Lab 3 - Neurophysiology of Nerve Impulses (p. 31)
Introduction:
In this lab, I will investigate what agents elicit or block nerve impulses and learn what conduction velocity and nerve myelination have to do with speed of nerve transmission. I will define Key Terms that describe what will occur in the experiments; I will conduct an experiment for each Activity and provide all resulting Data as well as answer Questions from each Activity. I will then provide a short Summary for what I learned in each Activity.
Key Terms: ?define each key term from lab manual/background materials
Excitability (p. 31) -
Conductivity (p. 31) -
Resting membrane potential (p. 31) -
Polarized (p. 969 Hole's - "polarization") -
Sodium-potassium pump (p. 31) -
Threshold stimulus (p. 32) -
Depolarization (p. 33) -
Threshold (p. 33) -
Action Potential (p. 32) -
Repolarization (p. 33) -
Hyperpolarization (p. 33) -
Absolute refractory period (p. 33) -
Relative refractory period (p. 33) -
Nerve impulse (p. 33) -
Oscilloscope (p. 33) -
Compound Nerve Action Potential (p. 33) -
ELICITING (GENERATING) A NERVE IMPULSE
Activity 1: Electrical Stimulation
Data: ?record all electrical stimulation data here; to make a screen shot, press "PrtScr" at the top of your keyboard and then right click in your template exactly where you want to put your screen shot and click "Paste"
Questions: ?answer each question; ask the instructor if you need help
1-1: Do you see any kind of response on the oscilloscope screen?
1-2: What was the threshold voltage, that is, the voltage at which you first saw an action potential? ______V
1-3: How does this tracing compare to the one trace that was generated at the threshold voltage? (Hint: look very carefully at the tracings.)
1-4: What reason can you give for the change? Increased voltage causes _____________ (more, less, the same amount of - choose one) nerve fibers to depolarize.
1-5: Record this maximal voltage (the point beyond which no further increase occurs in the peak of the action potential) here: ______V
Summary:
In this activity, I learned that: ? write 1-2 sentences on what you observed by doing this experiment – think “big picture”
Activity 2: Mechanical Stimulation
Data: ?record all mechanical stimulation data here
Questions: ?answer each question; ask the instructor if you need help
2-1: What do you see on the oscilloscope screen - is there an action potential?
2-2: How does this tracing compare with the other tracings that you have generated?
Summary:
In this activity, I learned that: ? write 1-2 sentences on what you observed by doing this experiment – think “big picture”
Activity 3: Thermal Stimulation
Data: ?record all thermal stimulation data here
Questions: ?answer each question; ask the instructor if you need help
3-1: What happens - is there an action potential?
3-2: How does this trace compare to the trace that was generated with the unheated glass rod?
3-3: What explanation can you provide for this? Heat generates ______________ (more, less, the same amount of - choose one) action potentials than simple touch.
Summary:
In this activity, I learned that: ? write 1-2 sentences on what you observed by doing this experiment – think “big picture”
Activity 4: Chemical Stimulation
Data: ?record all chemical stimulation data here
Questions: ?answer each question; ask the instructor if you need help
4-1: Does this generate an action potential?
4-2: Does this tracing differ from the original threshold stimulus tracing?
4-3: Does this generate an action potential?
4-4: Does this tracing differ from the one generated by the original threshold stimulus?
4-5: To summarize your experimental results, what kinds of stimuli can elicit an action potential? (Hint: consider the results of your Activity 1,2, 3 AND 4 when you answer this question).
Summary:
In this activity, I learned that: ? write 1-2 sentences on what you observed by doing this experiment – think “big picture”
INHIBITING A NERVE IMPULSE
Activity 5: Testing the Effects of Ether
Data: ?record all ether data here
Questions:
5-1: What sort of trace do you see - is there an action potential?
5-2: What has happened to the nerve?( Hint: consider the effects of ether).
5-3: How long does it take for the nerve to return to normal? _______ minutes
Summary:
In this activity, I learned that: ? write 1-2 sentences on what you observed by doing this experiment – think “big picture”
Activity 6: Testing the Effects of Curare
Data: ?record all curare data here
Questions:
NOTE: Under #2, "Set the voltage at that level, and click Single Stimulus to stimulate the nerve" should read "Set the voltage at that level, and click Stimulate to stimulate the nerve."
6-1: Does this generate an action potential?
6-2: What explains this effect? (Hint: consider where curare works - p. 37).
6-3: What do you think would be the overall effect of curare on the organism? (Hint: consider your experimental results and what might happen if this occurred in all nerves of the organism).
Summary:
In this activity, I learned that: ? write 1-2 sentences on what you observed by doing this experiment – think “big picture”
Activity 7: Testing the Effects of Lidocaine
Data: ?record all lidocaine data here
Questions:
7-1: Does this generate a trace - is there an action potential?
7-2: What sort of tracing is seen - is there an action potential?
7-3: Why does lidocaine have this effect on nerve fiber transmission? (Hint: consider lidocaine's effect on sodium channels - p. 37).
Summary:
In this activity, I learned that: ? write 1-2 sentences on what you observed by doing this experiment – think “big picture”
NERVE CONDUCTION VELOCITY
Activity 8: Measuring Nerve Conduction Velocity
Data:
-fill in Chart 1 with your data
CHART 1:
Nerve: Earthworm Frog Rat Nerve 1 Rat Nerve 2
(S, no myelin) (M, myelin) (M, no myelin) (L, myelin)
Threshold Voltage:
Elapsed Time from
stimulation to
action potential:
Conduction velocity:
Questions:
8-1: At what threshold voltage do you first see an action potential generated? ______V
8-2: Which nerve in the group has the slowest conduction velocity (hint: HIGHEST time - remember that slowest speed equals most or highest time)?
8-3: What was the speed of the nerve?
8-4: Which nerve in the group of four has the fastest conduction velocity (hint: LOWEST time - remember that fastest speed equals least or lowest time)?
8-5: What was the speed of the nerve?
8-6: What is the relationship between nerve size and conduction velocity? Larger nerves have _____________ (faster, slower, the same - choose one) conduction velocity.
8-7: Based on the results, what is your conclusion regarding conduction velocity and whether the nerve is myelinated or not? Myelination ______________(speeds up, slows down, has no effect on - choose one) nerve conduction velocity.
8-8: What is the major reason for the differences seen in conduction velocity between the myelinated nerves and the unmyelinated nerves? (Hint: this has to do with how the action potential moves).
Summary:
In this activity, I learned that: ? write 1-2 sentences on what you observed by doing this experiment – think “big picture”
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