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

Normal GFR

A

125ml/min

2
Q

Major determinant of GFR

A

Glomerular capillary fluid blood pressure

3
Q

Extrinsic regulation of GFR

A

Sympathetic control via baroreceptor reflex

4
Q

Intrinsic regulation of GFR (autoregulation)

A
  • Myogenic mechanism

- Tubuloglomerular feedback mechanism

5
Q

Does vasoconstriction or vasodilation increase GFR?

A

Vasodilation

6
Q

What is the myogenic mechanism

A

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

7
Q

What is the tubuloglomerular feedback mechanism?

A

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

8
Q

What is the plasma clearance?

A

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

9
Q

How do you calculate clearance of substance X?

A

Rate of excretion/plasma concentration

10
Q

What is filtration/secretion/reabsorption of H+?

A

Filtered, secreted but not reabsorbed

11
Q

Clearance

A

Reabsorbed

12
Q

Clearance = GFR

A

Neither reabsorbed or secreted

13
Q

Clearance > GFR

A

Substance secreted

14
Q

Name an exogenous organic anion used to measure renal plasma flow

A

Para-amino hippuric acid (PAH)

15
Q

Why use PAH?

A
  • freely filtered
  • secreted into tubule
  • completely cleared from plasma
16
Q

Average renal plasma flow

A

650ml/min

17
Q

Properties a clearance marker should have

A

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

18
Q

Should be filtered freely but not secreted or reabsorbed

A

GFR marker

19
Q

Should be filtered and completely secreted

A

RPF

20
Q

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

A

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

-remember roughly 20% is filtered

21
Q

How do you calculate renal blood flow?

A

RPF x 1/1-Hct

Hct = haemocrit