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Physio Ex 9.0 Exercise 3
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bionicman
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EXERCISE 3:  Neurophysiology of Nerve Impulses
ACTIVITY 1:  The Resting Membrane Potential   Answers
1.   The nervous system contains two general types of cells: neuroglia cells and     c. neurons
2.   The resting membrane potential of the neuron in this lab under the control conditions was _______ mV.   -70mV
3.   True or False:  For most neurons, the concentration of  Na+ and K+ ions inside and outside the cell are the primary factors that determine the resting membrane potential.      true
4.   Explain why increasing the extracellular K+ causes the membrane potential to change to a less negative value.
   Potassium ions diffuse out across the membrane, leaving behind a net negative charge.
5.   Discuss the relative permeability of the membrane to Na+ and to K+ in a resting neuron.   Membrane permeability to sodium is low because there are only a few sodium leakage channels. Sodium ions slowly diffuse inward, down their concentration gradient. If left unchecked, such inward leakage of sodium would destroy the resting membrane potential. The small inward leak of sodium and outward leak of potassium are offset by the sodium potassium pumps.
6.   Discuss how a change in Na+ or K+ conductance would affect the resting membrane potential.   The change in conductance of NA+ or K+ would affect the resting membrane potential because the resting membrane potential is a potential difference between eh inside of the cell and the outside of the cell across the membrane. It depends on the resting permeability of the membrane to ions and on the intracellular and extracellular concentrations of those ions to which the membrane is permeable.
ACTIVITY 2:  Receptor Potential
7.   The “receiving end” of a sensory neuron is called the sensory receptor.  It has proteins that can generate a signal called the _________ potential when the sensory neuron is stimulated.   receptor
8.   Which of the following is not a sensory modality?
a.   taste
b.   smell                  
c.   touch
d.   height   d. height
9.   The maximum amplitude of response of the Pacinian corpuscle to pressure in this simulation was ____ mV.   40mV
10.    Sensory neurons have a resting membrane 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?   Potassium leak channels
11.    What is meant by the term graded potential?    Graded potential are incoming signals which are short-lived, localized changes in membrane potential that can be either depolarizations or hyperpolarizations.
12.   Identify which of the stimulus modalities induced the largest amplitude receptor potential in the Pacinian corpuscle.    Pressure high, 40 mV
13.   Identify which of the stimulus modalities induced the largest amplitude receptor potential in the olfactory receptors.   Chemical high, 25mV
14.   What type of sensory receptor would likely respond to a green light?   photoreceptors
ACTIVITY 3:  The Action Potential: Threshold
15.   In this lab simulation, what stimulus voltage first caused voltage to be seen at R1 and R2?     _______ mV   20mV
16.   True or False:  A neuron must be polarized to the threshold voltage before an action potential is generated.       False
17.   If the resting membrane potential of a neuron is -70mV and the threshold voltage of that neuron is -50 mV, then the neuron must be depolarized by a minimum of ______ mV before an action potential is generated.
   c. 20mV
18.   Define the term threshold as it applies to an action potential.   Threshold is the minimal stimulus needed to generate an action potential.
19.   What change in membrane potential (depolarization or hyperpolarization) triggers an action potential?   I think that depolarization triggers an action potential.
20.   How did the action potential at R1 (or at R2) change as you increased the stimulus voltage above the threshold voltage?     It did not change, as the stimulus voltage was increased the peak at R1 and R2 stayed at 100.
21.   An action potential is an “all-or-nothing” event.  What does this mean?   The “all-or-nothing” event means that it happens completely or it doesn’t happen at all.
ACTIVITY 4:  The Action Potential: Importance of Voltage-Gated Na+ Channels
22.   According to your lab manual, “voltage-gated” channels open when the cell membrane of the neuron ___________.   depolarizes
23.   When Na+ ions flow through open channels into the neuron, then the membrane potential becomes
a.   more negative
b.   less negative
c.   closer to, at, or above the threshold voltage
d.   both b. and c.    d. both b and c
24.   True or False:  When a voltage-gated Na+ channel is closed, then the Na+ ions actually flow in the opposite direction than if the channel is open.   false
25.   What does TTX do to voltage-gated Na+ channels?   TTX irreversibly blocks voltage-gated sodium channels
26.   What does lidocaine do to voltage-gated Na+ channels?  How does its effect differ from the effect of TTX?   Lidocaine binds to voltage-gated sodium channels, and prevents the flow of sodium ions, whereas, TTX irreversibly blocks voltage-gated sodium channels. This is why lidocaine is used in dental procedures and not TTX.
27.   Why are fewer action potentials recorded at R2 when TTX is applied between R1 and R2?     TTX blocks the propagation of the action potential from R1 and R2.
28.   Why are fewer action potentials recorded at R2 when lidocaine is applied between R1 and R2?   Lidocaine blocked the propagation of the action potential from R1 and R2.
29.   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?   The dentist should inject the lidocaine into the particular nerves in the mouth depending where the pain is.
ACTIVITY 5:  The Action Potential: Measuring Absolute and Relative Refractory Periods
30.   According to your lab manual, voltage-gated Na+ channels inactivate (close) about _______ milliseconds after they open.   1-2 milliseconds
31.   During the absolute refractory period, a neuron would need to be depolarized by _____ mV before another action potential could be generated.
a.   50 mV
b.   75 mV   
c.   100 mV
d.   Another action potential cannot be generated   d. another action potential cannot be generated
32.   True or False:  In this lab simulation, when the interval between stimuli was 7.5 msec and the stimulus voltage was 60 mV, a second action potential was seen.   true
