Physioex 8.0 Exercise 3

Activity 1: Electrical Stimulation

1. Do you see any kind of response on the oscilloscope screen? NO
2. What was the threshold voltage, or the voltage at which you first saw an action potential? 3.0 V
3. How does this tracing compare to the one that was generated at the threshold voltage? The tracing travel in the same fashion but the tracing were different with an increase threshold voltage
4. What reason can you give for the change? Increase voltage
5. Record this maximal voltage here: 6.0 V

Activity 2: Mechanical Stimulation

1. When the glass rod is touching the nerve, what do you see on the oscilloscope screen? The nerve’s action potential to stimuli
2. How does this tracing compare with the other tracings you have generated? They are traced in the same fashion

Activity 3: Thermal Stimulation

1. What happens when the heated rod touches the nerve? Action potential in increased
2. How does this trace compare to the trace that was generated with the unheated glass bar? The tracing were similar but the heat increase the action potential
3. What explanation can you provide for this? The heat stimuli generated a stronger nerve impulse

Activity 4: Chemical Stimulation

1. Does the sodium chloride generate an action potential? Yes
2. Does this tracing differ from the original threshold stimulus tracing? If so, how? No, they are the same.
3. Does the hydrochloric acid generate an action potential? Yes
4. Does this tracing differ from the original threshold stimulus tracing? If so, how? No.
5. To summarize your experimental results, what kinds of stimuli can elicit an action potential? Any stimuli that has a strong enough threshold stimulus such as physical stimulation such as heat or chemical stimulation such as sodium chloride.

Inhibiting a Nerve Impulse
Activity 5: Testing the Effects of Ether

1. What sort of trace do you see? Flat trace
2. What has happened to the nerve? Ether blocked the nerve impulse transmission to another neuron
3. How long does it take for the nerve to return to normal? 6 minutes

Activity 6: Testing the Effects of Curare

1. Does this generate an action potential? Yes
2. What explains this effect? It affects the neurons by giving it an impulse, but blocks the transmission to other neurons at the synapatic cleft.
3. What do you think would be the overall effect of Curare on the organism? It affect the neuromuscular system that will eventually inhibit muscle movement leading the body into paralysis.

Activity 7: Testing the Effects of Lidocaine

1. Does this generate a trace? No
2. What sort of tracing is seen at the threshold voltage? Flat trace
3. Why does Lidocaine have this effect on nerve fiber transmission? It blocks the sodium ions from entering a cell which inhibits the action potential

Nerve Conduction Velocity
Activity 8: Measuring Nerve Conduction Velocity

1. Which nerve in the group has the slowest conduction velocity? Worm
2. What was the speed of the nerve? 8.90 m/sec
3. Which nerve of the four has the fastest conduction velocity? Rat #2
4. What was the speed of the nerve? 50.00 m/sec
5. What is the relationship between nerve size and conduction velocity? What are the physiological reasons for this relationship? The larger the nerve or diameter of the nerve allows conduction to be a lot faster, without too much restriction
6. Based on the results, what is your conclusion regarding the effects of myelination on conduction velocity? What are the physiological reasons for your conclusion? Myelination prevents ions from seeping through the membrane which creates a type of insulation for the axons.
7. What are the evolutionary advantages achieved by the myelination of neurons? The advantages are that faster impulses are sent to other neurons creating a better chance at survival against life’s enemies. Eventually this will be passed on to offspring through genes.