Adrenals and corticosteroids

Question 1

where are the adrenal glands

Answer 1

above the kidneys

Question 2

layout of the adrenal gland

Answer 2

inside = medulla
outside = cortex
anything from cortex has to drain through medulla into tributary of central vein

Question 3

describe the blood vessels of the adrenal glands

Answer 3

L adrenal gland vein - renal vein - vena cave
R - vena cava
one vein to secrete hormones into the blood
both have many arteries though - to supply the kidney’s with the blood that they need

Question 4

parts of the cortex from outside in and the hormones they make

Answer 4

tough, fibrous capsule
zona glomerulosa - aldosterone (mineralocorticoids)
zona fasciculata and zona reticularis - cortisol (glucocorticoids)
cortex also make sex steroids - androgens and oestrogens

Question 5

what hormones does the medulla make

Answer 5

catecholamines

- adrenaline, noradrenaline

Question 6

describe the synthesis of steroid hormones

Answer 6

all from cholesterol
mineralocorticoids and glucocorticoids - C21. in sex hormones more is cleaved off the backbone
lipoprotein deliver cholesterol
fat droplets in esters
signal cause esterase to relieve cholesterol from esters
StAR protein takes cholesterol into the mitochondria
the enzymes to make the hormone are different in different parts of the cortex

Question 7

difference in the pathway of aldosterone and cortisol production

Answer 7

in aldosterone production 1 enzyme is removed making progesterone
1 enzyme is added making aldosterone from corticosterone which is inactive on its own

Question 8

why are there only a few sex steroids

Answer 8

the enzymes for their synthesis are extra so are at low levels

Question 9

describe the storage of steroid hormones

Answer 9

lipid soluble - don’t stay in cell long
protein store for hormone
albumin/CBG (corticosteroid binding globulin)
90% of cortisol is protein bound, 60% of aldosterone is protein bound

Question 10

effect of hormones being relieved from proteins

Answer 10

if high proportion of the protein is bound - small decrease in binding has a large effect

Question 11

what are the concentrations of the steroid hormones

Answer 11

cortisol level is diurnal - change throughout the day and 1000x higher than aldosterone always

Question 12

corticosteroid receptors

Answer 12

glucocorticoid receptors (GR) 
aldosterone receptors (MR)

Question 13

which receptor does aldosterone use

Answer 13

MR

Question 14

which receptor does cortisol use

Answer 14

GR and MR

not specific

Question 15

what makes aldosterone useful if it is in such low qunatities and only has 1 receptor

Answer 15

the enzyme 11b-hydoxysteroid dehydrogenase 2 is a cortisol metabolising enzyme - break cortisol into cortisone - inactive
kidney and placenta (stop maternal cortisol getting at foetus) protected from cortisol so still need aldosterone

Question 16

what increases renin production

Answer 16

low Na conc
renal perfusion pressure decrease
increase in renal sympathetic activity

Question 17

where is renin produced

Answer 17

granular cells in kidney

Question 18

describe how the renin-angiotensin system is linked to aldosterone secretion

Answer 18

macular densa cells sense Na drop in fluid in kidney
stimulates renin production
Increases Na reabsorbtion and so water - maintains Bp (low Bp shown by low RPP)
renin is enzyme number 1, activates angiotensinogen to angiotensin 1
lung have a lot of angiotensin converting enzyme (ACE) – angiotensin II
stimulates production of aldosterone in adrenalcortico gland

Question 19

other stimuli for aldosterone synthesis

Answer 19

increased K+

decreased Na+

Question 20

describe the stimulus of cortisol

Answer 20

hypothalamic hormone - corticotrophin releasing hormone - act on anterior pituitary gland corticotrophs
releases adrenocorticotropin (ACTH) act on adrenal cortex
cortison produced

Question 21

how is cortisol production controlled

Answer 21

-ve feedback

Question 22

what happens in the kidney

Answer 22

electrolytes are reabsorbed

Question 23

describe the physiological effect of aldosterone

Answer 23

act in kidney
late distal tubule/collecting duct
Na is driven into DCT then into the blood
Na channel at lumen - Na enters by diffusion if concentration gradient
Na/K ATPase makes sure there is a conc gradient as Na is removed into the blood
some K is lost
aldosterone is slow acting, it increases the number of Na channels and ATPases ie it upregulates the ability to absorb Na
allows water to diffuse through DCT as it provides an osmotic gradient

Question 24

describe the generic action of cortisol

Answer 24

it binds to the GR receptor and changes protein transcription and translation

Question 25

why is the mechanism of cortisol complex

Answer 25

which receptor is relevant to which effect there are optimal levels of activation ideally it heavily binds to MR and partially binds to GR - activation in times of stress there is acute GR activation - convert back to normal as quick as possible

Question 26

describe cortisol's effect on metabolism

Answer 26

makes sure that glucose is readily available and that glucose stores are full in liver increases gluconeogenesis and allow liver to generate glucose at max capacity increase enzymes that allow glucose to be stored as glycogen stop glucose being stored peripherally - inaccessible reduce blood flow to tissues stop glucose/fatty acid being stored in skeletal muscle/adipose tissue the effect of this is maximal in sleep

Question 27

describe cortisol and memory physiologically

Answer 27

promemory imprint memory for survival the dante gyrus in the hippocampus is where memories are produced serotonin promotes memory formation - promotes granule cell division cortisol makes more serotonin 5HT 1A receptors serotonin makes the hippocampus more sensitive to cortisol. cortisol - positive effect on serotonin and serotonin upregulates the memory

Question 28

describe cortisol's action as an anti-inflammatory/immunosuppressive

Answer 28

homeostatic - turn of inflammatory response released to dampen down inflammation in supra-physiological actions cortisol not part of the feedback loop - continually roduced in stress cortisol constantly suppressing immune system - more susceptible to disease

Question 29

what increases the cortisol levels

Answer 29

caffeine and alcohol

Question 30

how does cortisol have supra-physiological actions for memory

Answer 30

if have chronically high cortisol excessive GR activation - negative effect on serotonin hippocampus gets smaller inhibit the ability for long term memory formation

Question 31

describe adrenal androgens

Answer 31

synthesised in zona reticularis dehydroepiandrostenedione DHEAS and androstenedione weak biological activity - converted to more active androgens eg testosterone by enzymes in peripheral tissue women -adrenal production of DHEA and DHEA-S contributes substantially to overall androgen production and effects men - the adrenal contribution to androgen is very small if adrenal cortex is over active - enough sex hormone is produced to have an effect