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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
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Foriiiiz
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Seeking a more comfortable homework help environment? Homework Clinic
I need the answers to PhysioEx 9.0 Ex 3 Pre-Lab AND Activities only Portion. Thanks!

Last Edit: Jul 4, 2012 by Foriiiiz LoggedReport this PostReport Abuse

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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
Jul 4, 2012

Did you do a search for this? There are several posters who've quite generously answered your question already. Smile



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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
Jul 4, 2012

I have searched high and low and the only thing i've found is; for the REVIEW SHEET portion of this task. nothing on the Pre-Lab AND the Activities. HELP!!!!!



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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
Jul 4, 2012

Post the questions, I'll try to answer them.



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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
Jul 9, 2012

Try this thread: http://biology-forums.com/index.php?topic=8529.0

It's long, but several answer sheets were posted on various pages. I looked at quite a few of them, and I feel like one had did have the pre-lab quiz answers. I don't have the time to go through the documents right now though. Currently studying for 2 midterms myself :-/ Sorry.



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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
Sep 10, 2012

Sorry, all I have been able to find are the activities and reviews... it seems like most schools dont require the pre lab section, and thus no answers. Sorry.



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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
Sep 30, 2012

Thank you very much!



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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
Oct 3, 2012

Activity 1

1. Explain why increasing extracellular K+ reduces the net diffusion of K+ out of the neuron through the K+ leak
channels.
Your answer:
When extracellular K+ increases, less of it (K+) goes into the cell. Therefore, the cell depolarizes.
2. Explain why increasing extracellular K+ causes the membrane potential to change to a less negative value. How well
did the results compare with your prediction?
Your answer:
When K+ ions diffuse out of the membrane, it leaves behind a net negative charge, reulting in large anions that cannot cross
the membrane. The results appeared to support the prediction.
3. Explain why a change in extracellular Na+ did not significantly alter the membrane potential in the resting neuron?
Your answer:
There weren't as many Na+ leakage channels as there were K+ leakage channels. There also appeared to be more K+
channels open.
4. Discuss the relative permeability of the membrane to Na+ and K+ in a resting neuron.
Your answer:
The permeability of a membrane to Na+ is low. There are only a few Na+ leakage channels and usually diffuse inward due
to the concentration gradient. The permeability of a membrane to K+ is much higher, in which K+ ions diffuse out across the
membrane because there is a greater amount within the cell.
5. Discuss how a change in Na+ or K+ conductance would affect the resting membrane potential.
Your answer:
The resting membrane potential is really a potential difference between the inside of a cell and the outside of the cell across
the membrane. It is dependent on the resting permeability of a membrane to the ions













Activity2
Review Sheet Results
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?
Your answer:
Olfactory Receptor: Na+ ion channels
Pacinian Corpuscle: K+ leakage channels
Free Nerve Ending: Na+ ion channel
2. What is meant by the term graded potential?
Your answer:
A graded potential is a potential that is graded with stimulus intensity.With an appropriate stimulus, the amplitude of the
receptor potential increases with stimulus intensity. A graded potential is also referred to as a local potential.
3. Identify which of the stimulus modalities induced the largest amplitude receptor potential in the Pacinian corpuscle. How
well did the results compare with your prediction?
Your answer:
The high pressure modality induced the largest amplitude receptor potential in the Pacinian corpuscle. It had a peak value of
-30mv and an amplitude response of 40mv. The results appeared to support the 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?
Your answer:
The high chemical modality induced the largest amplitude receptor potential in the olfactory receptors. It had a peak value
response of -45 mv and an amplitude response of 25 mv. The results appeared to support the prediction.
5. The olfactory receptor also contains a membrane protein that recognizes isoamylacetate and, via several other
molecules, transduces the odor stimulus into a receptor potential. Does the Pacinian corpuscle likely have this
isoamylacetate receptor protein? Does the free nerve ending likely have this isoamylacetate receptor protein?
Your answer:
Neither the Pacinian corpuscle or the free nerving have an isaomylacetate receptor protein. This protein only responds to
chemical stimuli, in which the Pacinian corpuscle free nerven endings don't respond to.
6. What type of sensory neuron would likely respond to the green light?
Your answer:
The free nerve ending would likely respond to green lights. It was able to respond to different modalities because it is not as
specialized. It responded the most to a high heat stimulus at 50mv.















