Membrane potential

Question 1

What is resting membrane potential?

Answer 1

The voltage difference across the cell membrane when the cell is at rest; it establishes a starting point for a cell to be excited

Question 2

What is the ion concentration of potassium outside and inside the cell?

Answer 2

4.5 mM outside and 155 mM inside

Question 3

Removing which ion channel from the plasma membrane of a neuron will have the greatest influence on disrupting resting membrane potential?

Answer 3

Potassium leak channels

Question 4

Which ion channel establishes resting membrane?

Answer 4

Potassium leak channel

Question 5

How many ions of sodium and potassium does the Na/K ATPase exchange?

Answer 5

3 Na+ go out for 2 K+ to come in

Question 6

What is the ratio of potassium leak channels to sodium leak channels?

Answer 6

100:1

Question 7

What is the resting membrane potential for muscle (cardiac/skeletal)?

Answer 7

-80 to -90 my

Question 8

What is the resting membrane potential for smooth muscle?

Answer 8

-60 my

Question 9

What is the resting membrane potential for neurons?

Answer 9

-60 to -70 mv

Question 10

What forces act on ions to develop membrane potential?

Answer 10

Diffusion forces, electrostatic forces and electrochemical forces

Question 11

What are diffusion forces?

Answer 11

Chemical concentration gradients

Question 12

What are electrostatic forces?

Answer 12

Electrical gradients (based on charge, opposites attract)

Question 13

What are Electrochemical forces?

Answer 13

Diffusion forces and electrical forces

Question 14

What is equilibrium potential?

Answer 14

Membrane potential when electrical and chemical forces equally counteract each other, no further movement occurs (does not equal resting membrane potential) (the voltage/charge required to maintain a specific concentration gradient that allows no movement across the membrane, where chemical forces and electrostatic forces cancel each other out)

Question 15

Why does sodium have a positive equilibrium potential? Why does potassium have a negative?

Answer 15

Because there is more sodium outside than inside (150mM vs 15mM), the chemical gradient is directing it to move inside the cell, and so the equilibrium potential must be positive (+66mv) to drive sodium out (because like charges repel)

Because there is more Potassium inside than outside so it requires a negative potential (-91 mv) inside to stop movement of potassium going out. (Positive potassium ions will be attracted to the negative charge inside)

Question 16

Why do sodium and potassium ions have equilibrium potentials not near resting membrane potential?

Answer 16

Because the sodium potassium ATPase keeps sodium and potassium out of equilibrium in resting neurons; this resting membrane potential is necessary for action potential

Question 17

Which ion does have an equilibrium potential near resting potential?

Answer 17

Chloride

Question 18

What is the nerve equation?

Answer 18

Equilibrium of an ion = (61.5/z)*Log([x]out/[x]in)

Used to calculate equilibrium potential

Question 19

What his the driving force? And the equation?

Answer 19

The driving force takes into account electrical and chemical forces to predict movement of ions

It is the resting membrane potential - equilibrium potential

A positive driving force will represent efflux while a negative will represent influx

Question 20

What are the equilibrium potentials of K, Na, Ca, and Cl?

Answer 20

-91

+61.5

+123

-66.4

Question 21

What are the estimates for directionality?

Answer 21

Ion in > ion out = log will be negative

Ion in < ion out = log will be positive

Ion in = ion out = log will be zero

Question 22

Which ions are more permeable and which ones are less?

Answer 22

Potassium is highly permeable (80-86%) while sodium, calcium and chloride are not that permeable

Question 23

Why does sodium have minimal contribution to the resting membrane potential?

Answer 23

Because of its low permeability

Question 24

What is the contribution of the sodium potassium atp pump to the resting membrane potential?

Answer 24

4mv (minimal)

Question 25

How does a positive or negative resting membrane potential influence depolarization?

Answer 25

A more positive RMP will make it easier to depolarize the cell whereas a more negative RMP will make it more difficult (further away from threshold)

Question 26

What is repolarization?

Answer 26

When the membrane potential is returning towards resting membrane potential?

Question 27

What are the key properties of action potentials?

Answer 27

All or none

Propagating or self-reinforcing

Non-decremental

Question 28

What is a graded potential?

Answer 28

Change in membrane potential that is small and local (excitatory or inhibitory) they dissipate with distance because potassium leak channels are always open

Question 29

How does the strength of initial graded potential correlate with the strength of triggering an event?

Answer 29

Strong triggering event will cause more channels to open and change polarity of a membrane

Question 30

What phase of an action potential is resting?

Answer 30

Phase 4

Question 31

What phase of an action potential is depolarization?

Answer 31

Phase 0

Question 32

What phase of an action potential is repolarization?

Answer 32

Phase 3

Question 33

What phase of an action potential is hyperpolarization?

Answer 33

It’s the refractory period

Question 34

What is overshoot?

Answer 34

When the membrane potential is above 0