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(Solved) LABORATORY REPORT Activity: Action Potentials Name: Thomas Budnik Instructor: Date:2017 Predictions 1. Exceeding threshold depolarization at the...


I originally put my answer as 1-2 msec the absolute refractory period is 1 msec or less relative is 3-4 msec I believe but some neurons can have up to 15 msec I am having trouble answering this as I do not know what they are looking for I believe they want 1 msec or less but I am not sure any help is appreciated.

LABORATORY REPORT
Activity: Action Potentials Name: Thomas Budnik Instructor:
Date: 04.15.2017 Predictions
1. Exceeding threshold depolarization at the trigger zone______the likelihood of generation of an action potential.
increases
2. Action potential amplitude
does not change with distance
3. Increasing frequency of stimulation to the trigger zone
increases number of action potentials Materials and Methods
Experiment 1: Effect of Stimulus Strength on Action Potential Generation
1. Dependent Variable
membrane potential
2. Independent Variable
stimulus strength (voltage)
3. Controlled Variables
frequency of stimulation, type of neuron Experiment 2: Effect of Frequency of Stimulation on Action Potential Generation
1. Dependent Variable
membrane potential
2. Independent Variable
frequency of stimulation
3. Controlled Variables
stimulus strength (voltage), type of neuron 4. Which part of the neuron was stimulated?
Neurons are stimulated at the dendrite.
5. Where was membrane potential measured?
At the axon and axon hillock.
6. What was used to measure membrane potential?
The patch clamp and voltage dependent fluorescent dye. Results
Table 3: Change in Membrane Potential From Axon Hillock to Axon
a. Values of maximal depolarization of membrane potential (mV) at different stimulation voltages, by location.
Location
Axon hillock 0 V (no stimulation )
-68.3 2V
-63.8 Laboratory Report/ Thomas Budnik/ Action Potentials/ / 04.15.2017/ Page [1] of [4] Stimulation Voltage
4V
-56.3 6V
30.3 8V
29.9 Location
Axon 2V
-72.4 Stimulation Voltage
4V
-64.3 6V
30.7 8V
-68.5 0 V (no stimulation )
NO 2V
NO Stimulation voltage
4V
NO 6V
Yes 8V
Yes 0.2 8.6 8 -0.4 98.4 0 V (no stimulation )
-68.5 b. Action Potential Generation.
Location
Action potential
generated?
Change in membrane
potential with distance Graph 1. Maximal depolarization of membrane potential at axon hillock and axon after different
stimulation voltages. Resting membrane potential = -70 mV.
1. What was the resting membrane potential (no stimulation) recorded in Table 3?
-68.3 at the axon hillock and -68.5 at the axon.
2. At which stimulation voltage(s) did you see decrimental conduction of graded potential from axon hillock to axon?
At 2V.
3. At what stimulus voltage(s) did an action potential occur?
At 6V.
4. What was the membrane potential at the axon hillock when the action potential was generated?
Was 30.3 at axon hillock. 5. For each of the stimulation voltages, indicate whether it was sub-threshold, threshold, or suprathreshold.
a) 2V
Sub-threshold.
b) 4V
Sub-threshold.
c) 6V
Threshold.
d) 8V
Suprathreshold. Table 4: Effect of Supra-Threshold Stimulation Frequency on Action Potential Generation.
Period between
stimulations (ms)
Number of Action
Potentials Produced 25 Hz
40 msec
5 Frequency of the Five Supra-Threshold Stimuli
50 Hz
100 Hz
200 Hz
20 msec
10 msec
5 msec
5 Laboratory Report/ Thomas Budnik/ Action Potentials/ / 04.15.2017/ Page [2] of [4] 3 1 400 Hz
2.5 msec
1 Refractory period
effect? 25 Hz
NO Frequency of the Five Supra-Threshold Stimuli
50 Hz
100 Hz
200 Hz
NO
Yes
Yes 400 Hz
Yes Graph 2. Number of action potentials generated at different times between stimulations. 6. State the amount of time between stimulations for each frequency of stimulation.
a) 25 Hz
40 msec.
b) 50 Hz
20 msec.
c) 100 Hz
10 msec.
d) 200 Hz
5 msec.
e) 400 Hz
2.5 msec. 7. For each frequency of stimulation, indicate whether the period between stimulation is longer or shorter than the length of an action
potential. Length of action potential in pyramidal neuron is about 15-20 milliseconds (msec).
a) 25 Hz
Longer.
b) 50 Hz
Same.
c) 100 Hz
Shorter.
d) 200 Hz
Shorter.
e) 400 Hz
Shorter. 8. Estimate the length of the refractory period for the pyramidal neuron.
The absolute refractory period is 1 msec. The relative refractory period is 3-4 msec. Discussion
Laboratory Report/ Thomas Budnik/ Action Potentials/ / 04.15.2017/ Page [3] of [4] 1. In Experiment 1, discuss why the amplitude of the action potential did not increase as stimulation voltage increased above
threshold.
Action potential and stimulation voltage are all or nothing. The amplitude of the action potential did not increase it stays the same. So the
amplitude remains constant in depolarization as the action potential moves down the length of an axon.
2. In Experiment 1, explain why the membrane potential between the axon hillock and axon either changed or did not change with
subthreshold stimulus. Differences of 1.0 mV or less are not significant.
The subthreshold stimulus did not change much at the axon hillock and axon membrane. The subthreshold stimulus did not result in the creation
of an axon action potential.
3. In Experiment 2, explain why the membrane potential between the axon hillock and axon either changed or did not change with
threshold stimulus. Differences of 1.0 mV or less are not significant.
The stimulus either reached threshold and caused Na+ to cross and generate an action potential or it didn't. The threshold stimulus results in an
action potential, but membrane potential remained the same between the axon hillock and the axon.
4. In Experiment 2, explain why the number of action potentials generated varied with increased stimulation frequency.
The frequency and intensity of a stimulus increases the action potential and increases firing of neurons until the threshold is met by the
refractory period. The refractory period inhibited more action potentials.
5. Restate your predictions that were correct and give the data from your experiment that supports them. Restate your predictions
that were not correct and correct them, giving the data from your experiment that supports the correction.
Exceeding threshold depolarization at the trigger zone increases action potential was correct, at 6 volts eough energy was created to creat an
action potential which foloowed through in 8 v. Action potential amplitude does not change with distance was correct was 68.3 at the hillock and
68.5 at the axon. Increasing frequency of stimulation to the trigger zone increases number of action potentials was correct and did increase # of
AP unless it fell on a refractory period. Application
1. ECF potassium levels affect resting membrane potential. Hyperkalemia (excessive levels of potassium in the blood) and
hypokalemia (abnormally low blood potassium levels) both affect the function of nerves and muscles.
a. Explain how hyperkalemia will initially affect the resting membrane potential and the generation of an action potential.
Hyperkalemia increases K in the cells creating a more positive charge, this causes the cells to become more excitable increasing action
potential.
b. Explain how hypokalemia will initially affect the resting membrane potential and the generation of an action potential.
Hypokalemia does the opposite it makes the cell more negative and decreases excitable which causes a decrease in the action potential. 2. Tetrodotoxin, a toxin found in puffer fish, acts by inhibiting voltage-gated sodium channels. Eating improperly prepared puffer fish
sushi can be fatal because of interference with action potential generation. Explain how tetrodotoxin interferes with action potential
generation.
Action potential relies on the movement of Na+. The toxin prevents the movement of sodium through the sodium channel. Without the
movement of Na+, the action potential can not be generated. Laboratory Report/ Thomas Budnik/ Action Potentials/ / 04.15.2017/ Page [4] of [4]

 


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