Activity 3
1. Define the term threshold as it applies to an action potential.
Your answer:
A threshold is a transmembrane potential at which an action potential begins.
2. What change in membrane potential (depolarization or hyperpolarization) triggers an action potential?
Your answer:
Depolarization 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?
Your answer:
Thea action potential at R1/R2 did not change as the stimulus voltage was increased. The results refuted the prediction.
4. An action potential is an "all-or-nothing" event. Explain what is meant by this phrase
Your answer:
Stimuli that bring the membrane to a threshold generate identical action potentials. Properties of the action potential do not
depend on the relative strength of depolarizing stimuli.
5. What part of a neuron was investigated in this activity?
Your answer:
The axon was investigated in this activity.







Exercise 4
1. What does TTX do to voltage-gated Na+ channels?Because the TTX irreversibly blocks the voltage-gated sodium channels.
2. What does lidocaine do to voltage-gated Na+ channels? How does the effect of lidocaine differ from the effect of TTX?
through the gated sodium ions which prevent the flow of sodium ions. TTX also irreversibly blocks voltage-gated sodium channels and that is the reason why it is not used during dental procedures.
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 be zero? Why or why not?
No the R2 would not be zero because although after 8 and 10 seconds zero was recorded it is the sum of the action potential that is being recorded and there is still a value at the 2, 4 and 6 second recordings.
4. Why are fewer action potentials recorded at recording electrodes R2 when TTX is applied between R1 and R2? How well did the results compare with your prediction?
TTX blocks the propagations of the action potential from R1 to R2 just as i predicted in my prelab quiz.
5. Why are fewer action potentials recorded at recording electrodes R2 when lidocaine is applied between R1 and R2? How well did the results compare with your prediction?
Lidocaine blocked the propagation of the action potential from R1 to R2.
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?
A dentist would inject lidocaine into certain nerves of the mouth depending on where the pain is.









Activity 5

1. Define inactivation as it applies to a voltage-gated sodium channel.
It is a gate blocks the inside of the channel shortly after it has been activated. Voltage-gated sodium channels are inactivated when the depolarized membrane potential is repolarizing and the K+ channels are open during this phase.
2. Define the absolute refractory period.
It is the period immediately following the firing of a nerve fiber when it cannot be stimulated regardless of how great a stimulus is applied.
3. How did the threshold for the second action potential change as you further decreased the interval between the stimuli?
The threshold for the second action potential increased when the interval was decreased.
4. Why is it harder to generate a second action potential during the relative refractory period?
This is because only partial repolarization has occurred, and only a greater than normal stimulus can cause an action potential to occur.















Activity 6

1. Why are multiple action potentials generated in response to a long stimulus that is above threshold?
The longer stimuli allow time for recovery and the above threshold allows the action potential to occur after the relative refractory period.
2. Why does the frequency of action potentials increase when the stimulus intensity increases?
When the intensity of the stimulus is increased, the size of the action potential does not become larger. Rather, the frequency or the number of action potentials increases.
3.How does the threshold voltage change during the relative refractory period? The threshold voltage changes by increasing in the relative refractory period, during this time a second action potential can be produced if the stimulus intensity is increased.
4. What is the relationship between interspike interval and the frequency of action potential?
The frequency of the action potentials is the reciprocal of the interspike interval with a conversion from milliseconds to seconds.


















Activity 7

1. How did the conduction velocity in the B fiber compare with that in A fiber? How well did the results compare with your prediction?
I believed that because the B fiber had a smaller diameter it would be slower which was accurate to the results.
2. How did the conduction velocity in the C fiber compare with that in fiber B? How well did the results compare with your prediction?
My prediction was accurate to the otcome in that The velocity of the B fiber was slower because it had a smaller diameter and less myelinated.
3. What is the effect of axon diameter on the conduction velocity? Increases in axon diameter increase conduction velocity.
4. What is the effect of the amount of myelination on conduction velocity? The amount of myelination affects the conduction velocity by more myelination the better the conduction velocity.
5. Why did the time between stimulation and the action potential at R1 differ for each axon? The time between stimulation and the action potential differed because of the amount of myelination.
6. why did you need to change the timescale on the oscilloscope for each axon?
This is necessary in order to see the action potentials. The velocity changes so when it get very slow you need a longer time scale.










