regulation of adrenocortical steroidogenesis W6

Question 1

cholesterol structure?

Answer 1

HO group (polar head group)
steroid body (4 rings)
hydrophobic side-chain

Question 2

cholesterol as a component of cell membranes?

Answer 2

aligns between membrane phospholipids
attracted to polar head and hydrophobic tail

Question 3

what are steroids soluble in

Answer 3

steroids are fat soluble

Question 4

2 main types of steroid hormones? where are they made?

Answer 4

corticosteroids (cortex of adrenal gland)
sex steroids (made in gonads)

Question 5

types of corticosteroids?sa

Answer 5

mineralocorticoids
glucocorticoids
adrenal androgens

Question 6

mineralocorticoids function?

Answer 6

salt and water retention

Question 7

glucocorticoids function

Answer 7

glucose synthesis
protein and lipid metabolism
inflammation, immune response

Question 8

adrenal androgens function?

Answer 8

fetal steroids and growth

Question 9

3 types of sex steroids?

Answer 9

androgens
oestrogens
progesterones

Question 10

what is vitamin D?

Answer 10

steroid hormone

Question 11

key adrenal steroid hormones? structural differences?

Answer 11

aldosterone (O, CH, OH)
cortisol (OH)
androstenedione (O)

Question 12

what distinguishes a glucocorticoid from other steroids?

Answer 12

11 beta hydroxylase group (?)

Question 13

steroid hormones mechanism of action (classic ‘genomic’)

Answer 13

circulating steroid hormones bind to hormone receptors in cytoplasm, makes active transcription complex that acts on DNA in nucleus creating mRNA that causes protein synthesis in cytoplasm

Question 14

how long do steroid hormones take to act?

Answer 14

30 mins - 48 hrs

Question 15

‘non-genomic’ mechanism of steroid hormones?

Answer 15

receptors such as ion channels in plasma membrane activated directly by steroid binding

Question 16

‘non-genomic’ mechanism of steroid hormones time to act?

Answer 16

<1m

Question 17

how are steroid hormones made from cholesterol?

Answer 17

hydrophobic 6 carbon side chain removed
varied substituent at C-17
Extra specificity from side chain modification eg C-11

Question 18

2 types of enzymes involved in steroid synthesis?

Answer 18

cytochrome P450s (CYPs)
steroid dehydrogenases/reductases

Question 19

where are cytochrome P450s highly expressed?

Answer 19

liver (drug detoxification)
organs that synthesize steroids (adrenal cortex, testis, ovary, placenta)

Question 20

function of cytochrome P450s?

Answer 20

cleave or modify cholesterol side groups

Question 21

function of steroid dehydrogenases/reductases?

Answer 21

interconvert active and inactive forms of steroid

Question 22

cortisol inactive form?

Answer 22

cortisone

Question 23

what steroid dehydrogenase/reductase converts cortisol to cortisone and vice versa?

Answer 23

11β-HSD1 and 11β-HSD2

Question 24

cortisol pathways?

Answer 24

released from adrenal gland into circulation, 90%+ binds to transport protein and affects target tissues.
some cortisol recycles through liver, converted to cortisone which circulates and reaches target tissues where it is reactivated by 11β-HSD1

Question 25

what do the adrenal glands do!

Answer 25

coordinates the bodies response to internal physiology and environmental stimuli

Question 26

where are the adrenal glands located?

Answer 26

around 12th thoracic vertebra positioned bilaterally and anteriorly above kidneys

Question 27

anatomists name for adrenal glands?

Answer 27

suprarenal glands

Question 28

2 endocrine axes that adrenal glands play a role in?

Answer 28

hypothalamic-pituitary-adrenal (HPA) axis neuroendocrine sympathetic nervous system

Question 29

which part of the adrenal glands is involved in the HPA axis

Answer 29

adrenal cortex

Question 30

which part of the adrenal glands is involved in the neuroendocrine sympathetic nervous system

Answer 30

adrenal medulla

Question 31

function of adrenal cortex?

Answer 31

makes steroid hormones

Question 32

adrenal medulla function?

Answer 32

extension of sympathetic nervous system makes catecholamines

Question 33

blood supply to adrenal cortex?

