Flashcards in The adrenal gland Deck (53)
where do the adrenal glands sit?
on top of there kidneys
what are the two parts of the adrenal gland?
what are the 3 parts of the adrenal cortex?
what does the zone glomerulosa produce?
what does the zone fasciculata and zone reticular produce?
cortisol and androgens
what cells make up the medulla and what do they produce?
chromaffin cells produce adrenaline and noradrenaline
what is the blood flow in the adrenal gland and what does this lead to?
from the outside cortex to the medulla
- chromaffin cells are exposed to high concentration of hormones produced in the cortex
what is the chromaffin cells innervated by?
sympathetic branch of autonomic nervous
what are the 3 major classes of steroid hormones?
what are the 4 principal hormones that the adrenal glands produce?
1. Cortisol (a glucocorticoid)
2. Aldosterone (a mineralocorticoid) – covered in renal
3. Adrenaline (a.k.a. epinephrine)
4. Noradrenaline (a.k.a. norepinephrine)
what other hormones are produced from adrenal glands?
what is the function of cortisol?
It acts to increase plasma [glucose] by enhancing mobilisation of AAs in many tissues and to enhance the ability of the liver to convert these AAs into glucose by activating gluconeogenesis
Once secreted , what does cortisol bind to?
-90% of cortisol is transported bound to corticosteroid-binding globulin (CBG; a.k.a. transcortin)
-~7% bound to albumin
-3-4% of circulating cortisol is free
what type of receptor does cortisol bind to?
cytoplasmic receptor that translocates to the nucleus and modulates transcription in various tissues
how does cortisol affect the liver?
Cortisol induces synthesis of enzymes involved in metabolism of AAs, facilitating conversion to glucose through gluconeogenesis
how does cortisol affect skeletal muscle?
Cortisol stimulates protein breakdown, releasing AAs to be used by the liver
how does cortisol affect adipose tissue?
Cortisol induces mobilisation of fat from sub-cutaneous stores. FAs released can be used as an alternative fuel to glucose and increase availability of glucose.
(For unknown reasons, although fat is mobilised from the extremities, some is also deposited centrally)
what secretes ACTH and what behaviour does it show?
-circadian and pulsatile behaviour
what are the causes of glucocorticoid excess?
-Seen clinically in individuals prescribed glucocorticoids
-Less commonly as a result of a tumour (primary or secondary)
what are the symptoms of glucocorticoid excess ( Cushing syndrome)
-Loss of sub-cutaneous adipose and connective tissue in the extremities
-Loss of bone mineral (osteoporosis)
what also produces these side effects?
Glucocorticoid drugs with anti-inflammatory actions also produce these side-effects
what are the symptoms of adrenal insufficiency?
-Failure of adrenal cortical hormone secretion leads to increases in circulating concentrations of ACTH
-Lack of glucocorticoid: predisposes to hypoglycemia
-Lack of aldosterone: hyperkalemia
-Combined absence: leads to hypotension
what is the most common cause of adrenal insufficiency?
autoimmune adrenal disease
what is the function of aldosterone?
[Aldosterone determines extracellular fluid (ECF) volume by regulating ECF Na+]
-Na+ is the primary osmotically active particle in ECF, therefore the amount of Na+ that is present determines the ECF volume
ECF volume is a prime determinant of arterial BP, therefore aldosterone plays an important role in the maintenance of BP
what is the primary regulator of ECF osmolarity?
what is the primary regulator of ECF volume?
how is aldosterone produced?
glomerulosa cells of the adrenal cortex synthesise aldosterone from cholesterol, through progesterone
what secretagogues enhance secretion?
(in order of influence):
-Peptide hormone ANG II
-Increase in extracellular [K+]
-(ACTH weakly promotes aldosterone secretion)
what does aldosterone bind to once its secreted?
~37% remains free in plasma. The rest weakly binds to CBG (~21%) and albumin (~42%).