# Session 2 Renal Physiology Flashcards Preview

## CPR Exam 2 > Session 2 Renal Physiology > Flashcards

Flashcards in Session 2 Renal Physiology Deck (23)
1
Q

find Urine Excretion Rate

A

Urine Excretion Rate=Ux x V

Ux=urine amount of X/urine Volume of X

V=urine volume/time collected

2
Q

Example Problem for urine excretion rate

If a patient has a creatinine clearance of 90ml/min, a urine flow rate of 1ml/min, a plasma K concentartion of 4mEq/L, a urine K concentartion of 60mEq/L, what is the approx. K excretion?

Watch units because she wants to make this harder than it has to be

A

Urinary Concentatration of K=Ux=60mEq/L

Urinary Flow Rate=V=1ml/min

Convert 60mEq/L to mEq/ml and multiply times V

(60mEq/1000ml)x(1ml/min)=0.06mEq/min

3
Q

How to calculate GFR?

A

Renal Clearance Equation if using creatinine or inulin

Cx=Ux x V/Px

Uinulin and Pinulin

4
Q

Example Problem for renal clearance/GFR

Inulin is used in an experiement to measure the glomerular filtration rate. Inulin is infused to achieve a steady state concentration in the plasma of 1.0mg/dl. Urine is collected over a 10 hour period. The total volume of urine is 1.5 L and urinary concetration of inulin is 440mg/dl. What is GFR as determined from inulin clearance?

Watch units because she obviously knows how good we are at math based on the results of Quiz 2 and wants to up the anty

A

Cx=Ux x V/Px

Uinulin=440mg/L

V=1.5 L over 10 hours=1.5L/600min=.0025L/min

Pinulin=1.0

Cx=440x0.0025/1=1.1dl/min=110ml/min

5
Q

If filtration fraction increases, do you expect oncotic pressure in the capillaries (Pic) to increase or decreases?

A

Increase

6
Q

Filtered Load is not the same as filtered fraction

A

filtered load is a rate in mg/min

filtered fraction is the ratio of GFR/RBF

7
Q

Why do we care about starling forces on the efferent arteriole and peritubular capillary?

A

Starling forces and changes on the capillaries and efferent arteriole effects what passes through the PCT where 90% of reabsorption happens.

The efficacy of reabsorption in the PCT depends on the starling forces at the peritubular caps. and eff. arteriole

8
Q

What are the intrinsic mechanisms of renal hemodynamics?

What are the extrinsic mechanisms of renal hemodynamics?

A

Autoregulation (myogenic reflex) and tubuloglomerular feedback

SNS, hormones (RAAS), blood composition

9
Q

What is the function of the JG apparatus?

A

macula dense and JG cells sense NaCl in the DCT

signals are sent between the two groups of cells

feeds back and adjusts arteriolar resistance as needed

renin is released as needed

maintains Na delivery to the distal tubule and constant GFR

see Ninja Nerd for details.

10
Q

What is the effect of increased NaCl delivery to macula densa

A
1. increase delivery of NaCl to macula densa
2. Na reabsorbed via NKCC2
3. Stimulates ATP/adenosine signaling
4. stimulates calcium signaling in sm. m. around aff. arteriole causing vasoconstriction
5. this stimulates decrease GFR and decrease in Renin
11
Q

What is the effect when there is a decrease in NaCl to the macula Densa?

A
1. decreased NaCl delivery to macula densa
2. less Na reabsorbed via NKCC2
3. Less ATP/adenosine released
4. Ca not released to sm. m surrounding afferent arterioles
5. aff. arterioles relax
6. increases GFR and renin
12
Q

When NaCl is delivered to the distal tubule, what else happesn?

A
1. decrease in distal solute delivery activates the tubuloglomerular feedback mechansim
2. buffering changes to increase GFR and RBF back towards normal
3. buffering is done by dilating afferent arteriole (from PGE2 and NO and decreased ATP/adenosine)
4. Renin secretion is increased by NaCl delivery as well as by a decrease in renal pressure or increased SNS (from low BV) and makes ang II to constrict eff. arteriole
13
Q

Vasoconstrictors

Vasodilators

A

sympathetics (catecholamines)

endothelin

angiotensin II

Prostaglandins

NO

Dopamine

ANP

ACE inhibitor (lowers GFR)

14
Q

Ang II acts primarily where and does what?

A

acts on efferent arteriole and rasies GFR during diminished renal perfusion

ACE inhibitors (inhibit this) and lower GFR

15
Q

Strong SNS stimulation constricts arterioles and decreases what?

A

GFR/RBF

local sympathetics and catecholamines act on a1 receptors (moreso on afferent than efferent)

16
Q

Angiotensin II decreases RBF how?

A

constricts efferent arteriolar vasoconstriction (you get more blood backing up and pushing out through glomerulus but the rest of the kidney gets less blood as a result)

17
Q

Ang II increases peritubular capillary oncotic pressure and decreases peritubular capillary hydrostatic pressure. Why?

A
1. GFR increases
2. more fluid is filtered from glomerular capillary into the tubular system
3. less fliuid passes on into the peritubular capillaries
4. proteins are more concentrated as a reuslt
5. oncotic pressure increases

FF=GFR/RBF thus here FF increases

18
Q

Afferent arteriole constrictions (plaque in arteriole mimics this) results in what?

A

decreased GFR, decreased NaCl to macula densa

causes macula densa and JG cells to secrete renin and make Ang. II constricting efferent arteriole

this results in afferent arteriolar dilation mediated by NO

19
Q

Assume a clinical trial was conducted in which the investigators succeeded in producing approx. step changes in real function parameters with rapid extracellular volume expansion. This produced an increase in solute delivery to the macula densa. Which of the following is most likely to occur as a result of increased solute delivery to the distal convoluted tubule?

A

Increase in afferent arteriole tone

20
Q

Someone is in acute renal failure. Their GFR is 30, serum creatinine is 1.9. What will decrease the creatinine in her blood?

A

dilating the renal afferent arteriole

21
Q

someone in chronic resistant hypertension is treated with Ca channel antagonist to decrease resistance of the glomerular afferent arterioles. What will also decrease?

A

renin release

22
Q

a 34 year old with diarrhea loses ECF volume. stretch receptors sense that he is dehydrated. What is happening?

A

increase in sympathetic tone

increase in Ang. II

Decrease in ANP

Increase in Plasma oncotic pressure

23
Q

The dehydrated diarrhea boy is given fluid but he is overhydrated. Now the glomeruloartubular balance mechanisms in the PCT need to help eliminate the fluid. What is happening?

A

increase in GFR

increase in peritubular capillary hydrostatic pressure

decrease in peritubular capillary oncotic pressure