Lecture 11

Question 1

How is resting membrane potential measured?

Answer 1

Using a microelectrode

Value always refers to potential inside cell compared to the extracellular solution

Measured in millivolts

Question 2

What are the resting membrane potentials of various cell types?

Answer 2

Skeletal= -90

Cardiac= -80

Nervous= -70

Smooth muscle- -50

Question 3

How is resting membrane potential set up?

Answer 3

Because membrane semi permeable to potassium.

Chemical gradient out of cell makes inside more negative as losing positive charge.

However if inside becomes too negative electrochemical gradient will overcome chemical gradient and potassium will move back into the call

Question 4

What determines the equilibrium potential for potassium?

Answer 4

The balance between the electrochemical and chemical gradients

Question 5

What equation is used to calculate the equilibrium potential?

Answer 5

The Nernst equation.

Resting membrane potential is a balance between the equilibrium potentials of cellular ions

Question 6

Why is resting membrane potential not the same as Ek?

Answer 6

Leakage of sodium and calcium into cell raises the resting membrane potential