5: Origin of membrane potentials

Question 1

The plasma membranes of all cells are (polarised / depolarised).

Answer 1

polarised

Question 2

What is membrane potential (E_m)?

Answer 2

Separation of opposite charges across the membrane

Question 3

What is the unit of membrane potential?

Answer 3

millivolts (mV)

Question 4

Membrane potential is a measure of the difference in charge between the _CF and _CF.

Answer 4

ECF and ICF

Question 5

What is the name given to a rapid, transient change in membrane potential?

Answer 5

Action potential

Question 6

What is an action potential?

Answer 6

A rapid, transient change in membrane potential

Question 7

Which type of cells can produce action potentials?

Answer 7

Excitable cells such as nerves and muscle

Question 8

Na⁺ is highly concentrated (inside / outside) cells.

Answer 8

inside

Question 9

K⁺ is highly concentrated (inside / outside) cells.

Answer 9

outside

Question 10

Cl^_ is highly concentrated (inside / outside) cells.

Answer 10

outside

Question 11

The Na⁺ concentration gradient is (inward / outward).

Answer 11

inward

Question 12

The K⁺ concentration gradient is (inward / outward).

Answer 12

outward

Question 13

What is the equilibrium potential of an ion?

Answer 13

The membrane potential at which the concentration gradient of the ion equals the electrical gradient in the opposite direction

Question 14

What is the equilibrium potential for K⁺?

Answer 14

-90mV

Question 15

What is the equilibrium potential for Na⁺?

Answer 15

+60mV

Question 16

What is the permeability of K⁺ compared to that of Na⁺?

Answer 16

Around 100x greater

Question 17

What is the permeability of Na^{+<strong> </strong>}compared to that of K⁺?

Answer 17

Around 100x less

Question 18

The greater the ___ of an ion, the greater the tendency of that ion to drive the membrane potential towards its own ___ potential.

Answer 18

permeability , equilibrium potential

Question 19

What is the typical resting membrane potential for a nerve cell?

Answer 19

-70mV

Question 20

Why is the resting membrane potential for a nerve cell around -70mV?

Answer 20

Tends towards E_K+ (-90mV) because K⁺ is 100x more permeable than Na⁺

However, not equal to E_K+ because of inward Na⁺ leak

Question 21

What equation can be used to calculate the equilibrium potential of an ion?

Answer 21

Nernst equation

Question 22

What equation can be used to calculate the membrane potential of a cell?

Answer 22

GHK equation

Question 23

Which integral protein can have an effect on the membrane potential of a cell?

Answer 23

Na^+-K⁺ATPase

(sodium-potassium pump)

Question 24

The sodium-potassium pump generates a

(depolarising / repolarising / hyperpolarising)

current.

Answer 24

hyperpolarising

Question 25

Which types of cells will have fluctuating membrane potentials?

Answer 25

Nerve cells

Muscle cells

as they generate action potentials a lot.

Question 26

Which ion is most important in setting the membrane potential?

Answer 26

K^{+<strong> </strong>}(100x more permeable than sodium)