Renal VIII: Hormonal Regulation of Body Salts Flashcards
The kidneys are responsible for maintaining a normal body _______ to keep ______ constant.
NA+ content; ECF volume
What does the effective circulating volume (ECV) reflect?
It reflects the portion of ECF volume within the vascular system that is effectively perfusing the tissues.
What are the main efferent effectors regulating the effective circulating volume?
- renal sympathetic nerves
- renin-angiotensin-aldosterone system (RAAS)
- atrial natriuretic peptide (ANP)
What are the afferent vs. efferent regulators of sodium excretion?
Afferent:
- volume receptors (cardiac atria, intrathoracic veins)
- pressure receptors (baroreceptors, afferent arteriole)
- tubular fluid [NaCl] (macula densa)
Efferent:
- neurohormonal (RAAS, SNS, ANP)
- hemodynamic (GFR)
Explain the concept of tubuloglomerular feedback.
It involves the macula densa sensing flow and salt content in the lumen. If tubular flow and Na+ content are high, there is contraction of the afferent arteriole. If tubular flow and Na+ content are low, prostaglandins and NO are released.
Where is renin produced/secreted?
It is produced by granular juxtaglomerular cells on the afferent arteriole just before the glomerulus.
What stimulates release of renin from granular JG cells?
- sympathetic nerve activation
- macula densa (releases prostaglandins to cause increased renin secretion)
- decreased afferent arteriole pressure (sensed by intrarenal baroreceptors)
ANP is synthesized and released from cardiac atria under which conditions, and what is its effect?
high pressure or stretch; its effect is to increase salt wasting (natriuresis) in order to decrease blood pressure/volume - it does this by constricting efferent arterioles, thereby increasing GFR and decreasing Na+ reabsorption in the collecting ducts
What is a common treatment for edema?
diuretics (easy way to decrease capillary hydrostatic pressure)
How does dopamine regulate salt reabsorption?
An increase in ECV will increase dopaminergic activity, causing decreased reabsorption of Na+ and Cl- in proximal tubule
What is the major cation of the ECF compartment?
Na+!
What is positive vs. negative sodium balance?
- positive: Na+ intake > Na+ excretion
- negative: Na+ intake < Na+ excretion
What does slow tubular flow stimulate?
the JGA, which causes secretion of renin to increase blood volume and pressure
TG feedback causes what to be released when the macula densa senses low flow and low salt? Why?
prostaglandins and NO; both are powerful vasodilators
Catecholamines (sympathetic stimulation) act on ______ receptors of ________ cells.
beta-1; juxtaglomerular
