Question

In an experiment to measure the speed of conduction of a nerve impulse along a giant axon, the distance between the stimulating and recording electrodes was varied and the delay between stimulus and response was recorded for each distance. The results are shown in the graph below:


From these results the mean speed of conduction was found to be

• A. $2.0{\text{m s}}^{–1}$
• B. $2.5{\text{m s}}^{–1}$
• C. $0.5{\text{m s}}^{–1}$
• D. $4.0{\text{m s}}^{–1}$

Answer 1

The correct option is D $4.0{\text{m s}}^{–1}$

The conduction velocity of the action potential is determined by measuring the distance travelled (length of the nerve in m) and dividing by the time (sec) taken to complete the reflex arc, also called the latency.
Conduction velocity = distance (m)/time (sec) = distance between the stimulating and recording electrodes/delay time

a) For the first result, conduction velocity $=2\text{cm}/5\text{ms}=0.4\text{cm}/\text{ms}$
b) For second result, conduction velocity $=4\text{cm}/10\text{ms}=0.4\text{cm}/\text{ms}$
c) For third result, conduction velocity $=6\text{cm}/15\text{ms}=0.4\text{cm}/\text{ms}$
d) For fourth result, conduction velocity $=8\text{cm}/20\text{ms}=0.4\text{cm}/\text{ms}$

That means mean speed of conduction $=0.4\text{cm}/\text{ms}$ = 4 m/s.