Review Sheet Exercise 3: Neurophysiology of Nerve Impulses

Electrical, mechanical, thermal, and chemical stimuli are all capable of generating an action potential.

Please contribute to the forum if you want me to answer the rest.

how about this?  ill post the rest of the answers i have to aid others working on the same assignment and if you would like correct any mistakes i have made.
*= ones i dont have answers to.


Eliciting (Generating) a Nerve Impulse
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?
There was a slight increase

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.

Inhibiting a Nerve Impulse
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.

10.    *What was the effect of curare on eliciting an action potential?


11.    *Explain the reason for your answer to question 10 above.
   

12.    *What was the effect of lidocaine on eliciting an action potential?

Nerve Conduction Velocity
13.    What is the relationship between size of the nerve and conduction velocity?
A larger nerve will have a faster 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?
Larger electrical wire has less resistance to current flow and will conduct faster than smaller wire with increased resistance to current flow.

 15.    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.

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 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.

Curare works by blocking synaptic transmissions so that neural impulses do not travel from neuron to neuron. The detached nerve which we are experimenting with does not have any synapses to be blocked. In a living animal, however, curare will kill, as neural impulses cannot jump synapses to allow the heart to work or the animal to breathe.

thank you to everyone for the help ... still one unanswered

10. There is no effect.

 12. It blocks sodium ion channels from opening, inhibiting action potentials.

Thanks everybody. I so appreciate your help as well.

10.   What was the effect of curare on eliciting an action potential?
It inhabits action potential because curare is a toxin.

11.   Explain the reason for your answer above.
Because it is a toxin.

12.   What was the effect of lidocaine on eliciting an action potential?
There is no action potential when blocked.

Thank You everyone for your help as well!!   

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

Let us know if you need clarification with the other questions, we can always double check for you!

Can somebody answer those questions for me please im having a hard time with it.. thanks

ACTIVITY9

56.   Describe what happened when you applied a very weak stimulus to the sensory receptor, i.e. was there an action potential?  How many vesicles were released?
57.   Describe what happened when you applied a moderate stimulus to the sensory receptor, i.e. was there an action potential?  How many vesicles were released?
58.   Identify the type of membrane potential (graded receptor potential or action potential) that occurred at R1, R2, R3, and R4 when you applied a moderate stimulus.  (Compare/view the response to the stimulus.)
59.   Describe what happened when you applied a strong stimulus to the sensory receptor.  What type(s) of membrane potential were caused?  Were the responses at R1 through R4 all the same?

Please start a new topic.