Physiology 3 (easy)

Question 1

Normal GFR

Answer 1

125ml/min

Question 2

Major determinant of GFR

Answer 2

Glomerular capillary fluid blood pressure

Question 3

Extrinsic regulation of GFR

Answer 3

Sympathetic control via baroreceptor reflex

Question 4

Intrinsic regulation of GFR (autoregulation)

Answer 4

• Myogenic mechanism

- Tubuloglomerular feedback mechanism

Question 5

Does vasoconstriction or vasodilation increase GFR?

Answer 5

Vasodilation

Question 6

What is the myogenic mechanism

Answer 6

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

Question 7

What is the tubuloglomerular feedback mechanism?

Answer 7

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

Question 8

What is the plasma clearance?

Answer 8

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

Question 9

How do you calculate clearance of substance X?

Answer 9

Rate of excretion/plasma concentration

Question 10

What is filtration/secretion/reabsorption of H+?

Answer 10

Filtered, secreted but not reabsorbed

Question 11

Clearance

Answer 11

Reabsorbed

Question 12

Clearance = GFR

Answer 12

Neither reabsorbed or secreted

Question 13

Clearance > GFR

Answer 13

Substance secreted

Question 14

Name an exogenous organic anion used to measure renal plasma flow

Answer 14

Para-amino hippuric acid (PAH)

Question 15

Why use PAH?

Answer 15

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

Question 16

Average renal plasma flow

Answer 16

650ml/min

Question 17

Properties a clearance marker should have

Answer 17

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

Question 18

Should be filtered freely but not secreted or reabsorbed

Answer 18

GFR marker

Question 19

Should be filtered and completely secreted

Answer 19

RPF

Question 20

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

Answer 20

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

-remember roughly 20% is filtered

Question 21

How do you calculate renal blood flow?

Answer 21

RPF x 1/1-Hct

Hct = haemocrit