Physio Ex 8.0 exercise 3

I can assist you. What question are you stuck on?

activities 6,7, and 8

Activity 6

2. There is no change to the action potential tracing. Nerve propagation is unaffected because curare works on the synaptic ends of the nerve. Curare would ultimately kill the organism by blocking nerve transmission.

Activity 7

1. No.

2. At threshold voltage, the screen still displays a flat line. Lidocaine is a sodium ion channel antagonist which will block sodium channels from opening, thus inhibiting any action potential from being generated.

Exercise 3:  Neurophysiology of Nerve Impulses Worksheet
Assignment Due:  Week 4

Student instructions:  Follow the step-by-step instructions for this exercise found in your text and record your answers in the spaces below.  Submit this completed document by the assignment due date found in the Syllabus.

Please make sure that your answers are typed in RED.

Please type your Nicholle Koppenhaver and 4186699 here:

Eliciting a Nerve Impulse
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? There was a slight increase in voltage results in a light increase in the height of the action potential peak. At threshold voltage, the smaller fibers in a nerve are stimulated and an action potential is seen.
4.   What reason can you give for the change? Increasing the voltage will cause most, if not all of the neural fibers to undergo depolarization. A given nerve is made up of literally thousands of neuron processes (axons) so this slight increase is noted when all fibers in the nerve fire. 
5.   Record this maximal voltage here:     4.0   V

Activity 2:  Mechanical Stimulation

1.   When the glass rod is touching the nerve, what do you see on the oscilloscope screen? An action potential is generated when you touch the rod to the nerve.
2.   How does this tracing compare with the other tracings you have generated? The tracing is identical to the tracing generated at the threshold voltage.

Activity 3:  Thermal Stimulation

1.   What happens when the heated rod touches the nerve? An action potential is generated when you touch the rod to the nerve. 
2.   How does this trace compare to the trace that was generated with the unheated glass bar? The tracing shows the action potential peaking slightly higher then the peak generated by the unheated rod.
3.   What explanation can you provide for this?  Heat generates action potentials in more of the neurons in a nerve than are generated by touch.

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, the tracing does not differ from the original threshold stimulus tracing.
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, the tracing does not differ from the original threshold stimulus tracing.
5.   To summarize your experimental results, what kinds of stimuli can elicit an action potential? Thermal, glass, cold, hydrochloric acid and sodium chloride.


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

1.   What sort of trace do you see? The screen displays a glat line, indicating no nerve response.
2.   What has happened to the nerve? The nerve has been anesthetized by the ether.
3.   How long does it take for the nerve to return to normal? About 6 minutes.

Activity 6:  Testing the Effects of Curare

1.   Does this generate an action potential? No
2.   What explains this effect? Nerve propagation is unaffected because curare works on the synaptic ends of the nerve.
3.   What do you think would be the overall effect of Curare on the organism? Curare would end up killing the organism by blocking nerve transmission.

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? The screen displays a flat line.
3.   Why does Lidocaine have this effect on nerve fiber transmission? Lidocaine is a sodium ion channel antagonist, which will block sodium channels from opening, inhibiting any action potential from being generated.

Nerve Conduction Velocity
Activity 8:  Measuring Nerve Conduction Velocity

1.   Which nerve in the group has the slowest conduction velocity? Earthworm
2.   What was the speed of the nerve? 8.85 m/sec
3.   Which nerve of the four has the fastest conduction velocity? Rat Nerve 2
4.   What was the speed of the nerve? 46.74 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, the faster the conduction elocity. Conduction velocity is faster if the nerve is myelinated than if it is not.
What about size of the neuron/axon? Larger diameter axons lose less charge to “leakage” of potassium and chloride ions through ungated channels, and they provide less resistance to the flow of local current much like an electrical wire; therefore, adjacent regions of the axon membrane are brought to threshold more rapidly
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? In myelinated nerves, conduction velocity is faster as the action potential jumps from node of Ranvier (internode) to node of Ranvier and does not travel along the cell membrane.
7.   What are the evolutionary advantages achieved by the myelination of neurons?  Attack and escape. Myelinated neurons allow faster reflexes increasing chance of survival, which allows you to pass your genes on to your offspring.


hope this helps. I just did it and got an A.

THANK YOU SOOOO MUCH THIS HELPED A TON!!! ON THE REVIEW SHEET SECTION I NEED HELP WITH A COUPLE OTHERS... #3,4,6,15,&17 IF ANYONE CAN HELP I WOULD APPRECIATE IT.

Let me know exercise it is i havent done any reviews sheets.

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