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bioregulatory systems 🦠 > adrenal gland > Flashcards

adrenal gland Flashcards

1
Q

where are the adrenal glands located

A

above the kidneys

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2
Q

where does the left adrenal vein drain into

A

the renal vein

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3
Q

where does the right adrenal vein drain into

A

the inferior vena cava (IVC)

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4
Q

how many veins and arteries do the adrenals have

A

many arteries but only 1 vein

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5
Q

microanatomy of the adrenal glands

A

adrenal cortex which has 3 layers - zona glomerulosa/fasciculata/reticularis
adrenal medulla

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6
Q

what does the adrenal cortex secrete

A

corticosteroids

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7
Q

what does the adrenal medulla secrete

A

catecholamines

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8
Q

what does the adrenal medulla do

A

secretes catecholamines by neuroendocrine/chromaffin cells
adrenaline/epinephrine 80%
noradrenaline/norepinephrine 20%
dopamine

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9
Q

what does the adrenal cortex do

A

secretes corticosteroids
mineralocorticoids (aldosterone)
glucocorticoids (cortisol)
sex steroids (androgens, oestrogens)

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10
Q

what zona secretes aldosterone

A

zona glomerulosa

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11
Q

what zona secretes cortisol (androgens and oestrogens)

A

zona fasciculata and reticularis

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12
Q

where do steroid hormones come from

A

cholesterol

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13
Q

what is the precursor for adrenal gland secretions

A

cholesterol

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14
Q

how many carbons does cholesterol have

A

27

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15
Q

what is an enzyme

A

a protein that catalyses a specific reaction
various enzymes are present in cells
specific enzymes catalyse the synthesis of particular alterations to the molecule

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16
Q

what is the pathway to get from cholesterol to aldosterone

A

cholesterol undergoes side chain cleavage > pregnenolone
pregnenolone is oxidised by 3 beta hydroxysteroid dehydrogenase > progesterone
progesterone is oxidised 3 times by 21, 11, 18 hydroxylases > aldosterone

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17
Q

what is the pathway to get from cholesterol to cortisol

A

cholesterol undergoes side chain cleavage > pregnenolone
pregnenolone is oxidation by 3 beta hydroxysteroid dehydrogenase > progesterone
progesterone is oxidised by 17, 21, 11 hydroxylases to form cortisol

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18
Q

what does aldosterone do

A

controls blood pressure
conserves Na by stimulating its reabsorption
stimulates K+ and H+ secretion

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19
Q

where does aldosterone stimulate Na reabsorption and K+/H+ secretion

A

in distal convoluted tubule and cortical collecting duct in the kidney
and in sweat glands, gastric glands and colon - Na reabsorption

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20
Q

how is aldosterone regulated (4)

A
  • by renin release when blood pressure falls (stimulates other cells)
  • increased renal sympathetic activity (directed to JGA cells) juxtaglomerular apparatus
  • decreased Na+ load to the top of loop of Henle (macula densa cells)
  • noradrenaline
21
Q

what is associated with decreased arterial blood pressure

A

decreased renal perfusion pressure

22
Q

what does renin do

A

stimulates conversion of angiotensinogen to angiotensin 1

23
Q

what converts angiotensin 1 to 2

A

ACE

24
Q

what does angiotensin 2 do

A 
regulator of aldosterone release
binds to receptors in zona glomerulosa
causes vasoconstriction (increased BP)
25
Q

what does aldosterone do

A

increases blood volume > increases BP

26
Q

what are the effects of angiotensin 2 on the adrenals

A 
activation of the following enzymes
side chain cleavage
3 hydoxysteroid dehydrogenase
21 hydroxylase
11 hydroxylase
18 hydroxylase
27
Q

summary of action of aldosterone

A

cholesterol > aldosterone > controls BP, increases sodium and lowers potassium

28
Q

when is cortisol released

A

normal stress response

29
Q

what are metabolic effects of cortisol

A

peripheral protein catabolism (break down for energy)
hepatic gluconeogenesis
increased blood glucose concentration
fat metabolism (lipolysis in adipose tissue)
enhanced effects of glucagon and catecholamines

30
Q

other effects of cortisol

A

weak mineralocorticoid effects

renal and cardiovascular effects - excretion of water load, increased vascular permeability

31
Q

how is cortisol secretion regulated - ACTH

A

negative feedback at 2 levels

32
Q

effects of ACTH on the adrenal glands

A 
activation of these enzymes
side chain cleavage 
3 beta hydroxysteroid dehydrogenase
17 hydroxylases
21 hydroxylases
11 hydroxylases
33
Q

what rhythm does cortisol have

A

diurnal and circadian

34
Q

what is addisons disease

A

primary adrenal failure
an autoimmune disease where the immune system decides to destroy the adrenal cortex
tuberculosis of the adrenal glands
the pituitary starts secreting lots of ACTH and hence MSH (melanocyte stimulating hormone?) > increased pigmentation > autoimmune vitiligo may coexist
no cortisol or aldosterone > low blood pressure
cortisol and aldosterone deficiency
salt loss
low BP eventual death

35
Q

symptoms and signs of addisons

A 
hyperpigmentation
low bp
weakness
weight loss
gastrointestinal (nausea, diarrhoea, vomiting, constipation, abdominal pain)
vitiligo
36
Q

what does an addisonian/adrenal crisis consist of

A 
fever
syncope (fainting)
convulsions
hypoglycaemia
hyponatremia - low sodium
severe vomiting and diarrhoea
37
Q

what is POMC

A

pre-opio melanocortin
a large precurosor protein that is cleaved to form a number of smaller peptides - ACTH, MSH and endorphins
so people with pathologically high ACTH may become tanned

38
Q

urgent treatment of addisonian crisis

A

rehydrate with normal saline
give dextrose (glucose) to prevent hypoglycaemia which could be due to glucocorticoid deficiency
give hydrocortisone or another glucocorticoid

39
Q

what is Cushings syndrome

A

too much cortisol due to adrenal tumour or tumour of pituitary (more ACTH)
cortisol inhibits protein synthesis
excess cortisol or other glucocorticoid

40
Q

causes of Cushings syndrome

A

taking steroids by mouth (common) - asthmatics
pituitary dependent cushings disease (pituitary adenoma)
ectopic ACTH (lung cancer) - wrong place
adrenal adenoma or carcinoma (tumour)

41
Q

symptoms and signs of Cushings

A 
moon face
red cheeks
fat pads - buffalo hump
mental changes eg depression
thin skin
easy bruising
impaired glucose tolerance (diabetes)
high blood pressure
proximal myopathy (muscle weakness)
thin arms and legs
red striae
pendulous abdomen
poor wound healing
42
Q

what is the role of catecholamines

A

fight or flight response

tachycardia, sweating, increased blood glucose, alertness, vasoconstriction

43
Q

how does NA and A circulate in the blood and what is it degraded by

A

bound to albumin

degraded by 2 hepatic enzymes - monoamine oxidase and catechol-O-methyl transferase

44
Q

where is the adrenal medulla derived from

A

ectodermal neural crest

45
Q

what is the precursor for NA and Adr synthesis

A

tyrosine

46
Q

where are catecholamines stored

A

in cytoplasmic granules and released in response to ACh from preganglionic sympathetic neurones

47
Q

how is dopamine made

A

tyrosine is oxidised to dopa

dopa is oxidised to dopamine

48
Q

how is dopamine made

A

tyrosine is oxidised to dopa

dopa is oxidised to dopamine

49
Q

where does adrenaline come from

A

dopamine

by oxidation and then methyl addition to become epinephrine

bioregulatory systems 🦠 (54 decks)

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