Neurobiology, BI 378

Frog Sciatic Nerve Physiology

I. Instructions:

• Review your notes on the action potential

 

II. On Netscape,

A) Go to:

www.plymouth.edu/biology/

Click on:

• Interactive Animal Physiology Manual then

• Membrane Transport Labs then

• Nerve Conduction

 

B) Read Through before lab:

Background

Set-up

Compound Action Potential

* NOTE THAT THE EQUIPMENT THAT YOU WILL USE IS SLIGHTLY DIFFERENT THAN THAT DESCRIBED

 

C) On lab day, Perform the listed experiments

 

DO NOT CRUSH ANT PART OF THE NERVE YET

 

----------------------------Questions - take enough notes to be able to answer these---------

 

1. The Compound Action Potential:

Describe the trace that you observe at this stimulation level in one sentence.

2. Conduction Velocity

a. Record your raw data and calculate the conduction velocity of your nerve (please show your work).

b. Do you suppose the temperature of the room had any effect on conduction velocity? Explain why or why not.

c. Did you notice any change in the shape of the peak? Describe. What is the basis for this?

3. Strength-Duration Property of the Nerve:

Stimulus - Response Observations:

a. Explain, in a few sentences, why the nerve does not obey the "all or none" principle. Or does it?

b. What happens to the size of the potential above a certain point? Does the potential just keep getting larger? Why or why not?

c. Record your raw data and produce a graph of your data (in the form of a Strength-Duration curve). Be sure to label axes.

d. What physical structure of neurons underlies the strength-duration property of a neuron?

4. Temperature and Conduction Velocity

- What are the effects of temperature and what are the mechanisms for this effect?

5. Bi-directional Conduction

a. Can the nerve conduct action potentials bi-directionally?

b. Does this occur in vivo?

c. Why or why not?

6. Refractory Periods -

Compare your experimental findings on refractory to the theoretical findings that we discussed in class. Any differences? Why or why not? What are the bases for the refractory periods?

 

Assignment: Due next week at the beginning of lab.

• You will each be assigned to present your findings from one of the above questions. You should:

1) Present some of your methodology - enough so that another upper-level biology major can understand what you did.

2) Present your results in the form of one or two figures.

3) Discuss how your results fit (or don't) into our class discussions about the action potential.

 

You will be graded on 1-3 above. Clarity, conciseness and preciseness all count.