Adrenal Glands Flashcards
Where are the adrenal glands?
one on top of each kidney
Each adrenal gland is structurally and functionally…
two endocrine glands in one:
- inner adrenal medulla
- outer adrenal cortex
What is the inner adrenal medulla made up of?
catecholamine-secreting nervous tissue, and acts as part of sympathetic nervous system
What does the outer adrenal cortex consist of?
steroid-secreting tissues
What forms the bulk (80%) of the adrenal gland?
outer adrenal cortex
What are the ‘cells’ of the adrenal medulla?
highly modified sympathetic postganglionic neuron
What do the cells of the adrenal medulla produce?
catecholamines
What are the two types of catecholamines?
- epinephrine (E) or adrenaline
- norepinephrine (NE) or noradrenaline
Where is epinephrine and norepinephrine stored?
in granules similar to neurotransmitter storage vesicles
When are large amounts of catecholamines released?
activation of sympathetic nervous system in response to stress (including exercise) or fight-or-flight response
When large amounts of catecholamines are released, how much is epinephrine, and how much is norepinephrine?
80% of it is E
20% of it is NE
How are cells of the adrenal cortex arranged?
into three zones:
- zona glomerulosa
- zona fasciculata
- zona reticularis
What does each zone of the adrenal cortex do?
produces several corticosteroids
What is zona glomerulosa, and what does it produce?
outer-most layer of cells that produces mineralocorticoids
What is zona fasciculata, and what does it produce?
middle zone composed of cells that secrete glucocorticoids (metabolic hormones)
What is zona reticularis, and what does it produce?
innermost (directly adjacent to adrenal medulla) layer that produces small amounts of adrenal sex steroid
Adrenal Cortex
What do mineralocorticoids do?
regulate Na+ and K+ balance and blood pressure homeostasis
Adrenal Cortex
What is aldosterone?
most potent mineralocorticoid in humans, and accounts for 95%+ of production
Adrenal Cortex
What is aldosterone release induced by?
elevated blood K+ and activation of renin-angiotensin system (RAS)
Adrenal Cortex
What is aldosterone’s primary target organs? What does it do there?
distal and collecting tubules of kidney, where it stimulates reabsorption of Na+ ions from urine back to bloodstream, while promoting elimination of K+
Mineralocorticoids – Diagram
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Adrenal Cortex
What do glucocorticoids do?
exert a wide range of actions in multiple target tissues
Adrenal Cortex
What is one type of mineralocorticoid?
aldosterone
Adrenal Cortex
What is one type of glucocorticoid?
cortisol
Adrenal Cortex
What is cortisol?
most important glucocorticoid in humans
Adrenal Cortex
What are cortisol’s target tissues?
liver, fat, muscle, intestines, CNS
Adrenal Cortex
What can cortisol regulate, and how?
plasma glucose levels by activating gluconeogenesis in liver
Adrenal Cortex
When does cortisol’s blood levels increase? What happens
increase significantly during stress – results in breakdown of adipose tissue and release of fatty acids, which can be used by many tissues as source of energy, “saving” glucose for the brain (“glucose sparing”)
Adrenal Cortex
What type of effects does chronic excess of cortisol have?
significant anti-inflammatory and anti-immune effects
Adrenal Cortex
What are glucocorticoid drugs used for?
to control symptoms of inflammatory disorders (ie. rheumatoid arthritis or allergic responses)
Adrenal Cortex
What are the metabolic effects of cortisol?
- increase hepatic gluconeogenesis
- increase lipolysis → increase fatty acids in blood (alternative fuel for most tissues)
- both effects – glucose sparing for brain (which is critical during prolonged stress)
Adrenal Cortex
What is cortisol secretion regulated by?
hypothalamic-pituitary-adrenocortical axis
Adrenal Cortex
Hypothalamic-Pituitary-Adrenocortical Axis – Diagram
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What is Addison’s disease?
uncommon disorder that occurs due to low cortisol, and often aldosterone, production
