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ESA 2 - MEH > 9. The adrenal glands > Flashcards

9. The adrenal glands Flashcards

1
Q

Where are the adrenal glands located?

A

cap upper poles of kidneys and lie against diaphragm in retroperitoneal space

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2
Q

name the 2 regions of the adrenal glands

A

outer CORTEX

inner MEDULLA

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3
Q

which hormones does the adrenal cortex produce?

A

The deeper the sweeter:

  1. zona glomerulosa:
    - mineralocorticoids (e.g. ALDOSTERONE)
    - regulate body Na+ and K+ levels
    - salt
  2. zona fasiculata:
    - glucocorticoids (e.g. CORTISOL)
    - many important functions inc. regulation of carbohydrate metabolism
    - sugar
  3. zona reticularis:
    - glucocorticoids and small amount of ANDROGENS
    - sex
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4
Q

what happens to the androgens released by the AGs?

A

converted to testosterone and oestrogens by other tissues

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5
Q

which hormones does the adrenal medulla produce?

A

chromaffin cells synthesise ADRENALINE (80%) and NORADRENALINE (20%)

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6
Q

what are steroid hormones synthesised from?

A

cholesterol (in AGs and gonads)

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7
Q

name the 5 major types of steroid hormone

A
  1. glucocorticoids
  2. mineralocorticoids
  3. androgens
  4. oestrogen
  5. progesterone
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8
Q

what is the MOA of steroid hormones?

A

lipid soluble hormones that bind to receptors of the nuclear receptor family to modulate gene transcription

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9
Q

describe how glucocorticoids modulate gene transcription

A

i. diffuse across plasma membrane…
ii. bind to and activate glucocorticoid receptors by causing dissociation of chaperone proteins (e.g. heat shock protein 90)…
iii. receptor-ligand complex translocates to nucleus…
iv. dimerisation with other receptors can occur…
v. receptors bind to glucocorticoid response elements (GREs) or other transcription factors

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10
Q

What is the primary mineralocorticoid?

A

aldosterone

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11
Q

What is the primary glucocorticoid hormone?

A

cortisol

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12
Q

Which hormones does the zona reticularis secrete?

A

weak androgens: DHEA and androstenedione

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13
Q

How is adrenal release of androgens controled?

A

partially regulated by ACTH and CRH

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14
Q

What happens to DHEA in males?

A

converted to testosterone in testes (after puberty this is insignificant since testes release far more testosterone themselves)

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15
Q

What is the role of adrenal androgens in females?

A

converted to oestrogen by other tissues (only source after menopause). promotes libido.

promotes axillary and pubic hair growth in both sexes

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16
Q

What type of cells does the adrenal medulla consist of?

A

adrenal medulla = modified sympathetic ganglion of ANS

- chromaffin cells lack axons but act as post-ganglionic nerve fibres that release hormones into blood

17
Q

which 2 hormones are released by the adrenal medulla?

A

ADRENALINE (80%)

NORADRENALINE (20%) - 20% chromaffin cells lack N-methyl transferase enzyme

18
Q

Name 2 precursors of Ad and NA.

A

tyrosine and dopamine

19
Q

Describe the receptor subtypes of Ad and NA.

A

act at adrenergic receptors = GPCRs

  1. alphaRs
    • alpha1: increase in intracellular Ca2+ via coupling to Galpha q
    • alpha2: decrease in intracellular cAMP via coupling to Galpha i
  2. betaRs
    • beta1, 2 and 3: increase in intacellular cAMP via coupling to G alpha s
20
Q

What are the main actions of adrenaline?

A

fight or flight

  1. cardiovascular system
    • increase HR and contractility (B1)
    • vasoconstriction to skin/gut (a1)
    • vasodilation to skeletal muscle (B2)
  2. lungs
    • bronchodilation (B2)
  3. carbohydrate metabolism
    • increase glucagon and decrease insulin secretion from pancreas
    • increase glycolysis and glycogenolysis in muscle
    • increase glycogenolysis and gluconeogenesis in liver
  4. lipid metabolism
    • increase lipolysis in adipose
  5. other
    • increase mental alertness
    • increased renin secretion in kidney
21
Q

Describe how adrenaline increases HR.

A

activates B1 GPCR…GDP for GTP exchange at G protein… alpha s-GTP activates AC… conversion of ATP to cAMP… 4 cAMP activate PKA.

  1. direct activation by cAMP of HCN channels resposible for funny/pacemaker current
  2. PKA phosphorylation of HCN channels modulates function
  3. PKA phosphorylation of L-type Ca2+ channels - potentiates opening, increasing slope of upstroke of AP
22
Q

Compare the 2 main types of hormones released by the adrenal glands: corticosteroids and catcholamines.

A

CORTICOSTEROIDS (cortisol, aldosterone, androgens)

1) synthesised in cortex
2) derived from cholesterol
3) endocrine
4) lipid soluble
5) nuclear Rs - regulate gene expression
6) slow resp (min-hrs)

CATECHOLAMINES (Ad and NA)

1) synthesised in medulla
2) derived from tyrosine
3) neurocrine
4) water soluble
5) GPCRs - regulate activity of existing enzymes
6) fast resp (secs)

ESA 2 - MEH (42 decks)

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