Dr. Karius' Vm lecture

Question 1

Resting membrane potential of all living cells is

Answer 1

lower than outside

Question 2

Vm is the

Answer 2

difference of electrical potential between inside and outside cell and right at the membrane itself

Question 3

if a cell’s Vm is 0 that means there is

Answer 3

no difference between the inside and the outside of the cell

Question 4

-90 and +90 Vm mean

Answer 4

the two charges are equal in magnitude but opposite in polarity

Question 5

hyperpolarization =

Answer 5

the membrane potential becomes more negative (moves farther away from zero)

Question 6

Depolarization =

Answer 6

the membrane potential becomes less negative (moves closer to zero)

Question 7

an ionic gradient exists when two conditions are met

Answer 7

1) there is an electrical gradient and

2) there is a chemical gradient working a particle

Question 8

an ionic equilibrium may be achieved when

Answer 8

the combined forces of the concentration gradient and the electrical gradient are balanced, even if on their own they do not appear to be balanced

Question 9

Two things are required to make an ionic gradient

Answer 9

a selectively permeable membrane and a Na/K ATPase

Question 10

Lipophilic–Hydrophilic Polar–Non polar: which of the three can passively diffuse across a membrane?

Answer 10

the lipophilic and the nonpolar

Question 11

Na+ =

Answer 11

low permeability

Question 12

K+ =

Answer 12

higher permeability at rest (100X of sodium)

Question 13

Ca++

Answer 13

low permeability at ret

Question 14

Cl-

Answer 14

moderate permeability at rest

Question 15

intracellular proteins have what kind of charge?

Answer 15

negative

Question 16

proteins create a

Answer 16

electrical gradient because they are negatively charges

Question 17

negative ions outside the cell are

Answer 17

repelled because of the net negative charge inside the cell, so positive charges are attracted

Question 18

What are the TWO ways a selective permeability helps create the membrane potential

Answer 18

1) by keeping the proteins (with their negative charges) in the cell
2) by not allowing certain ions (e.g. sodium) to enter the cell

Question 19

the Na/K ATPase pumps out more

Answer 19

+ from than into the cell (3Na out, 2K in)

Question 20

what is the Na/K ATPase described as?

Answer 20

electrogenic

Question 21

Sodium is higher

Answer 21

outside the cell than inside

Question 22

Potassium is higher

Answer 22

inside the cell than outside

Question 23

Chloride is higher

Answer 23

outside the cell than inside

Question 24

Calcium is higher

Answer 24

outside the cell than inside

Question 25

electrogenic means the cell

Answer 25

pumps out more (+) than (-)

Question 26

the most important role of the Na/K ATPase is

Answer 26

producing a concentration gradient

Question 27

what happens if you poison the Na/K pump?

Answer 27

the cell depolarizes immediately because of the loss of electrogenic effect of the ATPase, then more slowelr because the concentration gradient begins to equalize

Question 28

how much voltage in a neuron is lost if you poison the Na/K pump?

Answer 28

around 5 mV

Question 29

what is a chemical expression of electrogenicity?

Answer 29

3Na/2K

Question 30

Effect on cell if Na/Ka is poisoned: initial and final

Answer 30

cell death

1) initial 5-10 mV
2) slower depolarization to 0

Question 31

Importance of electrogenicity and Na/K in what cells?

Answer 31

neurons, skeletal muscle CRITICAL

other cells types not as critical

Question 32

part 1: proteins do what

Answer 32

attract positive (K) ions to the interior of the cell

Question 33

part 2: Na/K does what

Answer 33

pumps out 3 Na for every 2 K it pumps it takes in

Question 34

part 3: the membrane doesn’t allow ____ to cross the membrane readily

Answer 34

ions

Question 35

Muscle cells have a resting Vm is

Answer 35

-70 mv to -90 mv

Question 36

the electrical and chemical gradient of Na

Answer 36

e: pulls Na into the cell
c: pulls Na into the cell

Question 37

the electrical and chemical gradient of K

Answer 37

e: pulls K into the cell
c: repels K from the cell

Question 38

the electrical and chemical gradient of Cl

Answer 38

e: repels Cl
c: attracts Cl

Question 39

the electrical and chemical gradient of Ca

Answer 39

e: attracts Ca
c: attracts Ca

Question 40

What happens if the Nernst potential is more negative than the membrane potential?

Answer 40

ions will move out of the cell

Question 41

what happens if the nernst potential is less negative than the membrane potential?

Answer 41

ions will move from the outside to the inside

Question 42

what happens if the nernst potential is equivalent to the membrane potential?

Answer 42

nothing moves because the electrical gradient and the chemical gradient are equal in opposite directions

Question 43

At normal conditions, the equilibrium potential is ____ than the membrane potential

Answer 43

less than

Question 44

if Vm is less negative than the equilibrium value, which direction does the gradient go?

Answer 44

out of the cell

Question 45

if the Vm is more negative than the equilibrium value, which direction does the gradient go?

Answer 45

into the cell

Question 46

V (DF) = Vm - Veq

Answer 46

DF is driving force

driving force = membrane potential minus nernst (equilibrium potential)

Question 47

results of Vm larger than Veq?

Answer 47

cation OUTWARD flow; anion inward flow

Ved is positive

Question 48

result when Vm is smaller than Veq?

Answer 48

cation inward flow, anion outward flow

Ved is negative

Question 49

Vm = Veq ?

Answer 49

no net flow in either direction

Question 50

What happens when the depolarization voltage nears V(Na) ?

Answer 50

The potassium channels are activated

Question 51

Does the V(Na) ever get achieved?

Answer 51

no, just below it

Question 52

What happens when hyperpolarization voltage nears V(k)?

Answer 52

V begins to depolarize slightly until it arrives at Vrest (Vm)

Question 53

Does hyperpolarization ever reach Vk?

Answer 53

no

Question 54

Hey now

Answer 54

Does this work?