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• Jila Hafizi

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Name: jila hafizi 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

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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: 3. 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 Data to display your results in the grid. You answered: .001 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 Data to display your results in the grid. You answered: 50 m/sec 7. 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 Data to display your results in the grid. You answered: .01 sec 8. 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 Data to display your results in the grid. You answered: 10 m/sec 11. 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 Data to display your results in the grid. You answered: .1 sec 12. 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 Data to display your results in the grid. You answered: 1 m/sec

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Experiment Data: Axon Type

Myelination

A fiber B fiber C fiber

Heavy Light None

Stimulus Voltage (mV) 30 30 30

Distance From R1 to R2 (m) 0.1 0.1 0.1

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Time Between APs (msec) 2 10 100

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Time Between APs (sec) .001 .01 .1

Conduction Velocity (m/sec) 50 10 1

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Post-lab Quiz Results You scored 75% by answering 3 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? Your answer: a. The total time shown on the oscilloscope would have been too long to see the action potential at R2. Correct answer: 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

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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 fiber was slower. My prediction was correct. 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: C fiber was slower. My prediction was correct. 3. What is the effect of axon diameter on conduction velocity? Your answer: the larger the diamater the faster the velocity and the smaller the diamater the slower the veocity 4. What is the effect of the amount of myelination on conduction velocity? Your answer: The more myelination the faster the velocity and less myelination the slower the velocity. 5. Why did the time between the stimulation and the action potential at R1 differ for each axon? Your answer: Fiber A was the fastest so the action potential occured quickly compared to Fiber B and Fiber B was faster than Fiber C. 6. Why did you need to change the timescale on the oscilloscope for each axon? Your answer: We needed a timescale to match the time of the action potential occurence. So for Fiber A which had quick action potential's a small time scale and the same change was needed for B and C

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