33.   Define the absolute refractory period.   The absolute refractory period is the interval at which the second action potential fails, the time after an action potential when the neuron can’t fire a second action potential, no matter how intense the stimulus.
34.   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 as the interval between the stimuli was decreased.
35.   Why is it harder to generate a second action potential during the relative refractory period?   It is harder to generate a second action potential during the relative refractory period because only partial repolarization has occurred and the stimulus has to be increased enough for it to happen. A second action potential can only occur after the axon has recovered from the absolute refractory period and the entire relative refractory period.
ACTIVITY 6:  The Action Potential:  Coding for Stimulus Intensity
36.   In the previous activities, you should have noticed that the amplitude (height) of the action potential
a.   is always the same.
b.   is an all-or-none event.   
c.   depends on the intensity of the stimulus.
d.   Both a. and b. are true.   d. both a and b are true
37.   True or False:  It is important for the body to be able to determine the intensity of a stimulus.    true
38.   In this lab simulation, when the stimulus voltage was 30 mV, the ISI was 62msec.  This codes for an action potential frequency of _______ Hz.   F= 1/62 Hz; f=1/62= 0.0161
39.   Why does the frequency of action potentials increase when the stimulus intensity increases?   The frequency increases because the longer stimuli allows for the axon of the neuron to generate additional action potentials as soon as they recover from the first, the length of the recovery period changes depending on the stimulus intensity.
40.   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 intensity is increased.
ACTIVITY 7:  The Action Potential: Conduction Velocity
41.   True or False:  All of the axons in the human body conduct the nerve impulse (action potential) at the same velocity.   false
42.   Which of these three axons was able to conduct the action potential the fastest?
a.   The A fiber
b.   The B fiber      
c.   The C fiber
d.   All velocities were the same   A. the A fiber
43.   In this simulation, the conduction velocity of the A fiber was ______ m/sec; the conduction velocity of the B fiber was ______ m/sec; the conduction velocity of the C fiber was ______ m/sec.   50, 10, 1
44.   What is the effect of axon diameter on the conduction velocity?   Increases in the axon diameter increase the conduction velocity.
45.   What is the effect of the amount of myelination on conduction velocity?   The amount of myelination on an axon affects the conduction velocity because the more myelination the better the conduction velocity.
46.   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 for each axon because of the amount of myelination on each axon.
ACTIVITY 8:  Chemical Synaptic Transmission and Neurotransmitter Release
47.   The synapse is the location where the axon of one neuron communicates with    d.  any or all of the above
48.   Neurotransmitter is released into the synaptic gap by a process called   c. exocytosis
49.   The name of the specific neurotransmitter released at a synapse between a motor neuron and a muscle cell is ____________.     acetylcholine
50.   When the stimulus intensity is increased, what changes: the number of synaptic vesicles released or the amount of neurotransmitter per vesicle?    number of synaptic vesicles
51.   What happened to the amount of neurotransmitter released when you switched from the control extracellular fluid to the extracellular fluid with no Ca2+?   When I switched from the control extracellular fluid to the extracellular fluid with no CA2+ no neurotransmitters were released
52.   What happened to the amount of neurotransmitter released when you switched from the extracellular fluid with no Ca2+ to the extracellular fluid with low Ca2+?   When the low Ca2+ ions were added a small amount of neurotransmitter was released.
ACTIVITY 9:  The Action Potential…Putting It All Together
53.   True or False:  The amplitude of the depolarization that can result at the postsynaptic receptor is always the same.   false
54.   In this simulation, when the sensory neuron membrane potential at the receptor was -40mV, the interneuron membrane potential at the “receiving end” was ______ mV.   -50 mV
55.   In this simulation, with a “strong stimulus”, _____ sensory neuron vesicles were released from the axon terminal.   a. many, many
56.   Describe what happened when you applied a very weak stimulus to the sensory receptor.   When a very weak stimulus was applied to the sensory receptor, a small depolarizing response occurred at R1, and no responses occurred at R2,R3, and R4.
57.   Describe what happened when you applied a moderate stimulus to the sensory receptor.   When a moderate stimulus was applied to the sensory receptor a larger depolarizing response occurred at R1, and an action potential was generated at R2 and R4
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.)   A graded receptor potential was created at R1 and R3, and an action potential was created at R2 and R4 when a moderate stimulus was applied.
59.   Describe what happened when you applied a strong stimulus to the sensory receptor.   When a strong stimulus was applied to the sensory receptor action potential were created at all four locations


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Reply# 1
Biggie
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Physio Ex 9.0 Exercise 3
May 2, 2012

Holy cow... Thank you so much... I appreciate it a lot.



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Physio Ex 9.0 Exercise 3
Sep 20, 2012

Holy cow... Thank you so much... I appreciate it a lot.
Your welcome, by chance have you taken biology scin 130?



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Physio Ex 9.0 Exercise 3
Sep 21, 2012

Awesome! I have most of the pre and post quizzes posted on here



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Physio Ex 9.0 Exercise 3
Sep 22, 2012

Awesome! I have most of the pre and post quizzes posted on here
I have been looking but i only see one with  questions



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Physio Ex 9.0 Exercise 3
Sep 22, 2012

Awesome! I have most of the pre and post quizzes posted on here
I have been looking but i only see one with  questions


Go to my profile and hit the search my topics.



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