Resting Cell Membrane

Question 1

What is a membrane potential?

Answer 1

The electrical potential difference across the plasma membrane of a cell

Question 2

How is a membrane potential measured?

Answer 2

• Using a voltmeter
• Microelectrode penetrates the cell membrane
• Filled with a conducting solution (KCl)

Question 3

How is resting membrane potential measured?

Answer 3

The potential inside the cell relative to the extracellular solution

Question 4

What is the unit of measurement for membrane potential?

Answer 4

millivolts (mV)

Question 5

What is the resting membrane potential of cardiac myocytes and neurones?

Answer 5

Cardiac Myocytes = -80mV

Neurones = -70mV

Question 6

What is the resting membrane potential of skeletal and smooth muscle myocytes?

Answer 6

Skeletal = -90mV
Smooth = -50mV

Question 7

Which ionic channel dominates membrane ionic permeability at rest?

Answer 7

Potassium channels

Question 8

What types of gradients allow movement of K+ ions in and out of the cell?

Answer 8

• K+ moves out of the cell down a chemical (diffusion) gradient
• K+ moves into the cell via an electrical gradient

Question 9

Is there a negative or positive membrane potential when K+ is at equilibrium?

Answer 9

Negative

Question 10

What is the equilibrium potential?

Answer 10

The membrane potential at which K+ is in equilibrium

Question 11

What equation is used to measure the equilibrium potential?

Answer 11

The Nernst equation

Question 12

How do Na+ and Ca2+ channels affect K+ equilibrium potential?

Answer 12

The channels can leak which cancels out some of the negative potential (depolarises)

Question 13

How to Cl- channels and ions contribute to membrane potentials?

Answer 13

• Settles more to equilibrium potential

- Inhibitory to electrical events