Renal Hormones Flashcards
What is a hormone?
a chemical substance made in one or more locations which is carried by the blood to other areas where it has an effect on cellular function
What is an autacoid?
• Substance produced in an area that has an effect on tissue in the same area.
What is the GFR?
the total volume of fluid that is filtered from the plasma into the nephrons per unit time
What are the two intrinsic mechanisms of regulating GFR?
- Myogenic mechanism
2. Tubuloglomerular feedback machanism
What is the myogenic mechanism of GFR control?
The rise in pressure in the afferent arteriole of the glomerulus causes the arteriole to vasoconstrict and vice versa
Usually the GFR remains autoregulated (i.e. relatively constant) despite the fluctuations in arterial pressure that occur during a person’s normal activities. When can this fail?
At extremes of blood pressure, autoregulation fails and GFR and RBF vary directly with the systemic blood pressure.
What is the MOA of the tubuloglomerular feedback mechanism?
Macula densa senses increased flow (and [NaCl]) from increased filtration rate, and changes arteriole resistance through chemical mediators
What is the function of adenosine in the kidney?
decreases GFR
Decreased renin
What are the two things that the macula densa is sensing?
Flow
Na delviery
What is the chemical released by the macula densa in response to increased flow? What does this cause?
Adenosine
Lowers GFR and lower renin (to lower BP)
What is the effect of renin?
Increase BP by reabsorbing Na and causing angiotensin II formation
What is the chemical released by the macula densa in response to decreased flow? What does this cause?
NO, prostaglandins
Increases GFR and renin
How are afferent and efferent arterioles regulated relative to one another (directly or inversely)?
Inversely
Why do we want to uncouple BP and excretion regulation?
Sudden BP changes could interfere in fluid and electrolyte balance.
True or false: the proximal tubule almost always removes about 2/3 of the solutes from the tubule?
True
What is pressure diuresis?
Increased loss of fluids when BP increases
What is pressure natriuresis?
Increased loss of fluids when plasma Na increases
What are the two ways the kidneys are related to HTN? What is the consequence of this?
- Hypertension (for any reason) can cause renal damage and increased nephron flow
- Any form of renal damage tends to cause hypertension
=bad feedback
What is the effect of PGE2 and PGI production when angiotensin II/norepi/vasopressin is released? What is the effect on the kidney?
Increases,
thus can oppose vasoconstrictors produced by the macula densa
What is the mechanism through which chronic aspirin or IBU use can lead to renal damage?
If you reduce the amount of PGE2 and PGI2 synthesized unopposed vasoconstriction might cause renal damage
What happens to a pt with kidney damage when they take NSAIDs?
Inhibit vasodilation (which would be up in a damaged kidney), leads to ischemic nephrons
Which part of a kidney is particularly susceptible to ischemia? What is the consequence of this?
medullary blood flow
If there is damage, one sign may be the inability to produce concentrated urine (since this is where juxtaglomerular nephrons are)
What is the effect of norepi and epi on the adrenal medulla?
Constrict both the afferent and efferent arterioles thus decreasing renal blood flow and GFR.
More alpha 1 on afferent arterioles
What is the effect of angiotensin II generally? On the kidneys?
Vasoconstrictor in the systemic circulation
preferentially constricts the efferent arteriole under most physiological conditions
