Lecture 3: Resting Membrane Potential

Question 1

How membrane potential is measured (units)

Answer 1

Millivolts

Question 2

What allows membrane potential to do its work

Answer 2

Separation of opposite charges across membrane

Question 3

What causes membrane potential

Answer 3

Differences in concentration and permeability of key ions

Question 4

Charge of the inside of the cell

Answer 4

Negative

Question 5

Charge of the outside of the cell

Answer 5

Positive

Question 6

Where are separated charges arranged

Answer 6

Near cell membrane

Question 7

Magnitude of membrane potential is proportional to

Answer 7

Number of charges

Question 8

Ion channels: definition

Answer 8

Polypeptide chains that form water filled pores

Question 9

Are ion channels selective

Answer 9

Yes

Question 10

4 types of ion channels

Answer 10

-carrier
-undated
-ligand gated
-voltage gated

Question 11

In the absence of a stimulus, ion channels can be

Answer 11

Ungated or leaky

Question 12

Carrier ion channel: how it works

Answer 12

-Material carried by transport protein that binds tightly to material
-complex moves through lipid bilayer

Question 13

Ungated channel: how it works

Answer 13

-allow certain ion to leak through pore

Question 14

Ligand gated ion channel: how it works

Answer 14

-transport protein forms pore through membrane
-access to pore is controlled by gate
-opening and closing of gate is controlled by binding of ligand to channel

Question 15

Voltage gated channels: how it works

Answer 15

-opening and closing of gate controlled by electrical field around channel

Question 16

2 types of driving forces for diffusion of ions through open channel

Answer 16

-chemical
-electrical

Question 17

What causes electrochemical gradient

Answer 17

Combination of chemical and electrical forces

Question 18

Is diffusion of ion through an open channel a passive or active process

Answer 18

Passive

Question 19

What will happen in a cell where membrane is permeable to K+ but not Cl- (3)

Answer 19

-Cl remains in cytosol but K+ diffuses across membrane inside cell
-will get greater negative charge inside cell
-influx of K+ containers until electrochemical equilibrium for K+ is reached

Question 20

Equilibrium potential for single ion: definition

Answer 20

Diffusion potential that exactly balances or opposes the tendency for diffusion of an ion down its concentration gradient

Question 21

When is an ion in equilibrium

Answer 21

When chemical and electrical driving forces are equal and opposite

Question 22

Which ion is the most permeable

Answer 22

K+

Question 23

What is the Nernst equation used for

Answer 23

Calculate equilibrium potential for an ion at a given concentration difference across membrane

Question 24

What is one assumption of Nernst equation

Answer 24

Membrane is permeable to ion

Question 25

What does Nernst equation determine

Answer 25

Electrical force required to just balance a given diffusion force

Question 26

Nernst equation: alphanumeric

Answer 26

Eion = (60/z)log([ion]out / [ion]in)

Question 27

Nernst equation: meaning of symbols

Answer 27

Eion = equilibrium potential for ion (mV) Z = ionic valence for ion [ion]out = extracellular concentration for ion [ion]in = intracellular concentration for ion

Question 28

What causes an ion to have 0 membrane potential

Answer 28

No permeability

Question 29

Which ion has the greatest influence on resting membrane potential and why (Na+ vs K+)

Answer 29

K+ because of leaky ion channels (highest permeability)

Question 30

Ohm’s law aka

Answer 30

Goldman equation

Question 31

What does ohm’s law/Goldman equation estimate

Answer 31

Membrane potential knowing the equilibrium potential and conductive for each ionic species in question

Question 32

2 main symbols in ohm’s law/Goldman equation

Answer 32

G = conductance E = equilibrium potential

Question 33

Ohm’s law/Goldman equation: alpha numeric

Answer 33

Em = (g of ion x E of ion) + (g of ion x E of ion) + … / (g of ion + g of ion + …)

Question 34

Ohm’s law/Goldman equation: symbols explained

Answer 34

Membrane potential = sum of (conductance x equilibrium potential for each ion) divided by total conductance

Question 35

Simplified version of resting membrane potential equation/ohm’s law (Since we focus on Na+ and K+)

Answer 35

‘Em = (gKEK + gNaENa) / (gK + gNa)

Question 36

Hyperpolarization

Answer 36

-when membrane potential becomes more negative or closer to equilibrium potential of ion

Question 37

Hypokalemia definition

Answer 37

Decreased potassium in ECF

Question 38

Hypokalemia: clinical correlation with resting membrane potential

Answer 38

-leads to hyper polarized RMP -muscle cells can’t contract properly -leads to paralysis, diaphragmatic suffocation, asystole

Question 39

Role of sodium potassium pump on membrane potential

Answer 39

Maintain ion gradient

Question 40

Na/K pump: Membrane potential is caused by

Answer 40

Diffusion of K+ and Na+ down concentration gradients through ion channels

Question 41

Increased ECF K+ called

Answer 41

Hyperkalemia

Question 42

Hyperkalemia leads to (depolarization or hyperpolarization)

Answer 42

Depolarization

Question 43

Hyponatremia definition

Answer 43

Decreased ECF Na+

Question 44

Hyponatremia leads to (hyperpolarization or depolarization)

Answer 44

Hyperpolarization

Question 45

Hypernatremia leads to (hyperpolarization or depolarization)

Answer 45

Depolarization