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wrote...
11 years ago
I am looking for answers to the Review Sheet portion of Exercise 3: Neurophysiology of Nerve Impulses.  In the lab book these questions start on page PEx-53 and end on page Pex-58. 

The first question:
Q:Explain why increasing extracellular k+ reduces the net diffusion of k+ out of the neuron through the k+ leak channels.
A: Increasing the extracellular potassium reduces the steepness of the concentration gradient and so less potassium diffuses out of the neuron.

I have that answer but I am looking to double check the rest of my answers.  Has anyone completed the entire review?

Thanks for your time!
Aubrey
wrote...
11 years ago
Physiolab 9.0 Exercise 3 answers!
wrote...
11 years ago
I just posted this in my own thread, but here it is again Hope it helps someone:

My prof just graded this exercise for us and posted the answer key. I got an A with the answers I posted above, but here are the "official" ones:  Grinning Face

PhysioEx 3 answer key
Review Sheet
Exercise 3
Neurophysiology of Nerve Impulses

 
Eliciting (Generating) a Nerve Impulse
1. Why don’t the terms depolarization and action potential mean the same thing?
 Depolarization may only be a short lived event if the change in membrane is sub-threshold (local potential0. When an action potential occurs, there is a large reversal of membrane polarity when membrane reaches threshold. This wave is self=propagating.
 
2. What was the threshold voltage in Activity 1?  3 volts
 
3. What was the effect of increasing the voltage? How does this change correlate to changes in the nerve?
Increasing voltage results in depolarization of increasing numbers of neurons in the nerve.
 
4. How did the action potential generated with the unheated rod compare to the that generated with the heated rod?
Action potential generated with the unheated rod was less than the heated one.
 
5. Describe the types of stimuli that generated an action potential.
Electrical, mechanical, thermal, and chemical are all able to generate action potential
 
6. If you were to spend a lot of time studying nerve physiology in the laboratory, what type of stimulus would you use and why?
Although many types of stimuli can be used, electrical stimuli are more convenient because their duration and frequency can be precisely controlled.
 
 
7. Why does the addition of sodium chloride elicit an action potential? Hint: Think about the sodium permeability of the neuron (Figure 3.2e).
By adding sodium chloride, a more than normal amount of sodium will diffuse into the neuron causing membrane potential to reach threshold thus initiating depolarization
 
 
 
Inhibiting a Nerve Impulse
8. What was the effect of ether on eliciting an action potential?
Ether narcotizes the the nerve fiber thus blocking the generation of an action potential 
 
9. Does the addition of ether to the nerve cause any permanent alteration in neural response?
No, the ether has no lasting effect.
 
10. What was the effect of curare on eliciting an action potential?
Curare had no effect on the ability to generate action potential
 
 
11. Explain the reason for your answer to question 10 above.
Curare blocks synaptic transmission which will result in paralysis of the nervous system. Neurons can depolarize but cannot transmit to or stimulate other neurons.
 
12. What was the effect of lidocaine on eliciting an action potential?
Lidocaine blocks sodium channels. Thus preventing the generation of the action potential 
 
Nerve Conduction Velocity
13. What is the relationship between size of the nerve and conduction velocity?
The larger the nerve , the faster the conduction velocity
 
 
 
14. Keeping your answer to question 13 in mind, how might you draw an analogy between the nerves in the human body and electrical wires?
The larger the wire the faster the electrons can flow. Smaller diametr wires offer higher resistance.   
 
15. How does myelination affect nerve conduction velocity? Explain, using your data from Chart 1.
Myelination greatly speeds conduction velocity. Myelinated fiber display salutatory conduction, which is much faster than unmyelinated fiber conduction
 
 
 
16. If any of the nerves used were reversed in their placement on the stimulating and recording electrodes, would any differences be seen in conduction velocity? Explain.
No. once the membrane is depolarized it spreads in a wave like manner. Reversing the nerve would have no effect on conduction velocity.
wrote...
11 years ago
Thanks for this
wrote...
11 years ago
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