lecture 4 Flashcards
Adrenal cortex features
Stimulates by stress response
Produces steroid hormones derived from steroids (corticosteroids)
Regulation of Na+ and K+ and fluid volume
Zones of the cortex
Glomerulosa = aldosterone
Fasciculata = cortisol ( and androgens)
R = androgens
medulla
Medulla hormones
Adrenaline and noradrenaline
Cortisol
Stress hormone
Secreted from zone fasciculate
Release controlled by CRH/ACTH
Circadian rhythms and CRH
CRH secretion synchronised with sleep/wake cycle
Stress induced secretion of CRH increases glucocorticoid/cortisol secretion and overrides rhythms
Actions of cortisol/glucocorticoid
provides fuel
protects CVS
depresses inflammation and immune responses
Metabolism - how is it regulated using cortisol .. LOW BLOOD GLUCOSE
Insulin decreases Glucagon increases Growth hormone increases Cortisol increases Hunger increases release of fats from white fat
Cortisol effect on CVS
Increases contractility and force of contraction
Increases peripheral resistance
Increases effects of noradrenaline and adrenaline
Increases number of angiotensin receptors
Hypertension and cortisol
Common In Cushings
Excess cortisol
Hypotension and cortisol
Common in Addisons
Deficit of cortisol
Cortisol - inflammatory and immune response
Antiiflammaory and immunosuppressive
Inhibits secretion of cytokines, histamine release, proliferation of immune cells and synthesis of antibodies
Therapeutic use of glucocorticoids ( cortisol )
reduce inflammation
damp down immune responses
How is cortisol regulated
Hypothalamus releases CRH via portal hypophyseal circulation
Anterior pituitary releases ACTH via systemic circulation
Adrenal cortex ( cortisol)
Feedback control of cortisol
Time of day ( shift work) - circadian rhythm
Negative feedback
Positive feedback - physical and emotional
AVP =
ADH
Aldosterone main function
main role is to regulate salt and water in the body, thus having an effect on blood pressure.
Aldosteorne is secreted from
Adrenal gland - glomerulosa zona
How is aldosterone released
Low Na stimulates renin release in kidney
Renin cleaves angiotensinogen to Ang I
Ang I converted to Ang II
Aldosterone stimulates..
Na-K ATPase in collecting ducts
Na reabsorbed from filtrate
K secreted into filtrate
Water retention
Corticosteroid receptors
Steroids fat soluble
Cytosolic receptors
- Glucocorticoid receptors - CORTISOL
- Mineralocorticoid receptors - ALDOSTERONE
paths to disregulation fo cortisol
Primary = adrenal cortex - cortisol/aldosterone Secondary = Anterior pituitary( ACTH) Tertiary = hypothalamus ( CRH)
Too little cortisol - primary deficit
Failure of adrenal cortex to secrete cortisol
Loss of negative feedback on CRH and ACTH secretion
CRH and ACTH increase
Too little cortisol - secondary deficit
Failure of pituitary to secrete ACTH
Loss of negative feedback
CRH high but ACTH low
Atrophy of adrenal cortex
Symptoms of Addisons ( too little cortisol )
Hypotension Hypoglycemia Hyponatremia Hypovolumia Hyperpigamnetation Hyperkalaemia
Hyperkaeamia
High K+ Suggests lack of aldosterone
Main causes of Addisons
Autoimmune destruction of adrenal cortical cells = primary
Chronic glucocorticoid treatment = secondary
Infection
Drugs that inhibit cytochrome p450
Cortisol resistance
Treatment ( urgent ) for addisonian crisis
High dose IV
Fludrocortisone - mineralocorticoid ( primary)
Glucocorticoid and fluids
Need to restore blood volume, pressure and sugar
Cushings disease symptoms
Muscle wasting
High blood sugar
Fat deposition
Hypertension
Cushings disease
ACTH high
Stimulastes MR
Raises blood volume,blood pressure and Na
Excess cortisol effects
Reduces inflammation - asthma, IBS,
Supresses immune system - MS
Atrophy of zone fascicula ( cortex)
Cushings treatment
Remove or destroy abdnormal source of ACTH/cortisol
Why shouldn’t steroids be stopped suddenly
treatment will reduce ACTH secretion via negative feedback
Low ACTH = atrophy of cortex
Tapering off= ACTH can rise, growth of cortex is stimulated
What is aldosterone release controlled by
Ang II
Addisons crisis
Circulatory collapse Hypoglycaemia Nausea and vomiting Weakness Depression and fatigue
