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PhysioEx 9.0 Review Sheet 3 Exercise 18B - Neurophysiology
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monroe025
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For a more comfortable homework help experience, try HomeworkClinic.com.
Hope this helps someone.

PhysioEX Exercise 18B: Neurophysiology of Nerve Impulses - Computer Simulation
1.   Why don’t the terms depolarization and action potential mean the same thing?
A depolarization is any change in a neuron that makes it more positive than resting potential, but an action potential only occurs when the depolarization reaches the threshold level.
2.   What was the threshold voltage in Activity 1?
3.0 V
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 a nerve.
4.   How did the action potential generated with the unheated rod compare to that generated with the heated rod?
The action potential generated with the unheated rod was less than the action potential generated by the heated rod.
5.   Describe the types of stimuli that generated an action potential.
Electrical, mechanical, thermal, and chemical stimuli are all capable of generating an 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 different stimuli work, electrical stimulators are convenient because the voltage duration and frequency of the shock can be very precisely set for use.
7.   Why does the addition of sodium chloride elicit an action potential? Hint: Think about the sodium permeability of the neuron (Figure 3.2e).
While the sodium-potassium pump is pumping sodium out of the cell and potassium into the cell, these ions are leaking back where they came from by diffusion. By adding sodium chloride, a more-than-normal amount of sodium will diffuse into the nerve, causing the resting membrane potential to reach the threshold value, bringing about a membrane depolarization.
8.   What was the effect of ether on eliciting an action potential?
There was no effect it conducted the same
9.   Does the addition of ether to the nerve cause any permanent alteration in neural response?
No, the ether has no lasting effect.
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11.   What was the effect of curare on eliciting an action potential?
Curare had no effect - an action potential
12.   Explain the reason for your answer to question 10 above.
Curare stops Acetylcholine. It creates a depolarisation block. Disinhibition from blocking interneurons that express nicotinic accetylcholine receptors.
13.   What was the effect of lidocaine on eliciting an action potential?
Lidocaine is an antagonist inhibitor that blocks sodium ion channels, when these are blocked there's no action potential (nerve impulses).
14.   What is the relationship between size of the nerve and conduction velocity?
A larger nerve will have a faster conduction velocity.
15.   Keeping your answer to question 13 in mind, how might you draw an analogy between the nerves in the human body and electrical wires?
Larger electrical wire has less resistance to current flow and will conduct faster than smaller wire with increased resistance to current flow.
16.   How does myelination affect nerve conduction velocity? Explain, using your data from Chart 1.
Myelination speeds up nerve conduction velocity by causing the nerve impulse to jump across the cell membrane from one internode to another rather than be conducted across the entire cell membrane.
17.   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 a neural membrane is depolarized and the impulse is being conducted along the neural membrane, which direction is which does not matter. We state that a neural impulse is set up in the neuron’s trigger zone (mainly due to the large number of sodium channels there) but once the depolarization is set up, it not only travels down the axon but also around the soma of the cell.


Extra informationPhysio Ex 9.0 Computer Simulation
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Reply# 1
jayjay1
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3 years ago

Please, one post per thread, follow the rules man!



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3 years ago

Please, one post per thread, follow the rules man!

Excuse me? What are you talking about?



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Reply# 3
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3 years ago

Please, one post per thread, follow the rules man!

Those are the answers budd...

@monroe025: Guy's on dope Wink



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Reply# 4
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3 years ago

Too Funny I was so confused



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Reply# 5
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3 years ago

Too Funny I was so confused

Thanks for the contribution, +1.



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Reply# 6
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3 years ago

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:  Grin

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.



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