Lecture: Adrenal gland Flashcards
The Major Endocrine Organs
pineal gland
hypothalamus
thyroid gland
adrenal gland
pancreas
ovaries testes
parathyroid gland
Adrenal gland activated in response to
stress
Bodily symptom-
Catecholamines
e.g. adrenaline
Metabolic effects- Glucocorticoids
e.g. cortisol
sodium effects- Mineralocorticoids
e.g. aldosterone
Adrenal gland
Hormones of the adrenal medulla - catecholamines
-Regulation of secretion
-Actions
Hormones of the adrenal cortex - mineralocorticoids
-Actions of aldosterone
-Regulation by renin-angiotensin system
Hormones of the adrenal cortex - glucocorticoids
-Regulation of cortisol secretion
-Role of the H-P-A
-Actions
Hormones of the Adrenal Medulla
tyrosine-DOPA- Dopamine- noradrenaline- adrenaline
Regulation of Secretion
The adrenal medulla is a part of the sympathetic division of the autonomic nervous system.
Can be considered as a specialised group of postganglionic neurons (- axons).
Secretion is controlled by sympathetic preganglionic nerve fibres.
Effects of medullary catecholamines
Virtually the same as direct activation of sympathetic nerves except
last much longer (minutes)
effects generalized to all cells with alpha and/or beta-receptors (GPCRs)
Major physiological effect is on cardiac output and cellular metabolism due to greater effect of AD than NA at -receptors
Actions of Adrenal Catecholamines
hypothalamus stimulated by stress, physical activity and low blood glucose levels
action potentials through the sympathetic division of the autonomic nervous system
adrenal medulla
epinephrine and norepinephrine
increased release of glucose from liver
increased release of fatty acids from fat stores
increase in heart rate
increase constriction of visceral blood vessel
increased blood pressure
Adreno-cortical hormones
mineralocorticoids to aldosterone
glucocorticoids to cortisol, corticosterone
Actions of aldosterone- mineralocorticoids
Stimulates the reabsorption of Na+ /excretion of K+ in the cortical collecting ducts
Decreases the ratio of [Na+] to [K+] in sweat and saliva
Increases the reabsorption of Na+ in the colon and excretion of K+ in the faeces
Overall effect of aldosterone is to retain Na+ in the body at the expense of K+
Net effect is an increase plasma volume and hence cardiovascular pressure
regulates The Renin-Angiotensin System
Drugs that affect aldosterone actions
ATII antagonist: LOSARTAN
Similar to ACE inhibitors,
used in hypertension
ACE inhibitors: CAPTOPRIL, ENALAPRIL
Anti-hypertensive
Cardiac failure
Aldosterone antagonist: SPIRONOLACTONE
Potassium-sparing diuretic
Hyperaldosteronism (Conn’s disease)
Adrenal glucocorticoids
Regulation of Glucocorticoid Secretion
stress or nonstress neutral inputs
hypothalamus- secretes CRH(Corticotrophin Releasing Hormone)
increase in plasma CRH
anterior pituitary
increase in ACTH (Adreno Cortico Trophic Hormone)
secretion
increase plasma ACTH
Adrenal cortex
increase in cortisol secretion
increase plasma cortisol
targets cells for cortisol
Circadian rhythm in cortisol secretion
The fluctuations in cortisol secretion are caused by fluctuations in ACTH secretion from the pituitary gland.
Corticosteroids
Cause rise in plasma glucose levels (release from liver and increased gluconeogenesis)
This causes increase in proteolysis, which in turn
can bring about muscle wasting, skin thinning
Cause fat redistribution (as in Cushing syndrome)
moon face, buffalo hump
Cause increased breakdown of triglycerides,
leading to a rise in plasma fatty acid levels
Suppress inflammation and immune responses
Cushing’s disease - cortisol excess
Salt balance
increased sodium
reduced potassium
(mineralocorticoid xs
CNS
depression
euphoria
Cardiovascular
hypertension
increased blood volume
leukocytosis
erythrocytosis
Cellular metabolism
hyperglycaemaia
fat redistribution
truncal obesity
weak muscles, skin and bone
poor wound healing
Inflammatory and immune system
decreased inflammatory response
increased susceptibility to infection
decreased fibrous tissue formation
Addison’s disease - cortisol deficiency
Salt balance
reduced sodium
increased potassium
(mineralocorticoid loss)
CNS
Fatigue
anorexia
Inflammatory and immune system
tendency towards autoimmune disease
Cardiovascular
vasodilation
hypotension
reduced blood volume
anaemia
lymphocytosis
Cellular metabolism
hypoglycaemaia
weight loss
