[PhysioEX Chapter 3 exercise 7] PEX-03-07

Solved by ramonistry

Exercise 3: Neurophysiology of Nerve Impulses: Activity 7: The Action Potential: Conduction Velocity Lab Report
Pre-lab Quiz Results
You scored 100% by answering 5 out of 5 questions correctly.

1. An action potential can be propagated along an axon because there are __________ channels in the membrane.
   You correctly answered: d. voltage-gated
2. The units of conduction velocity are
   You correctly answered: d. meters/second.
3. Which of the following will affect axonal conduction velocity?
   You correctly answered: c. both the diameter of the axon and the amount of myelination
4. Which of the following describes an A fiber?
   You correctly answered: a. large diameter, heavily myelinated
5. Which of the following describes a C fiber?
   You correctly answered: c. small diameter, unmyelinated

Experiment Results
Predict Question:
Predict Question 1: How will the conduction velocity in the B fiber compare with that in the A Fiber?
Your answer : b. The conduction velocity in the B fiber will be slower because the B fiber has a smaller diameter and less
myelination.
Predict Question 2: How will the conduction velocity in the C fiber compare with that in the B Fiber?
Your answer : b. The conduction velocity in the C fiber will be slower because the C fiber has a smaller diameter and less
myelination.
Stop & Think Questions:

1. Note the difference in time between the action potential recorded at R1 and the action potential recorded at R2. The
   distance between these sets of recording electrodes is 10 centimeters (0.1 m).
   Convert the time from milliseconds to seconds, enter the time (in seconds) in the field below, and then click Submit to
   display your results in the grid.
   You answered: 0.002 sec
2. Calculate the conduction velocity in meters/second by dividing the distance between R1 and R2 (0.1 m) by the time it took
   for the action potential to travel from R1 to R2.
   Enter the conduction velocity in the field below and then click Submit to display your results in the grid.
   You answered: 50 m/sec
3. Note the difference in time between the action potential recorded at R1 and the action potential recorded at R2.
   Convert the time from milliseconds to seconds, enter the time (in seconds) in the field below, and then click Submit to
   display your results in the grid.
   You answered: 0.01 sec
4. Calculate the conduction velocity in meters/second by dividing the distance between R1 and R2 (0.1 m) by the time it took
   for the action potential to travel from R1 to R2.
   Enter the conduction velocity in the field below and then click Submit to display your results in the grid.
   You answered: 10 m/sec
5. Note the difference in time between the action potential recorded at R1 and the action potential recorded at R2.
   Convert the time from milliseconds to seconds, enter the time (in seconds) in the field below, and then click Submit to
   display your results in the grid.
   You answered: 0.1 sec
6. Calculate the conduction velocity in meters/second by dividing the distance between R1 and R2 (0.1 m) by the time it
   took for the action potential to travel from R1 to R2.
   Enter the conduction velocity in the field below and then click Submit to display your results in the grid.
   You answered: 1 m/sec

Experiment Data:
Axon Type Myelination Stimulus
Voltage (mV)
Distance From
R1 to R2 (m)
Time Between
APs (msec)
Time Between
APs (sec)
Conduction
Velocity (m/sec)
A fiber Heavy 30 0.1 2 0.002 50
B fiber Light 30 0.1 10 0.01 10
C fiber None 30 0.1 100 0.1 1

Post-lab Quiz Results
You scored 100% by answering 4 out of 4 questions correctly.

1. Action potential conduction velocity is fastest in which of the following fibers?
   You correctly answered: a. A fibers
2. Action potential conduction velocity is slowest in which of the following fibers?
   You correctly answered: c. C fibers
3. Why did the timescale have to be changed to measure the conduction velocity of the C fibers?
   You correctly answered: b. The total time shown on the oscilloscope would have been too short to see the action potential at
   R2.
4. The axons from touch fibers are A fibers, and the axons from pain fibers are C fibers. When you stub your toe, which
   would you expect to perceive first?
   You correctly answered: b. your toe touching something

Review Sheet Results

1. How did the conduction velocity in the B fiber compare with that in the A Fiber? How well did the results compare with
   your prediction?
   Your answer:
   B fibers have a smaller radius and less myelin than A fibers so the velocity is slower than velocity of A fibers as predicted.
2. How did the conduction velocity in the C fiber compare with that in the B Fiber? How well did the results compare with
   your prediction?
   Your answer:
   The velocity in the C fiber is faster than velocity of B fibers as I predicted
3. What is the effect of axon diameter on conduction velocity?
   Your answer:
   The smaller the axon diameter makes in conduction velocities slower.
4. What is the effect of the amount of myelination on conduction velocity?
   Your answer:
   A greater layer or amount of myelination makes a faster conduction velocity.
5. Why did the time between the stimulation and the action potential at R1 differ for each axon?
   Your answer:
   because each differed in radius and thickness of myelination.
6. Why did you need to change the timescale on the oscilloscope for each axon?
   Your answer:
   Because, when conduction velocity slowed, a longer time needed to record action potential.