Renal Hemodynamics- Weber Flashcards by Madeline Wing

kidney functions to ______ metabolic waste products, foreign chemicals, drugs, and hormone metabolites

excrete

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kidneys______ water and electrolyte balance (by increasing excretion or reabsorption)

regulate

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what happens if Na+ intake increases

kidney compensates by excreting what we have in excess

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the kidneys regulate arterial pressure by stimulating what system

RAAS

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kidneys regulate what balance by excreting HCO3- if pH goes above 7.4

acid-base balance

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what 3 things does the kidney help synthesize

erythrocytes
vitamin D (active form)
glucose

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most important function of kidneys

filtering the plasma

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what is so important about filtering the plasma

get the waste products out of blood

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kidney filters the plasma and then does what

puts the filtered plasma back into blood

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severe abnormalities of body fluid volumes and composition occur in this patient

patient with chronic kidney disease or acute kidney failure

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if you see patient with abnormal ion concentrations and body fluid volumes what are you thinking

kidney disease

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_____% of what is filtered in bowman’s capsule gets picked up by what

60-70%; peritubular capillaries

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nephrons are coupled w/ what

renal vasculature

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3 main kidney processes

glomerular filtration
tubular reabsorption
tubular secretion

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net effect of 3 main kidney processes

excretion

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what do we see in urine

what was removed from the blood

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site where tubular reabsorption mainly happens

PCT

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site where tubular secretion mainly happens

DCT and collecting duct

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baroreceptors of the kidney

JG cells

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what part of renal corpuscle allows us to maintain high pressure and create ultrafiltrate

fenestrated endothelium of capillaries

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sense solute delivery (what gets moved into glomerular capillaries)

macula densa

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___% of plasma that enters glomerulus is filtered

20%

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____% of plasma that enters glomerulus is not filtered and leaves through efferent arteriole

80%

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general cardiac output of body in liters

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___% of perfusion of whole system goes to the kidneys

20%

normal GFR

125 ml/min

why is the control of GFR so important?

b/c our entire plasma volume is filtered 60X per day

what 2 things influence how things are filtered:

1. particle size 2. charge

smaller particles like water, Na+, and glucose are freely or not freely filtered

freely filtered (1.0)

one of the key components of generating oncotic pressure

albumin (protein)

not freely filtered (good b/c want to keep this in vascular space)

albumin

presence of protein in urine sample means what

something is wrong

GBM has negative charge, so what molecule is negatively charged and kept from being filtered

albumin (protein)

if Jv is positive, what happens

fluid is moving out of capillary

if Jv is negative what happens

fluid is moved into capillary

Kf (filtration coefficient) depends on what

of opened capillaries

Pc (capillary hydrostatic pressure) depends on what

MAP and arterial resistance; MVP and venous resistance

Pif (interstitium hydrostatic pressure) depends on what

interstitial fluid volume (lymphatic fluid reabsorption)

changes with what

endothelial permeability

depends on what

plasma protein concentration

depends on what

interstitial protein concentration

GFR

Pgc= glomerular capillary hydrostatic pressure Pbs= bowman's space hydrostatic pressure

oncotic capillary pressure

bowman's space oncotic pressure

under normal conditions, no protein is filtered into urine so what should be 0

4 main things that affect GFR

1. Kf 2. hydrostatic pressure in glomerular capillaries 3. hydrostatic pressure in bowman's space 4. oncotic pressure in glomerular capillaries

what does this depend on

plasma protein concentration

if GFR is positive, fluid movement is where

out of capillary

Decrease number of functional glomerular capillaries Thickening of glomerular capillary membranes Chronic unmanaged HTN or diabetes mellitus (decrease renal function)

will affect Kf

downstream blockage such as a kidney stone or ureter blockage causes increase in upstream pressure where

hydrostatic pressure in bowman's space (Pbs)

this pressure is typically constant b/c protein stays in capillary, but can be altered during extreme starvation

oncotic pressure

what stays fairly constant between afferent and efferent arterioles

hydrostatic pressure (Pgc)

what significantly decreases from afferent to efferent arteriole

ultrafiltration rate

why does oncotic pressure increase when you move through glomerular capillaries?

concentration of protein increases

important in controlling filtration and is the primary driver in maintaining GFR

Pgc (hydrostatic pressure from glomerular capillaries)

resistance regulated where

arterioles

lower pressure at end of efferent arteriole why

because blood is going through peritubular capillaries and back into renal vein to system; so matches pressure of other capillaries

normal pressure through capillaries

25 mmHg

high mmHg seen in afferent arteriole

60 mmHg

2 main things that regulate Pgc (hydrostatic pressure of glomerular capillaries)

1. MAP 2. arteriole resistance

increase in MAP, increases blood flow into kidneys=

increase in Pgc, net filtration pressure and GFR

increase resistance of afferent arteriole=

decrease in GFR

what regulates renal blood flow

arteriole diameter

RBF =

pressure/resistance

resistance is set by balance of what

vasoconstrictors and vasodilators

activates a1 receptors (vasoconstriction)

SNS and catecholamines

vasoconstrictor and decreases RBF

Ang II

potent vasoconstrictor released in response to endothelial damage

endothelin

causes dilation of afferent arterioles and constriction of efferent arterioles (increase GFR)

ANP

vasodilation of both afferent and efferent arterioles; protective for RBF when Ang II is increased

prostaglandins

vasodilation of renal arterioles and treats hemorrhage

dopamine

maintains vasodilation of kidneys

2 main ways RBF is autoregulated

myogenic regulation tubuloglomerular feedback

describe autoregulation of RBF (myogenic regulation)

increase in arterial pressure, stretch, and then vasoconstrict

JG cells sense afferent arteriole pressure macula densa cells sense NaCl delivery renin release and RAAS as appropriate

tubuloglomerular feedback

if there is an increase in solute delivery sensed by macula densa, what does that mean for GFR

it is increased

is tubuloglomerular feedback response positive or negative feedback

negative

response to low GFR (5 things)

1. JG cells sense decrease in perfusion pressure 2. renin release 3. RAAS activated 4. increase in bp and volume 5. homeostasis restored

Of what we filter through glomerular capillaries, we absorb about _____% into peritubular capillaries

70%

Jv is always _______ in peritubular capillaries

negative (reabsorption)