Module 6.2 - Voltage clamp technique and squid giant axon

Question 1

Who developed the squid giant axon prep?

Answer 1

JZ Young

Question 2

Who invented the voltage clamp technique?

Answer 2

Kenneth Cole

Question 3

What is the significance of the voltage clamp technique?

Answer 3

Allows one to hold and change Vm to different levels during electrophysiological experiments.

Question 4

What was an early realization of electrophysiologists in understanding the AP?

Answer 4

Understanding AP required understanding how GNa and GK change during the course of the AP.

Question 5

What are GNa and GK composed of at rest?

Answer 5

Leak channels

Question 6

What happens to GK and GNa when Vm is depolarized?

Answer 6

Depolarization opens voltage-gated Na and K channels, contributing to GNa and GK.

Question 7

What is the problem with the constant change in Vm during an AP and how does the voltage clamp technique relate?

Answer 7

Constant changes in Vm during an AP result in changes to the conductance of voltage-gated ion channels that contribute to GNa and GK.
Before voltage-clamp, it was not possible to study and understand the properties of NaV and KV channels at different fixed voltages

Question 8

What did Hodgkin and Huxley observe in their first voltage-clamp recordings? (3)

Answer 8

1. A capacitive current
2. An early current
3. A late current