The Adrenal gland Flashcards
structure of the adrenal gland
- 2 adrenal glands located on the superior poles of the kidneys
- 10g in mass
- Form a pyramidal shape
layers of the adrenal gland
capsule + cortex + medulla
capsule
fibrous layer on the outside of the adrenal gland
the adreanl cortex is made up of 3 layers called:
(GFR)
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
Zona glomerulosa secretes
mineralcorticoids
Zona fasciculata
Glucocorticoids
Zona reticularis
Glucocorticoids and small amount of androgens (sex)
name the mineralcorticoid secreted by the zona glomerulosa
Aldosterone- Salt
name the glucocorticoid secreted by the zona fasciculata
cortisol- sugar
name the androgens released by the zona reticularis
oestorgen and testosterone
how to remeber cortex layers
GFR: Salt Sugar Sex
the deeper you get the sweeter it gets
medulla is made up of
chromaffin cells- neural crest cells
- part of the sympathetic immune system
what does the medulla release
adrenaline and noradrenaline (20%)
all the hormones released by the 3 layers of the medulla are
corticosteroids
steroid horemones are synthesised from
cholersterol in the adrenal glands and gonads
features of steroid hormones
- Lipid soluble (intracellular receptors)
- Bind to receptors of the nucleus to modulate gene transcription
outline how corticosteroids exert their actions by regulating gene transcription
- Corticosteroids readily diffuse across the plasma membrane
- Binds to the glucocorticoid receptor
- Binding causes dissociation of chaperone protein
- Receptor ligand complex translocate to the nucleus
- Dimerization with other receptors can occur
- Receptor binds to glucocorticoids response elements (GRE) (DNA) or other transcription factors
Aldosterone (mineralocorticoid)
- Zona Glomerulosa
- Most abundant mineralocorticoid
- Synthesis and released by adrenal cortex
- Steroid hormone= lipophilic (intracellular receptro)
how is aldosterone transported in the blood
Carrier protein = mainly serum albumin and to a lesser extent transcortin
role of alsoterone
- Regulation of plasma Na+, K+ and arterial blood pressure
- Main action in distal tubules and collecting ducts
- Promotes expression of Na+/K+ pump promoting reabsorbing of Na+ and excretion of K+à water retention, blood volume and therefore blood pressure (RAAS)
main disorders associated with aldoseronehyperaldosteronism and hypoaldosteronism
Cortisol (corticosteroid)
- Zona fasciculata
- Most abundant corticosteroid and accounts for 95% pf glucocorticoid activity
- Synthesised and released in response to ACTH (Adrenocorticotropic hormone)
- Negative feedback to hypothalamus inhibits CRH and ACTH release
- Steroid hormone
carrier protein of cortisol
transcortin
actions of cortisol (6)
- Increased protein breakdown in muscle
- Increased lipolysis in fat
- Redistribution of fat e.g. buffalo hump- dorso-cervical fat pad
- Increase gluconeogenesis- increases glucose- in the liver
- Resistance to stress (increased supply of glucose, raise blood pressure by making vessels more sensitive to vasoconstrictors)
- Anti-inflammatory effects (inhibits macrophage activity and mast cell degranulation)
- Depression of immune response (prescribed to organ transplant patients)
net effect of cortisol
- Increased glucose production
- Increase glucose leads to increase insulin so liver increase glycogen stores
- Breakdown of protein
- Cortisol inhibits insulin-induced GLUT4 translocation in muscle (prevents glucose uptake so has glucose sparing effect)
- Redistribution of fat (buffalo hump)
- Chronic high levels of cortisol results in re-distribution of fat especially in the abdomen, supraclavicular fat pads and dorso-cervical fat pad (buffalo hum) and
main disorders associated with cortisol
- Cushings syndrome (excessive exposure to cortisol)
- Addisons disease (insufficient cortisol)
- Addisonian crisis (insuffieinet cortisol)
androgens
- Zona reticularis- inner most layer
- Secretes dehydroepiandrosterone (DHEA) and androstenedione (weak androgens)
- Partially regulated by ACTH and CRH
in male DHEA is converted to
testosterone in the testes
in females adrenal adrogens are converted to
oestorgen by other tissues
(after menopause only source of oestorgen is from the adrenal glands- no more from ovaries)
androgens promote
libido (women) and axillary/public hair growth (both sexes)
the cells in the adrenal medulla acts as
Acts as a modified sympathetic ganglion of the ANS
Chromaffin cells in adrenal medulla lack axons but
acts as postganglionic nerve fibre that release hormones into blood
adrenalien and NA are devived from
tyrosine
outline production of A and NA dfrom tyrosine
Tyrosine –> levodopa –> dopamine –> NA–> A
~20% chromaffin cells lack N-methyl transferase enzyme and secrete noradrenaline
features of NA and A
- Water soluble –> binds to outside of the cell
- Signal via GPCRs (alpha and B)
- Fast (seconds)
hormonal action of adrenaline
fight or flight response- affects mltiple organs
adrenaline action on the heart
increase heart rate and contractility (B1)
adrenaline action on the lungs
bronchodilation (B2)
adrenaline action on the blood vessels
- the skin and gut
- skeletal muscle
- the skin and gut
- vasoconstriction (alpha 1)
- Skeletal muscle
- vasodialtion (B2)
adrenaline action on the kidney
increased renin secretion (B1,B2)
Pheochromocytoma (chromaffin cell tumour)
Phae= dark
Chromo= colour
Cyte= cells
Oma= tumour
- Rare, catecholamine-secreting tumour (mainly NA)
- May precipitate life-threatening hypertension
symptoms of pheochromocytoma
- Severe hypertension
- Headaches
- Palpitations
- Diaphoresis (excessive sweating)
- Anxiety
- Weight loss
- Elevated blood glucose
the cortex secretes….. whislt the medulla secretes
cortex- corticoids (cortisol, aldosreorne, androgens)
medulla- catecholaminesn (NA/A)
