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bmsc 208 > renal 2 > Flashcards

renal 2 Flashcards

1
Q

what is filtration?

A

filtration of plasma from the glomerular capillaries into the kidney tubules is the first step in urine formation
-RBCs and plasma proteins remain in the blood, plasma and dissolved solutes make up filtrate
-of all the plasma that enters into the Bowman’s capsule, only 20% is filtered (filtration fraction), 80% continues on to the peritubular capillaries

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2
Q

what is the equation for filtration?

A
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3
Q

what is the renal corpuscle?

A
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4
Q

what is the triple filtration barrier?

A
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5
Q

what are mesangial cell?

A

-supportive and connective tissue cells
-can influence filtration by reducing surface area (by contracting)

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6
Q

what are the three pressures govern filtration from glomerular capillaries into the renal tubules?

A

-hydrostatic pressure
-colloid osmotic pressure
-bowman’s capsule hydrostatic pressure

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7
Q

what is hydrostatic pressure?

A

hydrostatic pressure of blood in the glomerular capillaries favors filtration (55mm Hg) (overall blood pressure)

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8
Q

what is colloid osmotic (oncotic) pressure?

A

colloid osmotic pressure of the blood is the pressure gradient due to the presence of plasma proteins and opposes filtration (30 mmHg)

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9
Q

what is bowmans capsule hydrostatic pressure?

A

(fluid pressure) opposes filtration (15mmHg)

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10
Q

what is GFR?

A

glomerular filtration rate
-the volume of fluid that filters from the glomerular capillaries into the bowman’s capsules per unit time

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11
Q

how much plasma does GFR in a day?

A

-normally 125 ml/min or 180L/day
-our plasma volume is about 3L meaning the kidneys filter our entire plasma volume approximately 60 times per day
-if it was not reabsorbed we would run out of plasma in about 24 minutes

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12
Q

GFR is ____________

A

RELATIVELY CONSTANT
-relatively constant over a wide range of blood pressures

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13
Q

what is GFR primarily regulated by ____________

A

renal arterioles (afferent and efferent)

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14
Q

how does the GFR remain relatively constant?

A

-renal blood flow is dependent on overall resistance, which is determined by the resistance in both the afferent and efferent arterioles
-if afferent arteriole resistance decreased and efferent stayed the same then RBF would increase, hydrostatic pressure increase and GFR increase

REGULATION MAINLY OCCURS AT THE AFFERENT ARTERIOLES

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15
Q

what happens for the GFR to decrease and increase?

A
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16
Q

what is the GFR autoregulation?

A

two auto-regulatory mechanisms maintain a relatively stable GFR in the face of normal blood pressure fluctuations
-to protect the filtration barriers from high blood pressure that would cause damage

17
Q

what are the two mechanisms of autoregulation of GFR?

A

-myogenic response of the afferent arterioles (myogenic autoregulation)
-tubuloglomerular feedback

18
Q

what is myogenic autoregulation?

A

contraction in response to stretch of the vascular smooth muscle

19
Q

what is the graph of myogenic autoregulation?

A
20
Q

what is tubuloglomerular feedback?

A

-local control pathway in which fluid flow through the tubule portion of the nephron influences GFR

21
Q

what is the tubuloglomerular feedback graph?

A

increased NaCl transport in macula densa cells/increased cilia movement

22
Q

what other two factors can influence GFR? and how is it allowed?

A

-sympathetic neurons
-hormones

-integrating centers outside the kidneys are capable of overriding the local control mechanisms by altering resistance or filtration coefficient

23
Q

how can sympathetic neurons influence GFR?

A

-sympathetic neurons release norepinephrine that acts on a1 adrenergic receptors on both afferent and efferent arterioles leading to vasoconstriction
-sympathetic activation only really alters GFR when there is a sharp rapid drop in blood pressure (ex: hemorrhage or severe dehydration when water needs to be conserved)

24
Q

how do hormones influence GFR?

A

-two important hormones that modulate arterioles resistance are angiotensin II, which is a potent vasoconstrictor and prostaglandins, which act as vasodilators
-these hormones are also believed to alter the filtration coefficient by acting on podocytes and/or mesangial cells
-modulation of podocytes changes the size of the filtration slits altering permeability for filtration
-contraction of mesangial cells alters capillary surface area available for filtration

bmsc 208 (32 decks)

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