Physio Ex Exercise 3 Activity 4 PDF

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9/21/2020

PhysioEx Exercise 3 Activity 4

PhysioEx Lab Report Exercise 3: Neurophysiology of Nerve Impulses Activity 4: The Action Potential: Importance of Voltage-Gated Na + Channels Name: Kaelyn Wozniak Date: 21 September 2020 Session ID: session-9dcf0a9f-b6f6-6ac9-a0ee-43b66e8482ae

Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1 Voltage-gated Na + channels are membrane channels that open You correctly answered: when the membrane depolarizes. 2 When open, Na + channels allow You correctly answered: Na + ions to diffuse into the cell. 3 Which of the following is true of an action potential? You correctly answered: All of these answers are correct. 4 Which of the following can reduce the likelihood of an action potential? You correctly answered: All of these can reduce the likelihood of an action potential.

Experiment Results Predict Questions 1 Predict Question 1: If you apply TTX between recording electrodes R1 and R2, what effect will the TTX have on the action potentials at R1 and R2? Your answer: TTX will block the response at R2 but have no effect at R1. 2 Predict Question 2: If you apply lidocaine between recording electrodes R1 and R2, what effect will the lidocaine have on the action potentials at R1 and R2? Your answer: Lidocaine will block the response at R2 but have no effect at R1. Stop & Think Questions 1 Enter the peak value of the response at R1 and R2. You answered: 100 μV. i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex3/act4/

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PhysioEx Exercise 3 Activity 4

2 With a slower timescale, the appearance of the action potentials generated at R1 and R2 will appear to You correctly answered: be compressed in time but have the same peak value of response. 3 Why do you think TTX is not used during dental procedures? You correctly answered: TTX irreversibly blocks voltage-gated sodium channels in axonal membranes. Experiment Data Condition Stimulus Electrode Peak Peak Peak Peak Peak Voltage Value of Value of Value of Value of Value of (mV) Response Response Response Response Response (μV) 2 sec (μV) 4 sec (μV) 6 sec (μV) 8 sec (μV) 10 sec Control

30

R1

100

100

100

100

100

Control

30

R2

100

100

100

100

100

TTX

30

R1

100

100

100

100

100

TTX

30

R2

100

100

0

0

0

Lidocaine

30

R1

100

100

100

100

100

Lidocaine

30

R2

100

100

100

0

0

i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex3/act4/

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PhysioEx Exercise 3 Activity 4

Post-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1 In the control, the amplitudes of the action potentials at R1 and R2 are the same. Which of the following explains this? You correctly answered: All of these are reasonable explanations. 2 Blocking the voltage-gated Na + channels between R1 and R2 with TTX blocks You correctly answered: the propagation of the action potential from R1 to R2. 3 When voltage-gated Na + channels between R1 and R2 are blocked with TTX, an action potential is still recorded at R1 because You correctly answered: the voltage-gated Na + channels between the stimulus and R1 are unaffected by the TTX. https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex3/act4/

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PhysioEx Exercise 3 Activity 4

4 Puffer fish must be prepared carefully and properly before they can be eaten. Eating puffer fish can cause numbness of the lips, probably because You correctly answered: action potentials from sensory neurons in the lips are blocked.

Review Sheet Results 1 What does TTX do to voltage-gated Na + channels? Your answer: TTX blocks the diffusion of Na+ through the voltage-gated Na+ channels. 2 What does lidocaine do to voltage-gated Na + channels? How does the effect of lidocaine differ from the effect of TTX? Your answer: Lidocaine blocks the diffusion of Na+ through the voltage-gated Na+ channels. Its effect is different from TTX because it is usually used to block pain where as TTX is a poison. 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? Your answer: It would not be zero because the compound action potential does not ensure that all axons were affected. 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? Your answer: TTX blocked the sodium channels preventing the propagation of action potential from R1 to R2 therefore my prediction was correct. 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? Your answer: Lidocaine blocked the sodium channels preventing the action potential from propagating from R1 to R2. i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex3/act4/

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PhysioEx Exercise 3 Activity 4

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? Your answer: Lidocaine would be used to prevent the generation of action potential that would lead to the perception of pain.

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