Flashcards in Renal Hormones Deck (94):
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?
1. 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?
What are the two things that the macula densa is sensing?
What is the chemical released by the macula densa in response to increased flow? What does this cause?
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?
Increases GFR and renin
How are afferent and efferent arterioles regulated relative to one another (directly or 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?
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?
1. Hypertension (for any reason) can cause renal damage and increased nephron flow
2. Any form of renal damage tends to cause hypertension
What is the effect of PGE2 and PGI production when angiotensin II/norepi/vasopressin is released? What is the effect on the kidney?
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
Angiotensin II preferentially constricts the efferent arteriole under most physiological conditions How is the afferent arteriole protected from this?
Vasodilator release by macula densa
What is the effect of unopposed angiotensin II? How?
Increased GFR b/c efferent arterioles constricted while afferent not
What is the relationship of efferent arteriole resistance relative to GFR and renal blood flow?
Direct with GFR
Inversely with renal blood flow
What is the relationship of afferent arteriole resistance relative to GFR and renal blood flow?
Inverse with both GFR and renal blood flow
What is glomerular tubular balance?
1. Renal tubules increase their reabsorption rate when GFR increases
If the number of nephrons is decreased, the kidneys compensate how? How is this effected?
by increasing the filtration of each nephron
increasing PGE2 and PGI2 thus dilating afferent arterioles and increasing single nephron GFR.
What are the effects of Epi and norepi on the kidneys?
Constricts both the afferent and efferent arterioles thus decreasing renal blood flow and GFR
What is the effect of angiotensin II on the kidneys? (3)
preferentially constricts the efferent arteriole under most physiological conditions
Increase Na reuptake from tubules
Increases Aldosterone synthesis
What does the kidney do in response to low BP?
What is the function of renin?
Breaks angiotensinogen from liver into angiotensin I.
What converts angiotensin I to II?
What is the function of juxtaglomerular cells?
Release renin in response to BP changes in the kidney
What is the effect of aldosterone synthesis?
Increases renal reabsorption of sodium which can also raise blood pressure
What are the steps that the kidney takes in reposne to BP changes? (3)
1. Changes renin from juxtaglomerular cells
2. Renin converts Angiotensinogen to angiotensin I
3. Angiotensin II increases aldosterone
What are the two things that cause thirst?
1. Angiotensin II
2. Increased blood osmolality
Increased blood osmolality or decreased blood volume causes what?
increased release of ADH
What is ADH's effect on BP? How?
Increases via vasoconstriction
What are the two natriuretic peptides in the heart?
What is the signal for more ADH to be released?
Increased stretch on the right atrium
What is the effect ANP has on ADH, Renin?
What are the effects of ANP/BNP on the GFR?
Relaxes Arteriole to increase GFR
What are the effects of ANP/BNP on angiotensin II?
What are the effects of ANP/BNP on the Na/water reabsorption on the medullary collecting duct?
What are the effects of ANP/BNP on aldosterone?
What is the overall effect of ANP/BNP?
Where is erythropoietin mainly produced?
What is the function of erythropoietin?
Goes to bone marrow to stimulate RBC production
What is the enzyme that creates calcitriol from 25-hydroxycholecalciferol?
Where does the conversion of vit D3 take place?
What is the prohormone of vit D that we take in via our diet? What is the first step to convert it to previt D?
Exposure to sunlight
After previt D is converted to Vit D3 via sunlight, what happens?
25-hydroxylase converts it to 25 hydroxycholecalciferol
What is the step after formation of 25 hydroxycholecalciferol?
1alpha hydroxylase converts it to calcitriol
What is the active form of Vit D?
What are the effects of calcitriol? (3)
Stimulates renal tubule reabsorption of Ca and PO3
Suppresses PTH synthesis in the parathyroid
Stimulates FGF3 in bone
The final hydroxylation step of vit D is stimulated by what?
What is the effect of PTH?
controls plasma calcium concentration
What controls [PTH]? What is the relationship?
What are the chemical reaction in the body that take place in response to lower [Ca]?
Increase PTH, Increasing Vit D activation, increasing Ca reabsorption/release from bones
What is the relationship between PO3 and PTH?
Why is it important that PO3 an Ca vary inversely?
CaPO3 could precipitate out and cause renal stones
What is the effect of PTH on PO3 reabsorption in the kidneys and intestines?
Decreases PTH reabsorption in the kidneys
Increases in intestines
Where is the Ca drawn from bone via PTH?
The labile bone part
What are the three rapid responses to PTH synthesis?
Decreased renal PO3 reabsorption
Increased renal Ca reab
Increase bone Ca withdrawl
What are the two slow responses to PTH?
Increased osteoclast action
Increased intestinal Ca reabsorption
What is fibroblast growth factor 23 (FGF23)? (what makes it, what does it do )?
a peptide hormone that is made by osteoblasts and osteocytes in bone
Decreases PO3 reabsorption in the kidney, and decreases production of calcitriol
What stimulates FGF23 release?
Increased PO3 levels,
What is the effect of PTH on calcitriol synthesis? FGF23?
Increased by PTH
Decreased by FGF23
What is the effect of PTH on phosphate excretion? FGF23?
Both increase excretion
What is the effect of CKD on [PO3]? What is the consequence of this?
Lowers GFR, increasing [PO3]. This increases PTH, increasing bone reabsorption. =osteodystrophy
What is the effect of PTH on the kidney? Intestines?
Kidney = Increases Ca reabsorption, decreases PO3
Intestines = Increases Ca reabsorption, increases PO3
What cells synthesize FGF23?
What inhibits PTH?
What is the feedback mechanism for Vit D synthesis?
Increased Ca inhibits PTH. PTH no longer activates 1alpha hydroxylase
1alpha-hydroxylase is found where?
25alpha hydroxylase is found where?
What are the two hormones that ANP inhibits?
Where is angiotensinogen produced?
What type of sympathetic adrenoceptors are found on the kidney? What do they do?
B1, stimulate renin release
Where are osmoreceptors found/what do they synapse to?
In the hypothalamus, synapsing on the paraventricular and supraoptic nerves
How can tubuloglomerular feedback help prevent excessive fluid losses if there is damage to kidney proximal tubules?
Can redirect blood to other, "good" nephrons
What is the effect of angiotensin II on vascular smooth muscle?
What is the effect of angiotensin II on the adrenal cortex?
Stimulates aldosterone release
What is the effect of angiotensin II on the afferent and efferent arterioles?
What is the effect of angiotensin II on the thirst center?
What is the effect of angiotensin II on ADH release?
What is the effect of angiotensin II on sympathetic tone?
What are the two organs that make erythropoietin?
Liver and kidney
What is the major stimulus for erythropoietin secretion?
Hypoxia to kidneys
What is more important, the effect of vit D on the intestines or the kidneys?