adrenal gland physiology Flashcards
how many adrenal glands are there
2
where are the adrenal glands
one above each kidney
what are the adrenal glands composed of
two endocrine organs one surrounding the other
what does the outer layer of adrenal gland compose
adrenal cortex
what does the adrenal cortex secrete
steroid hormones
what are the inner parts of the adrenal glands
adrenal medulla
what does the adrenal medulla secrete
catecholamines
what are the 3 layers of the adrenal cortex
- zona glomerulosa - zona fasciculata - zona reticularis
what is the outer layer of the adrenal cortex
zona glomerulosa
what is the middle layer of the adrenal cortex
zona fasciculata
what is the inner most layer of the adrenal cortex
zona reticularis
what does the adrenal cortex produce
a number of different adrenocortical hormones
what are all steroids derived from
cholesterol
what is the main mineralocorticoid
aldosterone
what is the main glucocorticoid
cortisol
what does cortisol play a major role in
glucose metabolism
what are sex hormones similar to
similar to those produced by the gonads (testes in males, ovaries in females)
what part of the adrenal cortex produces aldosterone
zona glomerulosa
where is cortisol synthesised
limited to the two inner layers of the adrenal cortex
where is the major source of glucocorticoid
zona fasciculata
are the adrenocortical hormones lipophilic
yes
how are the adrenocortical hormones carried
in the blood bound to plasma proteins
what is cortisol bound to mostly
plasma protein corticosteroid-binding-globulin
what is aldosterone mostly bound to
albumin
does each adrenocorticol steroid hormone bind to its own specific hormone
yes
where is the principle site of aldosterone action
distal and collecting tubules of the kidney
what is the effect of aldosterone
promotes sodium retention and enhances potassium elimination during the formation of urine
what does cortisol play an important role in
- carbohydrate, protein and fat metabolism - hormonal activities - helps resist stress
what is the overall effect of cortisol metabolically
increase the concentration of blood glucose at the expense of protein and fat stores
cortisol and gluconeogenesis
stimulates it
cortisol and glucose uptake
inhibits glucose uptake - but not in the brain
cortisol and lipolysis
facilitates it - releasing fatty acids
what is cortisol important for
permit the catecholamines to induce vasoconstriction - if lacking cortisol a patient may go into shock in a stressful situation that demands vasoconstriction
what does cortisol play a key role in
stress
cortisol and the immune system
- anti-inflammatory - immunosuppressive
what inflammatory mediators does cortisol partially block
- prostaglandin - leukotrienes
how does cortisol affect the neutrophils
suppresses migration of neutrophils to the site of inflammation
what can lymphocytes secrete
ACTH
cortisol and the immune system
dampens its affects
what can be administered to inhibit the inflammatory response
glucocorticoids
what are glucocorticoids good at treating
rheumatoid arthritis
how should glucocorticoids be administered
sparingly
why should glucocorticoids be given sparingly
- patient has limited ability to resist infection - troublesome side effects - suppresses the hypothalamus
side effects of glucocorticoids
- GI ulcers - high blood pressure - atherosclerosis - menstrual irregularities - bone thinning
REGULATION OF CORTISOL
REGULATION OF CORTISOL
what secreted cortisol
adrenal cortex
how is secretion of cortisol regulated
negative feedback
what tare the steps of cortisol secretion
- ACTH from anterior pituitary corticotropes 2. acts through cAMP 3. stimulates the adrenal cortex to secrete cortisol
what happens when ACTH is reduced
the zona fasciculata and zona reticualris shrink considerably and cortisol secretion is reduced
what maintains the size of the zona glomerulosa
angiotensin
what enhances the synthesis of cortisol
ACTH
specific influences of ACTH on cortisol production
- ACTH mobilises cholesterol from the lipid droplets in the zona fasciulata and reticularis 2. increases the production of pregneneolone from cholesterol 3. increases production of enzymes needed to convert pregneolone into cortisol
what causes ACTH release
corticotropin-releasing hormone (CRH) from the hypothalamus
how does CRH stimulate corticotropes
via cAMP
what 2 factors influence cortisol concentration
- diurnal rhythm - stress
what kind of rhythm does cortisol display
diurnal rhythm
when is the highest level of cortisol
morning
when is the lowest level of cortisol
night
what increases cortisol level
stress
HORMONES
HORMONES
what does adrenal cortex produce in females
estrogens
what does adrenal cortex produce in males
androgens
where is the main site of production of sex hormones
gonads - testes males - ovaries females
does each sex only produce their specific hormones
no they both have a small amount of the other
what converts testosterone into oestrogen
aromatase
where is aromatase found
adipose tissue
what is the only adrenal sex hormone that has biological importance
androgen dehydroepiandrosterone (DHEA)
does ACTH control adrenal gland androgen secretion
yes
ADRENAL CONDITIONS
ADRENAL CONDITIONS
what hormones can be overstimulated
- aldosterone - cortisol - adrenal
what can cause excessive mineralocorticoid secretion
- hyper-secreting adrenal tumour - inappropriately high activity of renin angiotensin aldosterone system
example. of excess mineralocorticoid secretion diseases
- atherosclerotic narrowing of renal arteries
symptoms of hyperaldosteronism
- hypernatremia (Na+ retention) - hypokalaemia (K+ depletion) - hypertension
what is cortisol hypersecretion call
Cushings syndrome
what can cause Cushings syndrome
- overstimulation of adrenal cortex by excessive amounts of ACTH - adrenal tumours that secrete cortisol - ACTH secreting tumours located in places other than the pituitary
what are the symptoms of Cushings caused by
exaggerated effects of glucocorticoids
what happens when too many amino acids are converted into glucose
high blood glucose (mimics diabetes mellitus)
where is the extra glucose deposited
- as body fat - abdomen - above shoulder blades - face
what are the excess glucose depositions called
- buffalo hump - moon face
what does loss of muscle protein lead to
muscle weakness and fatigue
what does loss of structural protein in blood vessels lead to
easy bruisability
what is adrenal androgen secretion condition
masculinising condition
what do androgen exert
masculinising effects
what happen when a women has androgen secretion
develop male pattern of body hair
what is it called when a women has a male pattern body hair
hirtuism
what are other symptoms of androgen secretion
- deepening of the voice - muscular arms and legs - smaller breast - menstruation may cease
what happens if a newborn female has adrenogenital syndrome
they have male type external genitalia
why do newborn females get male genitalia
as the clitoris enlarges under androgen influence and takes on a penile appearance
what is it called when the female ovaries are present but the external genitalia resemble those of a male.
