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Physioex 9.0 ex 3
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mercym35
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OMG, somebody help!!

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Reply# 1
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3 years ago

I got a 93 but I changed the answers that my teacher corrected so you should get a 100!!


1.   c
2.   -70
3.   True
4.   Potassium ions is the highest inside the cell. If they diffuse out across the membrane this would leave the RMP less negative.
5.   Membrane permeability to sodium is very low because there are only a few sodium leakage channels. Sodium ions do slowly diffuse inward, down their concentration gradient. Left unchecked, such inward leakage of sodium would eventually destroy the resting membrane potential.
The small inward sodium leak and outward leak of potassium leak are offset by the sodium potassium pumps.
6.   The resting period potential is a potential difference between the 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.   action
8.   D
9.   40
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.   with an appropriate stimulus of a sensory receptor, the amplitude of the receptor potential increases with the intensity of the stimulus.  A potential change such as this, which depends on the intensity of the stimulus, is called a graded potential.
12.   High pressure produced the largest amplitude receptor potential in the Pacinian corpuscle.
13.   High chemical produced the largest amplitude potential in the olfactory receptors.
14.   Photoreceptors
ACTIVITY 3:  The Action Potential: Threshold
15.   20
16.   true
17.   C
18.   Threshold applied to an action potential is the membrane voltage that must be reached to trigger an action potential.
19.   Action potentials are triggered when enough depolarization accumulates to bring the membrane potential up to threshold.
20.   It did not change, as the stimulus voltage was increased the peak value at R1 and R2 stayed at 100.
21.   This means that there is either going to be enough stimulation to cause an action potential or there is not going to be enough stimulation, there is no in between. It is either going to happen or it is not.
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
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?   age-gated sodium ions, and prevents the flow of sodium ions. TTX irreversibly blocks voltage-gated sodium channels, which is why it is not used during dental procedures.
27.   Why are fewer action potentials recorded at R2 when TTX is applied between R1 and R2?     TTX blocks the propagations of the action potential from R1 to 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 to 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?   A dentist would inject lidocaine into certain nerves of the mouth depending on 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
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
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.   It is the period immediately following the firing of a nerve fiber when it cannot be stimulated no matter how great a stimulus is applied.
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 when I decreased the interval.
35.   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:  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
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.   1/62 or .0161 Hz
39.   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.
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 stimulus 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
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 axon diameter increase conduction velocity.
45.   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.
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 because of the amount of myelination.
ACTIVITY 8:  Chemical Synaptic Transmission and Neurotransmitter Release
47.   The synapse is the location where the axon of one neuron communicates with
a.   another neuron.
b.   a muscle fiber.   
c.   a sensory receptor.
d.   any or all of the above.   D
48.   Neurotransmitter is released into the synaptic gap by a process called
a.   secretion.
b.   excretion.   
c.   exocytosis.
d.   diffusion.   C
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?   More synaptic vesicles went underwent exocytosis and were released.
51.   What happened to the amount of neurotransmitter released when you switched from the control extracellular fluid to the extracellular fluid with no Ca2+?   Because the exocytosis of the synaptic vesicles is Ca2+- dependent, when the extracellular fluid contained no Ca2+, no neurotransmitter was 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 Ca2+ ions were added to the extracellular fluid, 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
55.   A
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?   There was no response at R3 because the very weak stimulus does not depolarize the axon of the sensory neuron threshold. No neurotransmitters 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?   With a moderate stiumulus a action potential did result and 4 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.)   The type of membrane potential that occurred with R1 and R3 was a graded stimulus. Then for R2 and R4 there was action potential.
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?   With a strong stimulus a graded stimulus occurred at R1 and R3 and an action potential occurred at R2 and R4. 6 vesicles were released. No the responses were not the same at R1 through R4.



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Reply# 2
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3 years ago

^ Awesome post... +1



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