
what are the metabolic receptors and effects of catecholamines
a and B receptors - main goal is to increase blood glucose
liver: stimulate gluconeogenesis and glycogenolysis
adipose: stimulate lipolysis
pancreas: inhibits insulin secretion and stimulates glucagon secretion
pheochromocytoma
adrenal medulla tumor that episodically secretes excess catecholamines
what are the clinical signs of a pheochromocytoma
episodic: weakness, collapse, panting, tachypnea, tachycardia, arrhythmias, systemic hypertension, hyperglycemia
