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Flashcards in Physiology Deck (46):
1

Define Osmolarity

Concentration of osmotically active particles present in a solution

2

What 2 factors are required to allow you to calculate osmolarity?

Molar concentration of the solution
Number of osmotically active particles present

3

Define tonicity?

The effect a solution has on cell volume
e.g. hypotonic isotonic etc

4

What are the two major body compartments that water exists in?

Intracellular Fluid
Extracellular Fluid

5

Which compartment makes up more of the total body water?

Intracellular

6

Which compartment do interstitial fluid, lymphatic fluid and plasma belong to?

Extracellular Fluid

7

What is a fluid shift?

This is when there is movement of water between the ICF and the ECF in response to an osmotic gradient

8

What alters the composition and volume of the ECF

Kidneys

9

These are major contributors to the osmotic concentrations of the ECF and ICF and directly affect the functioning of all cells

Na +
K +

10

Where is sodium mainly present?

ECF

11

Name two detrimental consequences caused by a fluctuation in K+ levels?

Cardiac Arrest
Muscle paralysis

12

What plays a key role in establishing membrane potentials?

Potassium

13

What are tracers used for?

They are used to help calculate volume of the body fluid compartments

14

What tracer is used to calculate TBW

3H2O

15

What is inulin used for

ECF

16

Labelled albumin can be used to detect what?

Plasma Volume

17

Give at least 5 funtcions of the kidney?

Water balance
Salt balance
Acid-base balance
Maintenance of plasma volume
Maintenance of plasma osmolarity
Excretion of metabolic waste
Excretion of exogenous foreign compounds
Secretion of renin
Secretion of eythropoietin
Conversion of vit D to active form

18

What is responsible for the mechanisms of filtration, re-absorption and secretion within the kidney?

The nephron

19

What is the role of the renal tubule?

Acts as a 'conveyor belt' where substances are removed or added while the urinary filtrate moves from proximal to distal

20

How much of the plasma which enters the glomerulus is not filtered and leaves via the efferent arteriole?

80%

21

Equation to calculate the rate of filtration

Rate of filtration of X = [X] plasma x GFR

(GFR= glomerular filtration rate)

22

Equation to calculate the rate of excretion

Rate of Excretion = [X] x Vu

(where Vu = urine flow rate )

23

Equation to calculate the rate of re-absorption

Rate of re-absorption =
Rate of filtration - rate of excretion

24

What does rate of excretion - rate of filtration calculate?

The rate of secretion of a substance

25

What is the rate of glomerular filtration?

125ml/min

26

Where is the majority of filtered fluid reabsorbed?

Proximal tube of nephron

27

What type of molecules are reabsorbed in the proximal tube

Sugars
Amino Acids
Phosphate
Sulphate
Lactate

28

What does the proximal tube secrete?

H+
Hippurates
Neurotransmitters
Bile Pigments
Uric Acid
Drugs
Toxins

29

Two methods of re-absorption in the proximal tubule?

Transcellular
Paracellular

30

What methods of membrane transport does Na+ use?

Diffusion through channels
Primary active transport
Secondary Active transport

31

What energy dependent transport mechanism is essential for Na+ re-absorption?

Na+ K+ ATPase

32

The re-absorption of Na+ leads to the passive absorption of what?

Chloride Ions

33

What does the absorption of Na+Cl- cause?

An osmotic gradient, leading to passive water absorption
i.e. osmosis

34

What is normally 100% absorbed in proximal tubule?

Glucose
(and amino acids)

35

The tubule is iso-osmotic? True or False

True

36

What is the function of the loop of Henle?

To generate a cortico-medullary solute concentration enabling the formation of hyper-tonic urine

37

Which part of the Loop of Henle is permeable ONLY to water and NOT to salts

Descending Limb

38

Which part of the Loop of Henle is NOT permeable to water but is permeable to salts (NaCl)

Ascending Limb

39

How does the differences in permeability between ascending and descending limbs affect the medulla?

It establishes an osmotic gradient

40

What transports ions out of the lumen?

The triple co transporter
Transports Na+ K+ and Cl-

41

What drug class blocks the triple co-transporter?

Loop Diuretics

42

When is the fluid hypo-osmotic?

When it enters the distal tubule (after leaving the ascending loop)

43

What substance passively diffuses into the loop and is responsible for half of the medullary osmolality?

Urea
(Note the distal tubule is not permeable to urea)

44

What is the purpose of counter-current multiplication?

To concentrate the medullary interstitial fluid

45

Why does the countercurrent multiplication need to concentrate the medullary IF?

To enable the kidney to alter the volume and concentration of urine based on ADH (vasopressin) release

46

What is the vasa recta?

A specialized capillary which runs alongside the loop of Henle which acts as a counter-current exchanger