Physio Ex Exercise 3 Activity 3 PDF

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9/21/2020

PhysioEx Exercise 3 Activity 3

PhysioEx Lab Report Exercise 3: Neurophysiology of Nerve Impulses Activity 3: The Action Potential: Threshold Name: Kaelyn Wozniak Date: 21 September 2020 Session ID: session-a708e637-6abd-6b6f-2d36-7be177a630ee

Pre-lab Quiz Results You scored 75% by answering 3 out of 4 questions correctly. 1 Axons are You correctly answered: long, thin structures that extend from a neuronal cell body. 2 Which of the following is easier? Your answer: Intracellular and extracellular recordings of the action potential are equally difficult. Correct answer: Extracellular recordings of the action potential. 3 An action potential is usually initiated in an axon at or near You correctly answered: all of the above. 4 The initiation of an action potential in a sensory neuron in the body normally You correctly answered: follows a sufficiently large depolarizing receptor potential.

Experiment Results Predict Question 1 Predict Question: How will the action potential at R1 (or R2) change as you continue to increase the stimulus voltage? Your answer: The peak value of the action potential will increase. Stop & Think Questions 1 Why is the action potential recorded by the second recording electrode (R2) delayed relative to the action potential recorded by the first recording electrode (R1)? You correctly answered: The action potential had to propagate from R1 to R2. i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex3/act3/

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PhysioEx Exercise 3 Activity 3

2 An increase in extracellular K + would depolarize a neuron. This depolarization would occur if neurons were damaged. From what you have just learned about generating an action potential, what effect would this have on nearby axons? The nearby axonal membranes will _______. You correctly answered: be depolarized to values near or above threshold voltages. Experiment Data Stimulus Voltage (mv)

Peak Value at R1 (μV) Peak Value at R2 (μV)

Action Potential

10

0

0

No

20

100

100

Yes

30

100

100

Yes

40

100

100

Yes

50

100

100

Yes

i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex3/act3/

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9/21/2020

PhysioEx Exercise 3 Activity 3

Post-lab Quiz Results i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex3/act3/

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9/21/2020

PhysioEx Exercise 3 Activity 3

You scored 33% by answering 1 out of 3 questions correctly. 1 The threshold voltage in an axon is usually Your answer: the same value as the resting membrane potential. Correct answer: less negative than the resting membrane potential. 2 If a graded receptor potential made the resting membrane potential of the axon more negative (for example, -70 mV changes to -75 mV), you would expect You correctly answered: it to be more difficult for this axon to reach the threshold voltage. 3 Failure to reach the threshold voltage in the axon of a sensory neuron could be caused by Your answer: generation of a receptor potential that makes the axonal resting membrane potential more negative. Correct answer: all of the above.

Review Sheet Results 1 Define the term threshold as it applies to an action potential. Your answer: Threshold is the voltage that must be reached in order to generate an action potential. Its the level of stimulation needed to trigger a neural impulse. 2 What change in membrane potential (depolarization or hyperpolarization) triggers an action potential? Your answer: Depolarization causes changes in the membrane potential by sodium rushing in the interior of the cell. 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: The action potential did not change this is because threshold is met. Therefore my prediction was wrong. 4 An action potential is an "all-or-nothing" event. Explain what is meant by this phrase Your answer: i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex3/act3/

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PhysioEx Exercise 3 Activity 3

This means once the threshold is met the action potential occurs if the stimulus is to small nothing happens. 5 What part of a neuron was investigated in this activity? Your answer: The trigger zone was investigated this is where the axon hillock and initial segment meet.

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