Activity 8
Review Sheet Results
1. When the stimulus intensity is increased, what changes: the number of synaptic vesicles released or the amount of
neurotransmitter per vesicle?
Your answer:
When the stimulus intensity increased, the number of synaptic vesicles increased with the intensity.
2. What happened to the amount of neurotransmitter release when you switched from the control extracellular fluid to the
extracellular fluid with no Ca2+ ? How well did the results compare with your prediction?
Your answer:
When switching from the control extracellular fluid to the extracellular fluid with no Ca2+, no transmitters were released. The
results did not support the prediction.
3. What happened to the amount of neurotransmitter release when you switched from the extracellular fluid with no Ca2+
to the extracellular fluid with low Ca2+ ? How well did the results compare with your prediction?
Your answer:
When switching from the extracellular fluid with no Ca2+ to the extracellular fluid with low Ca2+, onlow a few
neurotransmitters were released with low Ca2+. The results did not support the prediction.
4. How did neurotransmitter release in the Mg2+ extracellular fluid compare to that in the control extracellular fluid? How
well did the result compare with your prediction?
Your answer:
Compared to the conotrol extracellular fluid, the neurotransmitter Mg2+ was released in a very small amount. The results did
not support the prediction.
5. How does Mg2+ block the effect of extracellular calcium on neurotransmitter release?
Your answer:
When Mg is added to the extracellular fluid, it will be oxidized to Mg2+. Mg will take the place of Ca as the reducing agent.



























Activity 9
1. Why is the resting membrane potential the same value in both the sensory neuron and the interneuron?
Your answer:
The resting membrane potential is the same value in both the sensory neuron and the interneuron because both the
sensory neurons and interneurons are already at resting potential, so there is nothing to stimulate it.
2. Describe what happened when you applied a very weak stimulus to the sensory receptor. How well did the results
compare with your prediction?
Your answer:
When a weak stimulus was applied to the sensory receptor, there was a very small response in the R1 receptor, but none at
R2, R3, and R4. The results supported the prediction.
3. Describe what happened when you applied a moderate stimulus was to the sensory receptor. How well did the results
compare with your prediction?
Your answer:
When a moderate stimulus was applied to the sensory receptor, all 4 had a response, but R1 and R3 had the greatest
graded potential. The results supported the prediction.
4. 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 (view Experiment Results to view the response to this stimulus).
Your answer:
A graded receptor potential was the type of membrane potential that occured at R1-R4 when a moderate stimulus was
applied.
5. Describe what happened when you applied a strong stimulus to the sensory receptor. How well did the results compare
with your prediction?
Your answer:
When a strong stimulus was applied to the sensory receptor, action potentials were generated at R1, R2, R3, and R4. The
results only supported part of the prediction.



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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
Oct 9, 2012

These are all great for the Review sheets!  BUT does anyone have the Activity questions/answers that are within the lab itself, NOT on the Review sheet.

For example, the first question in Exercise 3, Activity 1  is "Explain why the resting membrane potential had the same value in the cell body and in the axon."
Post Merge: Oct  9, 2012

I figured it out...most everyone is posting the Review Sheets.  I need help within the lab itself and the Activities.  Does that make sense?



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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
Dec 26, 2012

thanks for the help



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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
May 15, 2013

Hello dear folks im very interested in this website for getting quick answer for those question which people get difficulty.So i am also looking answer for Physio Ex 9 Exercise 11 Activity 1 and 4 .Thank you .



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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
Jul 6, 2013

were you able to open the attachment? because i cant



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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
Jul 10, 2013

I have some activity in pdf file that might be what you looking for.



Attached file(s)* PEX-03-03.pdf (122.15 KB - downloaded 89 times.)
* PEX-03-04.pdf (85.94 KB - downloaded 56 times.)
* PEX-03-07.pdf (75.76 KB - downloaded 61 times.)
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Need Answers to PhysioEx 9.0 exercise 3 pre-lab AND Activity portions only
Jul 10, 2013

i have the same questions but i guess i have to look around.



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