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Physiology I > Ionic Distributions and Nernst Equation > Flashcards

Ionic Distributions and Nernst Equation Flashcards

1
Q

What creates a diffusion potential

A

concentration difference of an ion across a selectively permeable membrane

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2
Q

what is another name for diffusion potential

A

membrane potential

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3
Q

what way do molecules move in terms of energy

A

from high energy to low energy

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4
Q

what kinds of forces create the energy that drive the movement of molecules

A

chemical
electrical
electrochemical

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5
Q

when a molecule exists in a different concentration on either side of the membrane, there is what across the membrane

A

concentration gradient

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6
Q

what symbol symbolizes the difference in concentration

A

∆C

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7
Q

what is the name of the net force driving molecules down a concentration gradient

A

chemical driving force

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8
Q

chemical driving force is directly proportional to what

A

concentration gradient

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9
Q

the greater the concentration gradient, the greater the

A

force

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10
Q

if there is more than one molecule across a membrane, describe their concentration gradients/driving force

A

they each have their own

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11
Q

when molecules move from area of high concentration to an area of low it results in

A

release of energy

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12
Q

when molecules release energy by going to lower concentration it is described as

A

going down concentration gradient

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13
Q

ions, atoms or molecules w/ charge are affected by what force

A

electrical driving force

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14
Q

if there is no concentration gradient but there are differently charged ions, there will still be

A

electrical driving force, still have movement of ions

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15
Q

membrane potential results from

A

unequal distribution of charges across the membrane

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16
Q

if anions and cations are balanced across the membrane, what is the membrane potential

A

0

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17
Q

what is the unit the membrane potential is measured in

A

mV

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18
Q

what does mV stand for

A

one thousandth of a volt (mili volt)

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19
Q

what is membrane potential for most cells

A

-70 mV

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20
Q

in resting cell, cations are attracted to

A

inside of cell

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21
Q

in resting cell anions are attracted to

A

exterior of cell (outside)

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22
Q

magnitude of electrical force depends on what

A

size of membrane potential

charge of the ion

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23
Q

size of membrane potential & charge of ion determine what

A

magnitude of electrical force

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24
Q

the greater the membrane potential or charge of the ion, the greater the

A

electrical driving force

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25
Q

define the electrochemical driving force

A

total forces acting upon ions, combining chemical and electrical forces

26
Q

the net direction of electorchemical force =

A

sum of both forces

27
Q

the point at which the chemical and electrical forces (if they are going opposite direction) equal each other is the

A

equilibrium potential

28
Q

what does the equilibrium potential of an ion depend on

A

concentration gradient

valence (charge)

29
Q

Eion stands for

A

electrical potential difference

30
Q

The electrical potential difference (Eion) across the membrane required to oppose the concentration force exactly to prevent net diffusion of an ion is called the

A

Nernst or equilibrium potential for that ion.

31
Q

what is the nernst equation (write both versions)

A 
delta u(x) =  RTln[X]A   +    zF(EA - EB)       	            	            
                      [X]B

Eion (mV) = 60 log Co **THIS IS THE ONE TO KNOW
z Ci

32
Q

what is the nernst equation used to determine

A

equilibrium potential of an ion

33
Q

What does R stand for in nernst equation

A

gas constant

34
Q

what does T stand for in nernst equation

A

absolute temperature

35
Q

what does XA stand for in nernst equation

A

concentration of ion X on side A

36
Q

What does XB stand for in nernst equation

A

concentration of ion X on side B

37
Q

what does z stand for in nernst equation

A

valence of ion

38
Q

What does F stand for in nernst equation

A

Faraday’s constant

39
Q

what does EA-EB stand for in nernst equation

A

electrical potential

40
Q

what does ∆u stand for in nernst equation

A

electrochemical potential difference (net force on ion)

41
Q

when chemical and electrical gradients are equal and opposite, ∆u=?
it is said to be in

A

0

electrochemical equilibrium!

42
Q

What does Co = in nernst equation?

A

concentration of ion outside of cell

43
Q

what does Ci = in nernst equation?

A

concentration of ion inside cell

44
Q

If the chemical and electrical forces are in opposite directions and the equilibrium potential > the membrane potential

A

the chemical force is larger and the combined electrochemical force is in the direction of the chemical force.

45
Q

If the chemical and electrical forces are in opposite directions and the membrane potential > equilibrium potential

A

the electrical force is larger and the electrochemical force is in the direction of the electrical driving force

46
Q

draw diffusion potential b/w nerve fiber A and B and explain

A

pg 3 ppt

47
Q

if we were at -94 at nerve fiber A (only permeable to potassium) with no net current, change the electrical driving force (not chemical) to -120 (making membrane potential more neg compared to outside) will there be net current
if there is net current, what direction would potassium move

A

yes - b/c driving force is a different magnitude from chemical driving force
inward potassium current b/c potassium is attracted at more negativity

48
Q

membrane potential is the

A

electrical driving force

49
Q

explain what you are looking at with nernst equation

A

if you have given chemical concentrations, are going to calculate the other driving force (electrical) and be equal opposite

50
Q

Vm =?

A

membrane potential (electrical)

51
Q

log of 100 is

A

2

52
Q

log of 10 is

A

1

53
Q

log of 1000 is

A

3

54
Q

. for any univalent ion if there is tenfold difference need what to oppose it

A

60 mV

55
Q

look at and understand pg 15

A

pg 15

56
Q

look at and understand pg 16

A

16

57
Q

hyperkaeilemia is what

A

outside of cell have higher potassium

increase in extracellular potassium

58
Q

why does potassium have bigger impact on membrane potential than sodium

A

Leak channels. Theres more leak potassium channels present so theres more movement of potassium and it has more of an impact on membrane potential.

59
Q

10 fold difference in univalent ion needs what as the other driving force

A

60 mV as other driving force

60
Q

change in driving force of potassium is going to change by factor of

A

60

Physiology I (9 decks)

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