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Neuroscience > Chapter 2 Resting potential > Flashcards

Chapter 2 Resting potential Flashcards

1
Q

simply a device that separates positive and negative

charges

A

battery

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2
Q

The separation of charges

is due to two major things. Please enumerate

A

First is that there is an imbalance of various ions on the inside compared to the outside
of the cell.

Inside, more K
Outside, more Na

Second is that the cell membrane is semipermeable

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3
Q

simply means that
the membrane has pores or channels that allow only certain molecules to pass while preventing
others from crossing from one side to the other.

A

Semipermeable

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4
Q

The semipermeable membranes of all cells

allow _____ ions to pass through easily

A

K+ ions

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5
Q

The semipermeable membranes of all cells

allow K+ ions to pass through easily, but act as barriers for the passage of

A

Na+, Cl-, and Ca++ ions.

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6
Q

law of diffusion

A

that all molecules move
from a region of higher concentration to a region of lower concentration, and will continue to do
so until the concentrations become equal throughout.

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7
Q

In other words, there are

two opposing forces acting on K+ ions;

A

the concentration force driving K+

electrical force driving K

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8
Q

In other words, the net movement of K+ across the membrane will cease when

A

the two

opposing forces acting on K+ are equal

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9
Q

ccurs when the
concentration force tending to drive K+ from left to right is exactly balanced by the electrical force
tending to attract K+ from the right back into the left compartment.

A

equilibrium

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10
Q

This electrical force, or

electrical potential, that counterbalances the concentration force is called the

A

equilibrium potential for that ion.

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11
Q

the greater the
concentration difference for the permeable ion, K+ in this case, the more _____ the left
compartment has to be to counteract the concentration force

A

more negative

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12
Q

is a statement of the equilibrium condition for a single ion species
across a membrane that is permeable only to that ionic species.

A

Nernst Equation

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13
Q

Nernst equation tell you

A

what electrical force (electrical potential E in equation below) has to act on that ion in
order to exactly balance the concentration force acting on the same ion.

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14
Q

The E in the Nernst equation is referred to as the

A

equilibrium

potential for the ion

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15
Q

is the potential at which equilibrium is attained

A

equilibrium

potential for the ion

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16
Q

Cell membranes are impermeable to large organic anions existing inside the
cell, such as

A

aspartate, isothionate, and other amino acids as well as proteins

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17
Q

All Cells have a Resting Potential Determined Largely by

A

Potassium

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18
Q

Nernst Equation is

A

58/z log (ion ouside/ ion inside)

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19
Q

in squit, K+ concentration in the interstitial

(extracellular) fluid is

A

20 mM

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20
Q

squid : K+ concentration inside the cell

A

400 mM.

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21
Q

The actual resting potential of the squid giant axon can be accurately measured and is only
about

A

-70 mV.

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22
Q

is the electrical state of the cell (the voltage across its

membrane) when it is not active and thus not generating action potentials.

A

resting membrane potential

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23
Q

The reason that the actual resting potential of the cell is not equal to Ek is that

A

both Na+ and
Cl- play a small role in determining the electrical state of the cell (the cell’s resting potential).

The membrane is not absolutely impermeable to Na+.

24
Q

force/s that drive Na into the cell

A

concentration

and electrical forces

25
Q

[Na]o

A

450 mM

26
Q

[Na]i

A

50 mM

27
Q

ENa

A

+55 mv

28
Q

Ek,

A

-70 mV

29
Q

Based on

concentrations of Cl-, the Nernst equation tells us that the equilibrium potential for Cl-

A

-67 mV

30
Q

The Concentration Gradients of All Ions Should Run Down but the cell has a means to combat this problem which is

A

it has sodium-potassium pumps.

31
Q

The pump is open to the intracellular fluids and ____ are bound to protein

A

3 Na+ are bound to the protein.

32
Q

The pump has ATPase activity and the binding of Na+ causes the

A

hydrolysis of ATP to ADP+Pi.

33
Q

Inorganic Pi binds to the pump leads to

A

changing its configuration. The change in shape then allows
the release of Na+ into the extracellular space.
also allows the protein to bind 2 K+.

34
Q

binding of K+ to N-K pump causes

A

de-phosphorylation of the protein, which then causes the protein to
18
assume its original shape, which then transfers the K+ across the membrane and releases it into the
intracellular fluid.

35
Q

Na-K pump also known as

A

Na-K

ATPase

36
Q

utilizes the energy stored in ATP to actively transport Na+ out of the cell and K+ into
the cell (note that this transport is active because it occurs against concentration gradients-that is,
the protein transports Na+ and K+ ions from regions where they have low concentrations to
regions were they have high concentrations).

A

Na-K

ATPase

37
Q

In its normal operation, the pump

transports ________ for each ATP molecule utilized.

A

2K+ ions into the cell and 3 Na+ ions out of the cell

38
Q

Thus, the Na-K pump itself is actually separating charges because it pumps more positive Na+
charges out of the cell than it pumps K+ into the cell. In such cases the operation of the pump is
said to be

A

electrogenic

39
Q

do not establish the resting potential, but rather their
purpose is to maintain the concentration gradients so that neurons can retain their resting
potentials even though they continuously lose K+ and continuously gain Na+.

A

Na-K pump

40
Q

this drug inhibits the activity of this Na-K pump

A

ouabain

and digitalis

41
Q

The Resting Potential is given by this equation

A

Goldman-Hodgkin-Katz Equation

42
Q

thi ion has the greatest permeability, it receives the greatest weight and thus makes the largest
contribution to RMP

A

K+

43
Q

is much less permeable and contributes only slightly to the resting potential.

A

Na+

44
Q

The calculation of the resting potential can be made from the

A

Goldman-Hodgkin-Katz

(GHK) equation

45
Q

The membrane potential computed from the GHK equation is

A

-70.18 mV

46
Q

electrical state of the cell when it is not receiving inputs from other cells (when it is at rest).

A

resting potential

47
Q

large change in membrane potential

A

action potential

48
Q

when the membrane potential,

indicated by the symbol Vm, is more positive than the resting potential

A

cell is considered to be depolarized

49
Q

when the membrane potential, Vm, is more negative than the resting potential

A

hyperpolarized

50
Q

is the difference between the concentration and electrical

forces.

A

net strength

51
Q

`The resting potential exists because of

A

oncentration differences of Na+, K+, and Cl- across

the semi-permeable membrane.

52
Q

The major determinant of the resting potential

A

K+

53
Q

Although K+ is considered the primary ion underlying the resting membrane potential, the
actual resting potential will not equal EK because

A

Na+ continuously leaks

into the cell

54
Q

The exact magnitude of the resting membrane potential thus depends on the weighted
contributions of the several ions moving across the membrane, expressed formally by the

A

the

Goldman-Hodgkin-Katz equation.

55
Q

required to maintain (note maintain, not generate) RMP

A

Na+ - K+ exchange pump

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