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Physio Ex 9.0 Exercise 3 Review Sheet Neurophysiology of Nerve Impulses
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Hey everyone! I'm new to this so hopefully these questions haven't been posted before. I tried looking around for them and couldn't find them so if anyone has seen them, a link would be appreciated. Thank you :-)

My questions are from Physio Ex 9.0 Exercise 3 review sheet (pg 51) Neurophysiology of Nerve Impulses

Activity 1: The Resting Membrane Potential
3. Explain why a change in extracellular Na+ did not alter the membrane potential in the resting neuron.

Activity 2: Receptor Potential
1. Sensory neurons have a resting potential based on the efflux of potassium ions (as demonstrated in Activity 1). What passive channels are likely found in the membrane of the olfactory receptor, in the membrane of the Pacinian corpuscle, and in the membrane of the free nerve ending?

2. What is meant by the term graded potential?

3.Identify which of the stimulus modalities induced the larges amplitude receptor potential in the Pacinian corpuscle. How well did the results compare with your prediction?

4. Identify which of the stimulus modalities induced the largest-amplitude receptor potential in the olfactory receptors. How well did the results compare with your prediction?

5. The olfactory receptor also contains a membrane protein that recognizes isoamyl acetate and, via several other molecules, transduces the odor stimulus into a receptor potential. Does the Pacinian corpuscle likely have the isoamyl acetate receptor protein? Does the free nerve ending likely have this isoamyl acetate receptor protein?

6. What type of sensory neuron would likely respond to a green light?

Activity 3: The Action Potential: Threshold
1. Define the term threshold as it applies to an action potential.

2. What change in membrane potential (depolarization and hyperpolarization) triggers an action potential?

3. How did the action potential at R1 (or R2) change as you increased the stimulus voltage above the threshold voltage? How well did the results compare with your prediction?

4. An action potential is an "all-or-nothing" event. Explain what is meant by this phase.

5. What part of a neuron was investigated in this activity?

Activity 4: The Action Potential: Importance of Voltage-Gated Na+ Channels
1. What does TTX do to voltage-gated Na+ channels?

2. What does lidocaine do to voltage-gated Na+ channels? How does the ffect of lidocaine differ from the effect of TTX?

3. A nerve is a bundle of axons, and some nerves are less sensitive to lidocaine. If a nerve, rather than an axon, had been used in the lidocaine experiment, the responses recorded at R1 and R2 would be the sum of all the action potentials (called a compound action potential). Would the response at R2 after lidocaine application necessarily by zero? Why or why not?

4. Why are fewer action potentials recorded at R2 when TTX is applied between R1 and R2? How well did the results compare with your prediction?

5. Why are fewer action potentials recorded at R2 when lidocaine is applied between R1 and R2? How well did the results compare with your prediction?

6. Pain-sensitive neurons (called nociceptors) conduct action potentials from the skin or teeth to sites in the brain involved in pain perception. Where should a dentist inject the lidocaine to block pain perception?

Extra informationPhysio Ex 9.0
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Physio Ex 9.0 Exercise 3 Review Sheet Neurophysiology of Nerve Impulses
Feb 16, 2012

6. Pain-sensitive neurons (called nociceptors) conduct action potentials from the skin or teeth to sites in the brain involved in pain perception. Where should a dentist inject the lidocaine to block pain perception?

Lidocaine should be applied to the receptors to prevent the generation of an action potential that would lead to the perception of pain.



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Physio Ex 9.0 Exercise 3 Review Sheet Neurophysiology of Nerve Impulses
Feb 16, 2012

Thank you so much. I have answered all of the questions except for this question which I still can't figure out.

Activity 1: The Resting Membrane Potential
3. Explain why a change in extracellular Na+ did not alter the membrane potential in the resting neuron.



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Reply# 3
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Physio Ex 9.0 Exercise 3 Review Sheet Neurophysiology of Nerve Impulses
Feb 16, 2012

3. Explain why a change in extracellular Na+ did not alter the membrane potential in the resting neuron.

There are less .



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gato guevara
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Physio Ex 9.0 Exercise 3 Review Sheet Neurophysiology of Nerve Impulses
Apr 1, 2012

What does lidocaine do to volttage gated Na+ channels?



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Physio Ex 9.0 Exercise 3 Review Sheet Neurophysiology of Nerve Impulses
Apr 12, 2012

Activity 2
1. K+ channels are possibly present. Because they are passive BUT selective. The K+ ions will readily travel back and forth down their concentration gradient.
2. States there is a slight difference in charge along the cell, "brief localized changes in membrane potential".
3. The pacinian corpuscle is very susceptible to pressure. more pressure = greater change
4. Chemicals (smell) will have the largest effect.
5. It is unlikely that neither the pacinian corpuscle or free nerve ending would be affected by isoamyl acetate because they didn't have any change from chemicals(smell).



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Physio Ex 9.0 Exercise 3 Review Sheet Neurophysiology of Nerve Impulses
Apr 12, 2012

Activity 3
1. The voltage at which the all or non response takes place, at around -50mv, the threshold is reached and causes an action potential.
2. Depolarization, causes the action potential because it increases the potential towards 0. (positive direction)
3. There was no change in the action potential validating the all or none response, there should NEVER be a change in action potential.
4. Unless threshold potential is reached, nothing will happen.
5. The axon hillock



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Physio Ex 9.0 Exercise 3 Review Sheet Neurophysiology of Nerve Impulses
Apr 12, 2012

Activity 4
1. TTX irreversibly blocks voltage gated sodium channels.
2. Lidocaine unlike ttx, IS reversible; however, it does still close the channel.
3. No, because of the sum of them. Some axons would remain unchanged, possibly making the response greater than zero.
4. Fewer action potentials because of irreversibility ( blockage of the voltage gated channels)
5. Because it blocks membrane potential, but can be reversed.



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