adrenals

Question 1

glucocorticoid synthesis: backbone molecule

Answer 1

synthesised from cholesterol in same way as pituitary

Question 2

glucocoticoid synthesis: diversity

Answer 2

different enzymes in different cortex regions causes different hormones such as cortisol or aldesterone produced

Question 3

aldosterone vs cortisol

Answer 3

remove one enzyme and replace with another downstream; pregnenolone diverted to progesterone in aldosterone synthesis

Question 4

how are steroid hormones transported in blood

Answer 4

lipid soluble so rapidly diffuse into blood; weak binding to proteins in blood or strong binding to specific binding proteins e.g. CBG (cortisol binding globulin)

Question 5

% cortisol unbound

Answer 5

10%

Question 6

% aldosterone unbound

Answer 6

40%

Question 7

cortisol in blood

Answer 7

higher levels in morning than evening

Question 8

aldosterone in blood

Answer 8

1000-fold decrease vs cortisol

Question 9

which receptors do cortisol bind to

Answer 9

glucorticoid receptors and aldosterone (mineralcorticoid) receptors

Question 10

which receptor does aldosterone bind to

Answer 10

aldosterone (mineralcorticoid) receptors

Question 11

function of 11bhsd2 enzyme

Answer 11

breaks down cortisol

Question 12

why is aldosterone relevant

Answer 12

some tissues have high levels of 11bhsd2 enzyme so only aldosterone can enter and influence activity

Question 13

what tissues have high 11bhsd2 levels

Answer 13

kidneys, placenta

Question 14

define renin-angiotensin system

Answer 14

hormone system that regulates blood pressure and fluid balance in kidney (nephron)

Question 15

what cells produce renin

Answer 15

granular cells

Question 16

what factors increase renin production

Answer 16

low renal blood pressure, increase in renal sympathetic nervous activity, macular densa cells in distal convoluted tubule acting as Na+ sensors: if low Na+ renin production increases

Question 17

renin function

Answer 17

allows reabsorbtion Na+, therefore H2O reabsorbed, therefore blood pressure restored

Question 18

what protein does renin activate and what does this produce

Answer 18

angiotensinogen producing angiotensin I

Question 19

what does ACE do in the lungs

Answer 19

converts angiotensin I to angiotensin II

Question 20

function of angiotensin II

Answer 20

stimulates aldosterone production in zona glomerulosa

Question 21

what also stimulates aldosterone production

Answer 21

low Na+ and K+ levels

Question 22

how is homeostatic control ensured

Answer 22

hypothalamo-pituitary-adrenal axis

Question 23

aldosterone mechanism of action: location

Answer 23

acts on late distal tube and collecting duct

Question 24

aldosterone mechanism of action

Answer 24

aldosterone causes reabsorption of Na+ → creates more Na+ ion channels → Na+ diffuses through Na+ ion channel in tubule lumen endothelium down conc gradient → to ensure conc. gradient, aldosterone increases number of Na+/K+ ATPase pumps in blood endothelium → more Na+ reabsorbed and K+ exchanged into tubule lumen → more H2O reabsorbed also

Question 25

cortisol mechanism of action

Answer 25

binds to glucorticoid receptor in cell, influences transcription of specific proteins in nucleus

Question 26

MR and GR activation for maximal effects in normal physiology and stressful physiology

Answer 26

full MR activation and partial GR activation; both full when under stress

Question 27

cortisol effect on glucose

Answer 27

stress hormone so ensures glucose readily available and lots of stores of glucose; increases gluconeogenesis and glycogenesis; decrease glucose from entering storage sites in skeletal muscle or fats; prevents fatty acids staying in adipocytes; decreases blood flow, decreases GLUT 4

Question 28

cortisol: physiological actions

Answer 28

pro-memory at dentate gyrus in hippocampus: serotonin innervation promotes granule cell division and memory formation; cortisol upregulates serotonin 5HT 1A receptors

Question 29

cortisol: supra-physiological actions

Answer 29

promotes anti-inflammatory and immunosuppressive effects; anti-memory effects if chronic stress as hippocampus destroyed by cortisol, impacting long-term memory formation

Question 30

adrenal androgens

Answer 30

sex steroids, weak biological activity but converted to more active androgens by enzymes in peripheral tissues

Question 31

define steroid

Answer 31

hormone which precursor is cholesterol (C27, 4 rings)

Question 32

how is cholesterol converted to cortisol

Answer 32

cholesterol → progesterone → 17-OH-progesterone → 11-deoxycortisol → cortisol

Question 33

how is cholesterol converted to aldosterone

Answer 33

cholesterol → progesterone → 11-deoxy-corticosterone → corticosterone → aldosterone