Lecture 7: Resting Membrane Potential

Question 1

What is a membrane potential?

Answer 1

Electrical charge that exists across a membrane, expressed as potential inside the cell relative to the extracellular solution

Question 2

How to measure the resting potential of a cell?

Answer 2

Using a micro electrode to penetrate the cell, voltmeter will show

Question 3

What is the membrane potential in cardiac myocytes?

Answer 3

-80mV

Question 4

What is the membrane potential in neurons?

Answer 4

-70mV

Question 5

What is the membrane potential in skeletal muscle myocytes?

Answer 5

-90mV

Question 6

What is the membrane potential in smooth muscle myocytes?

Answer 6

-50mV

Question 7

What is the concept of selective permeability?

Answer 7

Allowing only certain types of substances to enter cell

Question 8

What are the 3 factors that contribute to the selective permeability of cell membranes?

Answer 8

• Phospholipid bilayer: permeable to small uncharged molecules but very impermeable to ions
• Ion channels: enables ions to cross cell membranes (for specific ions, gated)

Question 9

How is the resting potential set up given the distribution of ions across cell membranes?

Answer 9

• Open K+ channels dominate the membrane ionic permeability at rest
• Chemical gradient is outwards, electrical gradient is inwards
• When chemical gradient and electrical gradient is equal, no net movement of K+ but there is a negative membrane potential
• Resting membrane potential arises because the membrane is selectively permeable to K+

Question 10

What does equilibrium potential for an ion mean?

Answer 10

Electrical and chemical gradients for that ion are equal, so there is no net driving force on that ion across the membrane

Question 11

How do you calculate the value of equilibrium potential for an ion?

Answer 11

Using Nernst equation

E = 61/z x mV x log19 [K] out / [K] in