Ganong 24th ed - Chapter 20 - Adrenals (1) Flashcards
Name the major steroid hormones that are produced in the adrenal cortex.
Aldosterone, Cortisol, Androgens
Name the layers of the adrenal cortex, in order from outer to inner.
Mnemonic GFR: capsule –> Glomerulosa –> Fasciculata –> Reticularis –> medulla
Explain which layer of the adrenal cortex produces each hormone.
Mnemonic ACTH: from outer to inner layers: Aldosterone (glomerulosa) –> Cortisol (fasciculata) –> Testosterone Hormones (reticularis)
Name the hormones that are synthesized in the adrenal medulla.
Adrenaline, Noradrenaline, Dopamine.
What is the precursor molecule in the synthesis of catecholamines?
The amino acid tyrosine is the precursor to the synthesis of dopamine, noradrenaline and adrenaline.
What happens to plasma noradrenaline levels and adrenaline levels after adrenalectomy?
The noradrenaline levels remain the same, but the adrenaline levels fall essentially to zero. Some time after the adrenalectomy, there may be some production of adrenaline by extra-adrenal tissues.
Why is the adrenal medulla considered to be like a ganglion?
Because it is innervated by preganglionic sympathetic nerve fibres that release acetylcholine, triggering adrenal medullary cells to undergo exocytosis of their granules of catecholamines, just as a post-ganglionic nerve fibre would do.
Explain the effects of both adrenaline and noradrenaline on peripheral blood vessels.
Noradrenaline produces vasoconstriction via alpha-1 receptors in most organs. The net effect of a noradrenaline infusion is an increase in TPR.
Noradrenaline has little effect on beta-2 receptors.
Adrenaline produces vasodilation via beta-2 receptors in skeletal muscle and liver. This usually overrides the vasoconstriction that it produces in other tissues via alpha-1 receptors, and the net effect is a decrease in TPR.
What are the effects of adrenaline and noradrenaline infusions, into a HEALTHY patient, on each of the following:
- TPR
- Cardiac Output
- MAP
- Pulse Pressure
- HR
- TPR: Adrenaline decreases, NA increases
- CO: Adrenaline increases, NA decreases
- MAP: Adrenaline same-ish, NA increases
- PP: Adrenaline widens, NA same-ish
- HR: Adrenaline increases, NA decreases
Why does a noradrenaline infusion into a HEALTHY person produce a lowered heart rate and lowered cardiac output?
Because of the baroreceptor reflex. NA increases the MAP, and so there is a reflex bradycardia.
Adrenaline and NA stimulate insulin and glucagon secretion via (alpha or beta) adrenergic mechanisms. They inhibit insulin and glucagon secretion via (alpha or beta) adrenergic mechanisms.
Stimulate via beta-adrenergic receptors.
Inhibit via alpha-adrenergic receptors.
The hormones of the adrenal cortex are all derivatives of which molecule?
Cholesterol.
What is a major physiological effect of glucocorticoids, with regard to metabolism in normal subjects?
Glucocorticoids stimulate the metabolism of proteins, carbohydrates and fats. (causing protein catabolism, increased glycogen synthetase and decreased peripheral use of glucose)
What effect do glucocorticoids have on the circulating numbers of each of the following:
- Platelets
- Lymphocytes
- Eosinophils
- Basophils
- RBCs
- Neutrophils
Lowered numbers of: - Eosinophils - Basophils - Lymphocytes Increased numbers of: - Platelets - RBCs - Neutrophils
What causes Cushing Syndrome?
An excess of glucocorticoids. This can be caused by a pituitary tumour (causing excess ACTH), or an adrenal tumour (causing excess production of glucocorticoids), or prolonged administration of exogenous glucocorticoids.
