L53 - Adrenal gland Flashcards
What parts of the adrenal gland secrete hormones? which ones? (2)
- adrenal medulla - catecholamines
- adrenal cortex - minerlocorticoids, glucocorticoids
What do catecholamines do?
- regulation of secretion
- (+ actions)
What do mineralocorticoids do? (2)
- actions of aldosterone
- regulation by renin-angiotensin system
What do glucocorticoids do? (3)
- regulation of cortisol secretion
- role of H-P-A
- (+ actions)
What is the hormone cascade to reach adrenaline in the adrenal medulla? (5)
- tyrosine
- DOPA
- dopamine
- noradrenaline
- adrenaline
What is the regulation of secretion like?
- adrenal medulla part of sympathetic div of ANS
- specialiseed group of postganglionic neurons
- controlled by sympathetic pregranglionic nerve fibres
What are the effect of medullary catecholamines?
- direct activation of sympathetic nerves - lasts longer, generalised effect to all cells with a/B- receptors (GPCRs)
- major physiological effect on cardiac output and cellular metabolism
What are the actions adrenal catecholamines like? (2)
- through sympathetic div of ANS
- plasma adrenaline exceeds threshold for metabolic and cardiovascular effect
What are the different zones in the adrenal cortex? (3), what are they differentiated by?
- zona glomerulosa
- zona fasciculata
- zona reticularis
- dif expression of enzymes
What does aldosterone do (actions)? (3)
- stim reabsorption of Na+/excretion of K+ in cortical collecting ducts (by using Na-K-ATPase)
- dec ratio of [Na+] to [K+] in sweat and saliva
- inc reabsorption of Na+ in colon, excretion of K+ in faeces
What does the tetra planar ring tell us? (2)
- it’s a steroid
- it’s lipophilic
What is the overall + net effect of aldosterone?
- overall - retain Na+, expense K+
- net effect - inc plasma vol, = cardioV P
How is the renin-angiotensin system involved in the release of aldosterone? (5)
- BP drops, sensed by stretch receptors at the entry of the tubular nephron
- releases renin
- angiotensin I converted to angiotensin II
- constrict blood vessels = inc BP
- aldosterone released - inc Na+ retention = inc BP
What are the main glucocorticoids synthesised? (2)
- rodents - corticosterone
- humans - cortisol
What is the regulation of glucocorticoid secretion? (5)
- regulated by hypothalamus and pituitary
- CRH released
- acts on pituitary
- causes ACTH to be released = release of cortisol from adrenals
- +ve fb to tissue actions, -ve feedback to hypothalamus and pituitary
What is the HPA axis?
- CRH-ACTH-cortisol sequence
- stress inc CRH secretion (from H)
- inc plasma CRH in hypothalamo-pituitary portal vessels
- inc ACTH secretion (from anterior P)
- inc plasma ACTH
- inc cortisol secretion (from A)
- ins plasma cortisol
- -ve fb and target cells for cortisol
What is the circadian rhythm in cortisol secretion?
- fluctuations in cortisol caused by fluctuations in ACTH sec from P
- important in using GC treatments
- on/off switch driven by H RH
What are the metabolic actions of GCs? (5)
- affect muscle, liver, fat
- inc proteolysis and lipolysis - products used for gluconeogensis
- inc enzyme synthesis
- = inc gluconeogensis
- = inc plasma [glucose] (indirect)
What does cortisol do in the liver? (5)
- binds and translocates to nucleus
- regulates gene transcription
- inc AA transporters - inc uptake of AA for gluconeogenesis
- inc enzyme synthesis - inc glyconeogenesis = inc glycogen formation and storage
- = inc plasa glucose
What is addison’s disease? (3)
- cortisol deficiency
- autoimmune destruction
- red cortisol = wide range of effects to homeostasis
What is cushing’s disease? (3)
- corticol excess
- treatment related
- xs cortisol = wide range of effects to homeostasis
What does excess corticosteroids lead to? (5)
- inc plasma glucose levels
- causes inc in proteolysis = muscle wasting, skin thinning
- causes in fat redistribution/metabolism = moon face, buffalo hump
- causes inc breakdown of triglycerides = inc plasma FA levels
- supress inflammation and immune response
