Adrenal Physiology Flashcards
What are the layers that make up the cortex of the adrenal gland
Outer capsule
Zona glomerulosa
Zona fasciculata
Zona reticularis
Overview of corticosteroids
They are lipid soluble
Bind to intracellular receptors
Alter gene transcription directly or indirectly
Action depends on structure
What corticosteroid is synthesised in the Zona glomerulosa
Mineralocorticoids such as aldosterone
What corticosteroid is synthesised in the Zona fasciculata
Glucorticoids such as cortisol
What corticosteroid is synthesised in the Zona reticularis
Androgens such as DHEA and androstenedione
What is the function of the hormones synthesised in the Zona glomerulosa
They are important for regulating fluid balance
What percentage of the cortex does the Zona glomerulosa account for
15%
What type of hormones are mineralocorticords
Steroid hormones
What is the function of aldosterone
Responsible for controlling the uptake of Na+ and secretion of K+ in the collecting duct of the Renal tubule
What factors increase the rate of aldosterone production in the Zona glomerulosa
Increased plasma concentration of angiotensin-II
Increase in plasma K+ concentration
Decrease in plasma pH
Decrease in blood pressure
What causes Conn’s syndrome
It is caused by an Adenoma/benign tumour in the Zona glomerulosa which causes excess secretion of aldosterone
Which is the thickest layer of the adrenal cortex
The Zona fasciculata
What percentage of the cortex does the Zona fasciculata make up
50%
What type of cell is the Zona fasciculata made up of
Parenchymal cells known as spongiocytes
What is the function of hormones made in the Zona fasciculata
They regulate carbohydrate metabolism particularly when an individual is in a time of stress
What causes Cushing’s syndrome
A patient with Cushing’s syndrome will have symptoms of high gluticocorticoid secretion and show effects of high mineralcorticoid concentrations
What can cause Addison’s disease
Lack of cortisol due to an autoimmune destruction of the adrenal cortex
What is the function of the androgens secreted from the Zona reticularis
They are largely responsible for the Normal development of sexual characteristics during puberty
How are adrenal androgens regulated
Adrenal androgens are regulated by ACTH which is secreted from the anterior pituitary stimulated by the release of CRH into the hypophyseal portal system by the hypothalamus
What is the adrenal medulla
It is the central part of the adrenal gland and is surrounded by it the cortex
What is the role of the adrenal medulla
Plays a very important role in homeostasis, secreting essential hormones such as adrenaline and noradrenaline
What are the main secreting cells of the medulla
Chromaffin cells (modified sympathetic ganglia) derivatives of neural crest cells
When is adrenaline released from the medulla
In response to the activation of the sympathetic nervous system
What is the main function of the adrenal medulla
Primary function = Synthesising catecholamines such ad adrenaline and noradrenaline
Secondary function = production of dopamine
