Ganong 24e chapter 38 - Regulation of ECF (1) Flashcards
RAAS - Which cells secrete renin?
The juxtaglomerular cells of the renal afferent arterioles.
RAAS - What does renin do?
It acts on angiotensinogen in the liver, to convert it to angiotensin-I, which is then converted to angiotensin-II in the lungs by ACE.
RAAS - What does angiotensin-II do?
Angiotensin-II promotes the release of aldosterone from the adrenals, and also stimulates the production of more aldosterone. Angiotensin-II also causes systemic arteriolar vasoconstriction and a rise in BP.
RAAS - What does aldosterone do?
Aldosterone acts on the DCT and collecting ducts to increase the number of Na+ channels, thereby increasing sodium reabsorption (and water follows by osmosis). It also increases Na/K/ATPase activity, thereby pumping more K+ out, thereby increasing K+ excretion.
RAAS - What stimulates the RAAS to become activated?
A drop in BP / Fall in extracellular sodium levels / Reduced extracellular fluid volume / Dehydration
Where is vasopressin released from, and which structures regulate is secretion?
It is stored in the posterior pituitary, and released from there into the bloodstream. Its release is regulated by osmoreceptors in the hypothalamus.
What is the normal osmolality of plasma?
285mOsm/kg (remember that osmolality is per kg, and osmolarity is per L)
What is the main dysfunction in diabetes insipidus?
There is a deficiency of vasopressin, or there is a poor response to vasopressin. This causes polyuria and polydipsia.
What are ANP and BNP, and where do they come from?
These are both natriuretic peptide hormones. ANP comes from the atria, and BNP comes from the whole heart including the ventricles.
What stimulates release of natriuretic peptide hormones?
Stretch on the atria and ventricles.
Where is erythropoietin produced? What is its basic structure?
85% in the kidneys, 15% in the liver. Glycoprotein.
What is the most important determinant of ECF volume?
The amount of Na+ in the ECF.
