Purpose of CVMP activation of the sympathetic drive
Transfer volume to central circulation
Cardiac inotropy, chronotropy
Purpose of CVMP activation of sympathetic and endocrine outflow to the kidney
Preserve GFR
Produce concentrated, Na+-free urine
Pathway by which sympathetic outflow to kidney causes increased GFR
Sympathetic stimulation of JGA → renin secretion → AI → AII → constriction of afferent/efferent arterioles → secretion of PGI → dilation of afferent arteriole → increase GFR
Densensitivity of the baroreceptor to increased pressure, over time
2 places volume can be shunted, where it is undetectable by baroreceptors
Splanchnic vessels
Arterial-venous fistulae
2 circumstances in which splanchnic shunting could occur
Cirrhosis
Sepsis
Effective perfusion = [?] x [?]
(cardiac output) x (systemic vascular resistance)
In cirrhosis, hepatic venous outflow obstruction + A-V fistulae → activation of the [?] reflex for salt retention
hepato-renal
Increased portal venous pressure (in cirrhosis) causes [?]-[?] venous shunting, resulting in [signs]
porto-systemic; hemorrhoids, varices
In cirrhosis, what pathologic liver changes cause increased portal pressure?
Distortion/fibrosis of the sinusoids
Decreased clearance of vasoconstrictors/dilators
T/F: Ascites is a sign of cirrhosis
True
The cirrhotic liver is [underperfused or overperfused]
underperfused
How does an underperfused, cirrhotic liver ultimately result in increased Na/water retention?
Distressed liver sends signal to kidney → kidney retains salt and water (hepato-renal reflex)
Example of an “overriding” stimulus leading to failure to inactivate CVMP
T/F: Arterial-venous fistulae form in cirrhosis
True
Describe the normal pathogenesis of nephrotic syndrome, leading to edema
Loss of albumin → fluid seeps out of capillaries → decreased IVF → CVMP activation → Na/water retention
How can nephrotic syndrome result in edema when albumin is not very low?
IVF overfill → secretion of ANP; but patients have acquired ANP resistance and the kidneys cannot respond to ANP
In patients with acquired ANP resistance + nephrotic syndrome, the edema subsides [before or after] the proteinuria, if the patient regains ANP sensitivity
before
Define pre-renal azotemia
Rise in BUN despite good renal function
BUN: Stands for… Is an indication of…
Blood urea nitrogen
Ability to clear nitrogenous waste
T/F: An increase in BUN always correlates with decreased glomerular filtration
False – GFR can be normal; the nephron is simply reabsorbing more urea into the bloodstream
What hormone controls urea reabsorption in the nephon?
ADH
Effect of increased BUN on: Urine volume Urine Na+ content Urine osmolarity Acid/base balance Urine K+ content
Decreased
Decreased
Increased
Metabolic alkalosis
Decreased
You should look for the symptoms of pre-renal azotemia in patients with…
Severe heart failure
What hormones cause hypokalemia and metabolic alkalosis in pre-renal azotemia?
Aldosterone, AII
What hormone causes hyponatremia and azotemia in pre-renal azotemia?
ADH
CVMP activation results in the release of…
Aldosterone and catecholamines
How does aldosterone induce metabolic alkalosis?
Increases ammoniagenesis (increase in H+ secretion and HCO3- production)
How do aldosterone and ADH cause an increase in the medullary osmotic gradient?
Aldosterone → increased Na+ reabsorption into interstitium
ADH → increased urea reabsorption into interstitium
What transporters are upregulated by aldosterone in the cortical collecting duct?
Apical ENaC and ROMK1, basolateral Na/K ATPase
In the collecting duct, why does an increase in Na+ reabsorption contribute to hypokalemia and alkalosis?
Increases the transcellular electrical gradient favoring K+ and H+ secretion into the tubule lumen
Cardio-renal syndrome results from acutely worsening [?]