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Hum Physiology II > renal blood flow, Lect 2 > Flashcards

renal blood flow, Lect 2 Flashcards

1
Q

kidneys receive what percentage of the CO

A
  • 25%, needed to support filtration
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2
Q

how much filtrate is formed per day

A

180 L

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3
Q

equation of filtration fraction

A

FF=GFR/RPF

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4
Q

equation for renal plasma flow

A

RPF = (1-Hct)RBF

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5
Q

sympathetic nerves cause vasoconstriction via what receptors? What effect does this have on RBF and GFR

A
  • alpha 1 receptors
  • decrease RBF and GFR
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6
Q

name the factors that cause vasoconstriction and decrease RBF and GFR

A
  • sympathetic innervation of alpha 1 receptors
  • angiotensin II (effects on GFR are variable)
  • ADH
  • ATP
  • endothelin
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7
Q

effect on angiotensin II on afferent and efferent arterioles

A

angiotensin II constricts both afferent and efferent arterioles however the efferent arteriole is more sensitive

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8
Q

list the compounds that vasodilate and increase RBF and GFR

A
  • atrial natriuretic peptide
  • glucocorticoids
  • NO
  • prostaglandins (PGE2, PGI2)
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9
Q

autoregulation of RBF and GFR

A

constant blood flow and GFR at different arterial pressures

  • range arterial pressures: 80-180 mmHg
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10
Q

autoregulation of RBF and GFR can be overridden by

A

large increases in sympathetic tone

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11
Q

two mechanisms which cause autoregulation of RBF and GFR

A
  • myogenic mechanism
  • tubuloglomerular feedback (“flow-dependent”)
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12
Q

myogenic mechanism

A
  • intrinsic to vascular smooth muscle cells; contract in response to stretch
  • affects RBF and GFR mainly by changing resistance of afferent arteriole
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13
Q

Tubuloglomerular feedback

A
  • increasing GFR increases NaCl delivery to LOH; sensed by the macula densa which causes the resistance of the afferent arteriole to increase thereby decreasing RBF and GFR
  • function: maintains constancy of salt load delivered to distal tubule
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14
Q

signal used in tubuloglomerular feedback

A

adenosine

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15
Q

describe the fluid in bowman’s capsule

A
  • a protein-free filtrate of blood plasma
    • all small-MW solutes that are not protein-bound appear in filtrate in the same concentrations as in blood plasma
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16
Q

list the route of filtrate from capillary lumen into urinary space

A
  1. fenestrae
  2. basal lamina
  3. filtration slits (between pedicels of podocytes)
17
Q

substances to be filtered are seperated by what characteristics

A
  • size (MW)
  • electrical charge
    • basal lamina and slits coated with negative charges
    • proteins usually have (-) charge and are repelled
18
Q

what are the main barriers to protein being filtered

A
  • basal lamina
  • filtration slits
19
Q

describe GFR using the starling equation

A
  • GFR = Kf[(PGC - PBC) - (πGC - πBC)]
    • πBC: oncotic pressure in bowman’s capsule is approximately zero bc no proteins in BC
    • Kf= filtration coefficient
    • [(PGC - PBC) - (πGC - πBC)] = net filtration pressure
20
Q

Kf

A

filtration rate produced by each mmHg of net filtration pressure

21
Q

compare Kf for glomerular capillaries vs capillaries in skin and muscle

A

Kf for glomerular capillaries is 50-100 greater than that for capillaries in skin and muscle

22
Q

Kf can be altered by what type of cells

A

mesangial cells

  • relaxation of glomerular mesangial cells increase glomerular surface area and results in an increase in GFR
  • Angtiotensin II reduces Kf
23
Q

equation calculating GFR using Kf

A

GFR = Kf x NFP

  • net filtration pressure
  • GFR = Kf (PGC - PBC - πGC)
24
Q

what is PGC

A

blood pressure in glomerular capillary

  • driving force for GFR
25
Q

PBC

A

back pressure in bowman’s capsule

  • diminishes GFR
26
Q

πGC

A

oncotic pressure of glomerular capillary blood

  • due to proteins unable to cross barrier; retards GFR
  • increases as plasma diverted into BC
27
Q

Glomerular capillary pressure remains constant as blood moves from the afferent arteriole into the efferent arteriole. What NFP paramter changes

A

the oncotic pressure in the glomerular capillary increases from 20 mmHg in the afferent arteriole to 35 mmHg in the efferent arteriole

28
Q

equation for Net filtration pressure (NFP)

A
  • NFP = (PGC + πBC) - (PBC + πGC)
  • note πBC = 0
29
Q

vasoconstriction of the afferent arteriole has what effect on GFR? Vasoconstriction of the efferent arteriole has what effect on GFR

A
  • afferent: decreases PGC -> Decreases GFR
  • efferent: increases PGC -> Increases GFR
30
Q

what happens to PGC and RBF when afferent and efferent arteriolar resistances both increase

A
  • PGC: no effect
  • RBF: dramatic decrease
31
Q

name a situation which would cause a increase in bowman’s capsule pressure. what effect does this have of GFR

A
  • increase in intratubular pressure due to obstruction of tubule or extrarenal urinary system
  • decrease in GFR

Hum Physiology II (12 decks)

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