The Adrenal Gland Flashcards
What is the adrenal medulla?
A modified sympathetic ganglion derived from neural crest tissue
What does the adrenal medulla secrete?
Catecholamines - epinephrine, noradrenaline, dopamine
What is the adrenal cortex?
A true endocrine gland from the mesoderm
What does the adrenal cortex secrete?
- Mineralocorticoids
- Glucocorticoids
- Sex Steroids
What are the two main products of the adrenal cortex?
Cortisol and Aldesterone
What is DHEA?
A pre-hormone of testosterone and oestrogen
What do defects in 21-hydroxylase cause?
congenital adrenal hyperplasia (aldosterone and cortisol and is associated with a disruption of salt and glucose balance)
Ambiguous genitalia
Why does a deficit in 21-hydroxylase cause adrenal hyperplasia?
- Lack of 21-hydroxylase inhibits synthesis of cortisol
- This removes the negative feedback ACTH and CRH release
- Increased ACTH secretion is responsible for enlargement of adrenal glands
- Negative feedback of ACTH on CRH synthesis remains
What is cortisol ?
A glucocorticoid hormone which influences glucose metabolism
What is cortisol bound to?
CBG
When is cortisol released?
Burst at 6-9am
Lowest level - midnight
What are cortisol levels linked to?
Stress
What occurs if the adrenal glands are removed?
Animals cannot deal with stress as it cannot deal with hypoglycaemia = no maintenance of ECF
How does cortisol affect gluconeogenesis?
Cortisol stimulates formation of gluconeogenic enzymes in the liver, thus enhancing gluconeogenesis and glucose production.
How does cortisol affect proteolysis?
Cortisol stimulates the breakdown of muscle protein to provide gluconeogenic substrates for liver
How does cortisol affect lipolysis?
Cortisol stimulates lipolysis in adipose tissue which increases plasma [FFA] creating an alternative fuel supply that allows [BG] to be protected whilst also creating a substrate for glucoeogenesis
What affect does cortisol have on calcium balance?
Decrease absorption from gut, increases excretion at kidney resulting in net Ca2+ loss. Also increases bone resorption
How does cortisol affect mood and cognition?
Too much causes depression and impaired cognitive function
How does cortisol affect norepinephrine?
Has a permissive effect. Too much causes cushings, too little causes hypotension
How does cortisol affect the immune system?
Reduces lymphocyte count, reduces antibody formation, inhibits inflammatory response
What is aldosterone?
A mineralcortocoid which acts on the distal tubule of the kidney to determine the levels of minerals reabsorbed/excreted
What pathway controls aldosterone secretion?
Renin-Angiotensin-Aldosterone System (RAAS)
What occurs when aldosterone levels are increased?
Na+ is released, H2O is retained, K+ is depleted and blood volume & blood pressure is increased
What occurs when aldosterone levels are decreased?
Leads to Na+ and H2O loss, increased K+ within plasma, diminised blood volume and blood pressure
What occurs in hypersecretion of cortisol?
Cushings disease
What occurs in hyposecretion of cortisol?
Addisons
When is CRH and ACRH release promoted?
During periods of stress