female psueodhermaphroditism
what is it when pre pubertal males have excessive androgen secretion
- deep voice - beard - enlarged penis - sex drive
what is it called when a pre pubertal male has excessive androgen
precocious pseudopuberty
in pseudopuberty do the males develop sperm
no as the testes are still in their non-functional prepubertal state
does excess androgen stimulation in males have an effect
not really
what is adrenogenital syndrome most commonly caused by
inherited enzymatic defect in the cortisol steroidogenic pathway
how to treat cortisol deficit with ACTH increase
glucocorticoids - replaces cortisol deficit - inhibits hypothalamus and pituitary so that ACTH secretion is suppressed
ADRENOCORTICAL INSUFFICIENCY
ADRENOCORTICAL INSUFFICIENCY
what happens if one adrenal gland is non-functional or removed
the other healthy organ takes over the function of both
if one gland is affected then the patient has adrenocortical insufficiency true or false
false both glands must be affected as if one gland is non-functional then the other hypertrophies
what is another name for primary adrynocortical insufficiency
Addison disease
what is the problem in Addison disease
all layer of the adrenal cortex are under secreting
what is the common cause of Addison
autoimmune destruction of the cortex
why may secondary adrenocortical insufficiency occur
because of a pituitary or hypothalamic abnormality - results in insufficient ACTH secretion
is Addison disease fatal
yes
is aldosterone essential for life
yes
what do patients with aldosterone deficiency present with
- K+ retention (hyperkalaemia) - Na+ depletion (hyonatremia)
what does K+ retention cause
cardiac abnormality
symptoms of Addison
- poor response to stress - hypoglycaemia - lack of permissive action for metabolic activities - hyperpigmentation
why does hyperpigmentation occur in Addison
high levels of ACTH can bind with alpha-melanocyte stimulating hormone causing darkening of the skin
ADRENAL MEDULLA
ADRENAL MEDULLA
what does sympathetic pathway consist of
two neurons in sequence
what is the neurotransmitter released by the sympathetic post ganglionic fibre
norepinephrine
what receptors do norepinephrine bind to
adrenergic receptors
what does the adrenal medulla consist of
modified postganglionic sympathetic neurons called chromaffin cells
what happens when chromaffin cells stimulated
they release their chemical transmitter directly into circulation
what is the norepinephrine called that is released from the adrenal medulla
epinephrine
what class do epinephrine and norepineprhine belong to
catecholamines
what are catecholamines derived from
amino acid tyrosine
where is catecholamines synthesised
entirely within the cytosol of the adrenomedullary secretory cells
once produced where are catecholamines stored
in chromaffin granules
how are catecholamines secreted into the blood
by exocytosis of chromaffin granules
what’s most abundant epinephrine or norepinephrine
epinephrine
where is epinephrine produced
adrenal medulla
what are the 4 receptors for epinephrine and norepinephrine
- alpha 1 - alpha 2 - beta 1 - beta 2
what does norepinephrine bind predominantly with
alpha and beta 1
what does epinephrine activate
beta 2 receptors
where are beta 2 receptors
- skeletal muscles
what is the overall function of epinephrine
reinforce the sympathetic nervous system
what support peak physical exertion and stress
sympathetic nervous system and epinephrine
does epinephrine have a role in blood pressure
yes
does norepinephrine dilate the airways
nope
does epinephrine and norepinephrine stimulate bladder emptying
no they inhibit bladder emptying
epinephrine effect on blood glucose
increase it
epinephrine and insulin
inhibits insulin
epinephrine is responsible for rest and digest
no fight or flight
can the brain use fatty acids for energy
no
epinephrine increase heart rate true or false
true
epinephrine causes swathing true or false
true
epinephrine constricts the pupils true or false
false dilate pupils
what is catecholamine secretion by the adrenal medulla controlled by
sympathetic input into the gland
how much can epinephrine be increased during stress
300 times
diagram
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diagram
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diagram
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