Answer 33

short arteries penetrate the capsule, supply a subcapsular plexus of arterioles capillary sinusoids extend through the cortex separating chords of cells this structure allows rapid transmission of stimuli to cells and products to targets

Question 34

adrenal medulla blood supply?

Answer 34

receives long cortical arteries and capillaries from cortex

Question 35

adrenal medulla and cortex venous drainage?

Answer 35

drain via central and medullary vein

Question 36

zones of adrenal cortex?

Answer 36

zone glomerulosa zona fasciculata zona reticularis

Question 37

where is aldosterone made

Answer 37

zona glomerulosa

Question 38

what is aldosterone under control of

Answer 38

RAS (renin-angiotensin system)

Question 39

what does aldosterone regulate

Answer 39

salt and water retention in kidney distal tubule

Question 40

aldosterone is the principle what?

Answer 40

aldosterone is the principle mineralocorticoid in humans

Question 41

cortisol is the principle what?

Answer 41

cortisol is the principle glucocorticoid in humans

Question 42

where is cortisol made

Answer 42

zona fasciculata

Question 43

what is cortisol under control of

Answer 43

HPA axis

Question 44

what does cortisol regulate?

Answer 44

glucose homeostasis stress response inflammation immune response

Question 45

where are C19 adrenal androgens made

Answer 45

zona reticularis

Question 46

what are C19 adrenal androgens under control of

Answer 46

HPA axis

Question 47

C19 adrenal androgens function?

Answer 47

intracrine conversion to testosterone and oestradiol in peripheral tissues prenatal and postnatal DHEA production

Question 48

positive regulators of CRH (cortisol releasing hormone)

Answer 48

serotonin acetylcholine encephalin

Question 49

negative regulators of CRH (cortisol releasing hormone)

Answer 49

alpha-adrenergic agonists GABA, endorphin dopamine

Question 50

circadian rhythm of CRH release?

Answer 50

CRH high in early morning (4-8) and lower later in day CRH regulates ACTH release ACTH high on waking (6-10) and lowest in middle of night

Question 51

what are corticotropes

Answer 51

cells in anterior pituitary that release ACTH, MSH and lipotropin

Question 52

homeostatic feedback regulation of cortisol synthesis by the HPA axis?

Answer 52

circadian rhythm and stress inputs stimulate CRH release from hypothalamus CRH stimulates ACTH production from pituitary corticotrophs ACTH stimulates cortisol production from adrenal zona fasciculata cortisol feeds back on release of CRH from hypothalamus and ACTH from the anterior pituitary

Question 53

StAR protein function?

Answer 53

steroid acute regulatory protein sits in membrane of mitochondria and promotes transport of cholesterol from cytoplasm into mitochondria where steroid hormones are made crucial regulatory step!!

Question 54

what hormone levels rise as plasma glucose falls?

Answer 54

glucagon adrenaline noradrenaline growth hormone cortisol

Question 55

dual action of cortisol?

Answer 55

anabolic in liver to promote gluconeogenesis catabolic in peripheral muscle and fat to promote protein and lipid breakdown

Question 56

anabolic actions of cortisol?

Answer 56

increased gluconeogenesis and liver glucose output

Question 57

catabolic actions of cortisol?

Answer 57

inhibition of glucose uptake by peripheral muscle fat and tissue immune system suppression increased muscle protein breakdown increased fat breakdown increased bone resorption increased appetite and central fat deposition

Question 58

pathophysiological actions of cortisol - anabolic?

Answer 58

elevated plasma glucose - secondary diabetes mellitus

Question 59

pathophysiological actions of cortisol - catabolic?

Answer 59

muscle and connective tissue wasting and weakness poor wound healing and skin ulcers uncontrolled muscle protein breakdown increased fat redistribution osteoporosis uncontrolled appetite and central fat deposition excess mineralocorticoid action = Na+ and fluid retention and hypertension

Question 60

disease of cortisol excess?

Answer 60

Cushing's Disease

Question 61

Cushing's disease - features

Answer 61

hypertension low plasma K+ elevated plasma cortisol low plasma aldosterone and renin activity.