Lecture 3: Membrane Potentials and Action Potentials

Question 1

What is the Nernst Equation?

Answer 1

EMF = z(61.5) x log ([ion ouside]/[ion inside])
Determines the diffusion potential across a membrane that exactly opposes the net diffusion of a particular ion through the membrane.

Question 2

Why do action potentials typically travel in the orthodromic direction?

Answer 2

This is due to the refractory period and repolarization. An action potential would not typically go in the “backward” direction due to the amount of time it would take for gated channels to return to “closed” state.

Question 3

Why does myelination increase velocity of nerve transmission?

Answer 3

There is less internal resistance at junctions, so action potential is able to participate in saltatory conduction which speeds up transmission.

Question 4

Why do larger diameter fibers conduct action potentials faster than smaller diameter fibers?

Answer 4

There is less internal resistance inside larger fibers and more room for ion current to freely flow.

Question 5

Which of the following types of neurons would transmit an action potential the fastest?

A. Small diameter, non-myelinated
B. Small diameter, myelinated
C. Large diameter, myelinated
D. Large diameter, non-myelinated

Answer 5

C. Large diameter, myelinated

Question 6

Saltatory conduction is a characteristic of which part of a typical neuron?

A. Dendrite
B. Nerve cell body
C. Axon hillock
D. Axon

Answer 6

D. Axon

Question 7

A selectivity filter with carbonyl oxygens is associated with which of the following kinds of ion channels?

A. Gated sodium
B. Non-gated sodium
C. Potassium
D. Chloride

Answer 7

C. Potassium

Question 8

The resting potential for a typical neuron, such as a motor neuron, is best represented by which of the following potentials?

A. 74 mV
B. -74 mV
C. 90 mV
D. -90 mV

Answer 8

D. -90 mV