7. Glomerular Filtration and Renal Blood Flow

Question 1

For the starling forces in the glomerulus and bowman’s capsule, the osmotic pressure in the bowmans capsule ( Pi BC) is normally zero. What are the other 3 forces?

Answer 1

Glomerular hydrostatic pressure favors filtration
Bowmans capsule hydrostatic pressure (PBC) opposes filtration
Glomerular capillary osmotic pressure (Pi GC) opposes filtration (absorption)

Question 2

What is the calculation for filtration?

Answer 2

Kf (Pgc - Pbc - Pi gc)

Question 3

what means the same as colloid osmotic pressure?

Answer 3

oncotic pressure

Question 4

The ultrafiltration coefficient (Kf) can be calculated by multiplying hydraulic conductivity (permeability/#pores in endothelium) Lp and?

Answer 4

surface area for filtration (Sf)

Question 5

The two factors involved in calculating Kf (Sf and Lp) multiplied by the PUF (capillary ultrafiltration pressure or the starling forces) will equal?

Answer 5

GFR

so if Lp or Sf increase, so does GFR
If PUF increases so does GFR

Question 6

What three things can alter the Pgc?

Answer 6

renal arterial blood pressure
afferent arteriolar resistance
efferent arteriolar resistance

Question 7

The ultrafiltration coefficient (Kf) only changes due to kidney disease and deficiency in glycocalyx. What role do the glomerular mesangial cells play in the ultrafiltration coefficient?

Answer 7

glomerular mesangial cells contract, which influences/ decreases the glomerular surface area, which decreases GFR

Question 8

Hydrostatic pressure is highest in the renal artery and lowest in the renal vein (normal). Where are the two sites of regulation, seen by a large drop in pressure due to fluid getting filtered out?

Answer 8

at the afferent and efferent arterioles where fluid is filtered out

** relatively high hydrostatic P in glomerular capillary**

Question 9

When the fluid is being filtered out leaving all the plasma proteins in the blood, this increase its concentration leading to an increase in what ?

Answer 9

oncotic GC (Pi gc)

Question 10

At the afferent arteriole, Pgc and Pigc are 60 and 25 respectivley, but at the glomerular capillary and efferent arteriole, what occurs?

Answer 10

the oncotic gc pressure increases d/t increase in plasma concentration and the hydrostatic gc will drop only 1-2mmHg

Question 11

PUF (filtration) remains greater when the blood flow is higher and more of the glomerular capillary is exposed to a net driving force for filtration, which increases?

Answer 11

surface area for filtration

Question 12

When there is constriction at the afferent arteriole what occurs to the GFR and PUF (starling forces)?

Answer 12

gfr and puf will decrease

Question 13

When there is dilation at the afferent arteriole what occurs to the gfr and puf?

Answer 13

gfr and puf will increase

Question 14

When there is constriction at the efferent arteriole what occurs to the gfr and puf?

Answer 14

gfr and puf will increase

Question 15

When there is dilation at the efferent arteriole what occurs to the gfr and puf?

Answer 15

gfr and puf will decrease

Question 16

During any dilation and constriction what will occur to renal blood flow?

Answer 16

during dilation at either afferent or efferent, the RBF will increase as opposed to during constriciton RBF will decrease in both.

Question 17

The kidney consumes about 7 times more blood compared to the brain… this is due primarily to?

Answer 17

O2 consumption which is related to the high Na+ reabsorption in the tubules (possitive correlation)

Question 18

What are three physiological controls of glomerular filtration and rbf, more focused on changing glomerular hydrostatic pressure and glomerular capillary oncotic pressure?

Answer 18

1. vasoactive signals
2. hormones
3. sympathetics

Question 19

Intrinsic control of the kidney occurs via what two mechanisms?

Answer 19

autoregulation

tubuloglomerular feedback

Question 20

Extrinsic control (bigger/systemic things) of the kidney occurs via what three mechanisms?

