Membrane Potential

Question 1

What is the membrane potential of a cell? What is it measured in?

Answer 1

The magnitude of an electrical charge that exists across a plasma membrane?

Millivolts

Question 2

Which type of cell has the lowest resting membrane potential?

Answer 2

Erythrocytes (-9mV)

Question 3

How do you measure a membrane potential?

Answer 3

Two electrodes connected to a voltmeter
One electrode = microelectrode
Filled with conducting solution
Penetrates the plasma membrane?

Question 4

What is a microelectrode? What is the diameter of its tip?

Answer 4

Fine glass pipette used to penetrate the plasma membrane to measure membrane potentials

1 micrometre

Question 5

What type of channels dominate the membrane of a resting cell?

Answer 5

Open K+ channels

Question 6

What does the equilibrium potential of an ion measure?

Answer 6

The voltage at which the electrical gradient and chemical gradient of an ion balance

Question 7

What factors affect the resting membrane potential of a cell?

Answer 7

Permeability of the cells to each particular ion (e.g. No of channels for each ion)

Question 8

What is depolarisation?

Answer 8

A decrease in the size of the membrane potential from its original value (e.g. -70mV to -30mV)

Question 9

What is hyperpolarisation?

Answer 9

An increase in the size of the membrane potential over its original value (e.g. -70mV to -90mV)

Question 10

An increase in permeability to an ion will move the membrane potential towards…

Answer 10

The equilibrium potential for that particular ion

Question 11

What is the equilibrium potential for K+?

What is the equilibrium potential for Cl-?

Answer 11

• 95mV

- 96mV

Question 12

What is the equilibrium potential for Na+?

What is the equilibrium potential for Ca2+?

Answer 12

+70mV

+122mV

Question 13

Opening of _______/_______ channels causes depolarisation

Answer 13

Na+ and Ca2+ channels

Question 14

Opening of K+/Cl- channels causes….

Answer 14

Hyperpolarisation

Question 15

What is conductance?

Answer 15

Refers to the fact that the contribution of an ion to the membrane potential will depend on how permeable the membrane is to that ion

Question 16

What ions do nicotinic ACh receptors transport?

Answer 16

Moves both Na+ and K+

Question 17

Where in the body can you find mechanically gated channels?

Answer 17

Hair cells in the inner ear

Question 18

What two types of synaptic transmission exist?

Answer 18

Fast and slow

Question 19

What is fast synaptic transmission?

Answer 19

Where the receptor protein is also the ion channel? (E.g. Nicotinic ACh receptors)

Question 20

At inhibitory synapses channels open that are permeable to…

Answer 20

K+ and Cl-

Question 21

At excitatory synapses channels open that are permeable to…

Answer 21

Na+ and Ca2+

Question 22

What is slow synaptic transmission?

Answer 22

Where the receptor protein and ion channel are separate proteins (e.g. GPCRs)

Question 23

What is the contribution of the Na/K ATPase pump to the membrane potential

Answer 23

Minimal - contributes a few mV

Question 24

What happens in the Beta-cells of the Islets of langerhans in response to increased glucose levels?

Answer 24

Increase ATP
ATP binds to ATP-sensitive K+ channels - closing them
[K+] in the cell increases
Membrane depolarisation
Calcium channels open, Ca into the cell, insulin released

Question 25

What can sulphonylurea be used for?

Answer 25

To permanently close ATP-sensitive K+ channels

Question 26

What specific properties do cardiac ion channels possess?

Answer 26

Each channel will only transport one type of ion

They are all voltage dependent

Question 27

What is the resting potential in cardiomyocytes?

Answer 27

-90mV

Question 28

When do calcium channels open in cardiomyocytes?

Answer 28

-40mV