Chapter 2 Resting potential

Question 1

simply a device that separates positive and negative

charges

Answer 1

battery

Question 2

The separation of charges

is due to two major things. Please enumerate

Answer 2

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

Question 3

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.

Answer 3

Semipermeable

Question 4

The semipermeable membranes of all cells

allow _____ ions to pass through easily

Answer 4

K+ ions

Question 5

The semipermeable membranes of all cells

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

Answer 5

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

Question 6

law of diffusion

Answer 6

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.

Question 7

In other words, there are

two opposing forces acting on K+ ions;

Answer 7

the concentration force driving K+

electrical force driving K

Question 8

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

Answer 8

the two

opposing forces acting on K+ are equal

Question 9

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.

Answer 9

equilibrium

Question 10

This electrical force, or

electrical potential, that counterbalances the concentration force is called the

Answer 10

equilibrium potential for that ion.

Question 11

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

Answer 11

more negative

Question 12

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

Answer 12

Nernst Equation

Question 13

Nernst equation tell you

Answer 13

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.

Question 14

The E in the Nernst equation is referred to as the

Answer 14

equilibrium

potential for the ion

Question 15

is the potential at which equilibrium is attained

Answer 15

equilibrium

potential for the ion

Question 16

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

Answer 16

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

Question 17

All Cells have a Resting Potential Determined Largely by

Answer 17

Potassium

Question 18

Nernst Equation is

Answer 18

58/z log (ion ouside/ ion inside)

Question 19

in squit, K+ concentration in the interstitial

(extracellular) fluid is

Answer 19

20 mM

Question 20

squid : K+ concentration inside the cell

Answer 20

400 mM.

Question 21

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

Answer 21

-70 mV.

Question 22

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

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

Answer 22

resting membrane potential

Question 23

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

Answer 23

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+.

Question 24

force/s that drive Na into the cell

Answer 24

concentration

and electrical forces

Question 25

[Na]o

Answer 25

450 mM

Question 26

[Na]i

Answer 26

50 mM

Question 27

ENa

Answer 27

+55 mv

Question 28

Ek,

Answer 28

-70 mV

Question 29

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

Answer 29

-67 mV

Question 30

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

Answer 30

it has sodium-potassium pumps.

Question 31

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

Answer 31

3 Na+ are bound to the protein.

Question 32

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

Answer 32

hydrolysis of ATP to ADP+Pi.

Question 33

Inorganic Pi binds to the pump leads to

Answer 33

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+.

Question 34

binding of K+ to N-K pump causes

Answer 34

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.

Question 35

Na-K pump also known as

Answer 35

Na-K | ATPase

Question 36

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).

Answer 36

Na-K | ATPase

Question 37

In its normal operation, the pump | transports ________ for each ATP molecule utilized.

Answer 37

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

Question 38

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

Answer 38

electrogenic

Question 39

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+.

Answer 39

Na-K pump

Question 40

this drug inhibits the activity of this Na-K pump

Answer 40

ouabain | and digitalis

Question 41

The Resting Potential is given by this equation

Answer 41

Goldman-Hodgkin-Katz Equation

Question 42

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

Answer 42

K+

Question 43

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

Answer 43

Na+

Question 44

The calculation of the resting potential can be made from the

Answer 44

Goldman-Hodgkin-Katz | (GHK) equation

Question 45

The membrane potential computed from the GHK equation is

Answer 45

-70.18 mV

Question 46

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

Answer 46

resting potential

Question 47

large change in membrane potential

Answer 47

action potential

Question 48

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

Answer 48

cell is considered to be depolarized

Question 49

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

Answer 49

hyperpolarized

Question 50

is the difference between the concentration and electrical | forces.

Answer 50

net strength

Question 51

`The resting potential exists because of

Answer 51

oncentration differences of Na+, K+, and Cl- across | the semi-permeable membrane.

Question 52

The major determinant of the resting potential

Answer 52

K+

Question 53

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

Answer 53

Na+ continuously leaks | into the cell

Question 54

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

Answer 54

the | Goldman-Hodgkin-Katz equation.

Question 55

required to maintain (note maintain, not generate) RMP

Answer 55

Na+ - K+ exchange pump