Membrane potential III

Question 1

There is an excess of negative charge inside of the cell that gives rise to a

Answer 1

resting negative potential.

the potential difference resulting from this imbalance is large, the actual difference in the number of cations versus anions inside the cell is relatively small.

Question 2

the number of excess anions in a typical cell is _____ compared to the total number of _____.

Answer 2

small

anions

Question 3

bulk solutions are always electrically _____.

Answer 3

neutral

Question 4

Principle of Electrical Neutrality states that

Answer 4

bulk solutions have equal concentrations of anions and cations.

Question 5

Equilibrium, in the case of ions, depends on

Answer 5

differences in both ion concentration and in electric potential between the inside of the cell and the extracellular fluid.

Question 6

Equilibrium is achieved when a balance

Answer 6

between the concentration gradient and the electric gradient is reached.

Question 7

Nernst equation:

Answer 7

E=(60/z) log (Coutside/Cinside)

Question 8

Osmotic balance

Answer 8

osmolarity between the inside and outside of the cell must be equal

Question 9

charge neutrality

Answer 9

the concentration of anions must equal that of cations in both the intra and extra cellular fluids

Question 10

Nernest equations explains that

Answer 10

when dealing with ions, the effect of charge and electric force must be considered

Question 11

Dannons rule is

Answer 11

when two permeating ions are, the equilibrium potential (E) must satisfy both ions.

Question 12

Dannon’s rule equation is

Answer 12

[K+]outside x [Cl-]outside =[K+]inside x [Cl-]inside

Question 13

With each cycle of the sodium pump, ____ K+ ions are pumped into the cell and ____ Na+ ions are pumped out of the cell. This is accomplished with energy from the ____

Answer 13

two

three

splitting of ATP.

Question 14

Equilibrium is a state in

Answer 14

which no energy is required to move ions across membranes to maintain the state.

Question 15

Even if the concentrations are not the same on both sides of the membrane, for every ion that comes into the cell

Answer 15

another will leave without net use of energy.

Question 16

In contrast, a steady state requires an input of energy to maintain

Answer 16

the composition of the ICF.

This constant input of energy is derived from metabolism. Like equilibrium, the concentrations of ions are not changing over time.

Question 17

membrane potential depends on

Answer 17

relative, not absolute, permeabilities to ions.

Question 18

Different cells throughout the body have different membrane potentials, this is due to

Answer 18

differences in the relative permeability of ions in these cells.

Question 19

K ions and Na ions are always struggling to attain their equilibrium potential, and how close they can come depends on the

Answer 19

relative number of channels for that ion.

Question 20

A glial cell has very few ___ channels compared to __ channels, so it is essentially permeable only ____, thus the membrane potential of these cells is very close to the ____

Answer 20

Na

K

to K

Ek

Question 21

The Na/K pump has a maximum rate cannot be

Answer 21

significantly adjusted, thus it is integral in establishing long term stability of membrane potential but not the short term changes in potential.

Question 22

the primary short term determinant of membrane potential is not the Na/K pump, but the:

Answer 22

relative membrane permeabilities to the different ions.

Question 23

what determines short term membrane potential?

Answer 23

The amount of a given ion flowing across the membrane

a cell that is very leaky to K and Na ions can have the same membrane potential as a cell that is tight, if the cells have the same proportion of ion channels, so the relative number of ions moving is the same.

Question 24

The driving force of an ion is the:

Answer 24

the difference between membrane potential and the equilibrium potential of that ion

driving force is the extent to which an ion wants to enter a cell.

Question 25

Neurons and other excitable cells, potential is sensitive to small changes in ____ but not _____

Answer 25

[K+]o,

[Na+]o

Question 26

Changes in the ECF concentration of Na have little effect on cells because:

Answer 26

the membrane is relatively impermeable to Na

Question 27

changes in Na concentration have little to no effect on:

Answer 27

membrane potentials.

Question 28

____ is the dominant cation in the ECF.

Answer 28

Na

Question 29

Because there isn’t very much K in the ECF, An increase in ECF concentration of K will result in

Answer 29

less efflux of K ions from the cell.

So small changes in extracellular concentration can greatly affect membrane potential.

Question 30

Concerning hyperkalemia:

1. Name the most common source of the extra potassium
2. One important sign
3. Two major strategies for reducing the potassium concentration in the ECF.

Answer 30

ICF

EKG change

uptake by cells and removal from body.