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Flashcards in Physiology 3 (easy) Deck (21)
1

Normal GFR

125ml/min

2

Major determinant of GFR

Glomerular capillary fluid blood pressure

3

Extrinsic regulation of GFR

Sympathetic control via baroreceptor reflex

4

Intrinsic regulation of GFR (autoregulation)

-Myogenic mechanism
-Tubuloglomerular feedback mechanism

5

Does vasoconstriction or vasodilation increase GFR?

Vasodilation

6

What is the myogenic mechanism

If vascular smooth muscle is stretched, (i.e. arterial pressure is increased), it constricts thus constricting the arteriols

7

What is the tubuloglomerular feedback mechanism?

If GFR rises, more NaCl flows through the tubule leading to constriction of afferent arterioles

8

What is the plasma clearance?

A measure of how effectively the kidneys can 'clean' the blood of a substance

9

How do you calculate clearance of substance X?

Rate of excretion/plasma concentration

10

What is filtration/secretion/reabsorption of H+?

Filtered, secreted but not reabsorbed

11

Clearance

Reabsorbed

12

Clearance = GFR

Neither reabsorbed or secreted

13

Clearance > GFR

Substance secreted

14

Name an exogenous organic anion used to measure renal plasma flow

Para-amino hippuric acid (PAH)

15

Why use PAH?

-freely filtered
-secreted into tubule
-completely cleared from plasma

16

Average renal plasma flow

650ml/min

17

Properties a clearance marker should have

Non-toxic
Inert (i.e. not metabolised)
Easy to measure

18

Should be filtered freely but not secreted or reabsorbed

GFR marker

19

Should be filtered and completely secreted

RPF

20

What is the filtration fraction and how do you calculate it?

The fraction of plasma flowing through the glomeruli that is filtered into the tubules
(GFR/renal plasma flow)

-remember roughly 20% is filtered

21

How do you calculate renal blood flow?

RPF x 1/1-Hct

(Hct = haemocrit)