Answer 20

sympathetic nerves
hormones
composition of blood

Question 21

Renal blood vessels are richly innervated by sympathetics with strong stimuli which constrict arterioles and decrease rbf/gfr. Local sympathetics and circulating catecholamines active ______ receptors, which are more prevelent in the ______ arteriole.

Answer 21

Alpha 1 receptors which are more prevelent in the afferent arterioles

Question 22

PGE2 (increases rbf), NO (increase rbf), ANP (increase gfr) and what other two are common vasodilators of arterioles?

Answer 22

bradykinin (increases both) and dopamine (increases rbf)

Question 23

Glomerulartubular balance increases reabsorption rate within the renal tubes when ?

Answer 23

GFR rises (= inc Na)

Question 24

Autoregulation maintains rbg and gfr wihtin narrow limits across wide ranges of blood pressures. The local reflex (myogenic) cause smooth muscle contraction to inc BP, while the tubuloglomerular feedback does what?

Answer 24

physiological feedback via juxtaglomerular apparatus (JGA)

changes in tube, feeback to glomerulus

Question 25

bloodflow autoregulation maintains a stable GFR during what range of arterial pressure changes?

Answer 25

80-170mmHg
below 80 gfr/rbf dec
above 170 gfr same and rbf inc.

Question 26

The local myogenic reflex senses and resists stretch due to high blood pressure and smooth m contracts in 1-2s. What is more common at the afferent compared to efferent?

Answer 26

afferent arteriolar experiences more constriction while the efferent experiences dilation

Question 27

The tubuloglomerular feedback uses the juxtaglomerular apparatus which consists of what 3 things?

Answer 27

1. macula densa cells
2. juxtaglomerular (granular) cells - renin
3. Extraglomerular mesangial (lacis) cells

Question 28

The tubuloglomerular feedback sense the concentration of NaCl/ salt in the blood. it feeds back signal to adjust arteriolar resistance as needed when salt is too high/low. What do the macula densa do?

Answer 28

signal to JG cells when decrease Nacl to release renin and talked to the glomerulus when salt is too high to lessen the amount of blood intake

Question 29

What is the main job of the tubuloglomerular feeback ?

Answer 29

to maintain constant Na delivery to the distal convoluted tubule and maintain a constant GFR

Question 30

The macula densa signaling has 4 major steps. The first is increased delivery of NaCl to macula densa tranported via NaCl2K (nKCC2) which leads to an increase in ATP and adenosine. what are steps 3 and 4?

Answer 30

the increase in ATP signals vasoconstriction of the afferent arteriole which decrease GFR so there is less Na in the distal tubule.

Question 31

What occurs when there is an increased renal perfusion pressure?

Answer 31

signals via macula densa results in vasoconstriction of afferent arteriole to decrease GFR, mediated by adenosine

Question 32

What occurs when there is a decreased renal perfusion pressure?

Answer 32

Decreased gfr, decrease NaCl delivery to macula densa, signals to JG to secrete renin, makes angiotensinII to restore BP.
*Results in efferent arteriolar vasoconstriction and afferent arteriolar dilation via NO

Question 33

What are factors that increase sensistivity of TGF (tubuloglomerular feedback)? (5)

Answer 33

volume contraction
adenosine
PGE2
thromboxane
Ang II

Question 34

What are factors that decrease sensistivity of TGF? (6)

Answer 34

volume expansion
ANP
NO
cAMP
PGI2
High protein diet (in Nacl reabsorption so flow)

Question 35

Afferent arteriole vasodilation via protaglandins, bradykinin, NO, dopamine and ANP results in what regarding rbf, gfr and peritubular capillary hydrostatic pressure?

Answer 35

increases gfr rbf and P

Question 36

Afferent arteriole vasoconstriction via ace-inhibitors causes?

Answer 36

rbf, gfr, and peritubular pressure to decrease

Question 37

Efferent arteriole vasodilation via sympathetics causes?

Answer 37

rbf to increase, gfr to decrease and peritubular pressure to increase

Question 38

Efferent arteriole vasoconstriction via angiotensinII causes?

Answer 38

decrease in rbf, increase or same gfr, and decrease in peritubular pressure (hydrostatic)