Physio Ex Exercise 3 Activity 1 Lab11 PDF

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9/29/2020

PhysioEx Exercise 3 Activity 1

PhysioEx Lab Report Exercise 3: Neurophysiology of Nerve Impulses Activity 1: The Resting Membrane Potential Name: Kelly Date: 29 September 2020 Session ID: session-b0bbabbe-3018-b3dd-1691-3e196f2aad55

Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1 What is the approximate concentration of K + inside a typical cell (intracellular concentration)? You correctly answered: 150 mM. 2 What is the approximate concentration of K + outside a cell (extracellular concentration)? You correctly answered: 5 mM. 3 What is the approximate concentration of Na + inside a cell (intracellular concentration)? You correctly answered: 5 mM. 4 What is the approximate concentration of Na + outside a cell (extracellular concentration)? You correctly answered: 150 mM.

Experiment Results Predict Question 1 Predict Question: Predict what will happen to the resting membrane potential if the extracellular K+ concentration is increased. Your answer: The resting membrane potential will become less negative. Stop & Think Questions 1 What is the polarity of the resting membrane potential (voltage)? You correctly answered: negative. i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex3/act1/

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PhysioEx Exercise 3 Activity 1

2 What does it mean that the voltage just inside the membrane is negative? You correctly answered: There are more negative charges than positive charges just inside the membrane. 3 The membrane of most cells, including neurons, contains passive, open, K + leak channels. Given the normal K+ concentrations and the resultant concentration gradient, which direction would K+ be expected to move (diffuse) through these leak channels? You correctly answered: out of the cell . 4 What effect does increasing extracellular K + have on the net diffusion of K + out of the cell? You correctly answered: It decreases the net diffusion of K +. 5 Which way would Na+ move across the membrane if there were open Na + channels? You correctly answered: Na + would diffuse into the cell. 6 The membrane has open K+ channels, and changing extracellular K + concentration results in a change in membrane potential. Changing the extracellular Na + concentration does not significantly change the membrane potential. What do your results suggest about the number or state (open or closed) of Na + channels in the resting membrane of a neuron? You correctly answered: Na + channels are mostly closed. Experiment Data Extracellular Fluid (ECF)

Microelectrode Position

Voltage (mV)

Control

Cell body, extracellular

0

Control

Cell body, intracellular

-70

Control

Axon, extracellular

0

Control

Axon, intracellular

-70

High K+

Axon, intracellular

-40

High K+

Axon, extracellular

0

High K+

Cell body, extracellular

0

High K+

Cell body, intracellular

-40

Low Na+

Cell body, intracellular

-72

Low Na+

Cell body, extracellular

0

Low Na+

Axon, extracellular

0

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PhysioEx Exercise 3 Activity 1

Low Na+

Axon, intracellular

-72

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Post-lab Quiz Results You scored 100% by answering 3 out of 3 questions correctly. https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex3/act1/

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PhysioEx Exercise 3 Activity 1

1 A negative membrane potential was recorded when the tip of the microelectrode was You correctly answered: both inside the cell body and inside the axon. 2 Which of the following caused a change in membrane potential from -70 to -40 in the cell body? You correctly answered: an increase in extracellular K +. 3 Which of the following has the most negative voltage? You correctly answered: between the inside of the axon and the outside of the axon with control K+ ECF.

Review Sheet Results 1 Explain why increasing extracellular K + reduces the net diffusion of K + out of the neuron through the K + leak channels. Your answer: It changes the diffusion. 2 Explain why increasing extracellular K + causes the membrane potential to change to a less negative value. How well did the results compare with your prediction? Your answer: The results was accurate to my prediction. It causes it to change to a less negative value because it changes the diffusion. 3 Explain why a change in extracellular Na + did not significantly alter the membrane potential in the resting neuron? Your answer: Because the Na channels are mostly closed. 4 Discuss the relative permeability of the membrane to Na + and K + in a resting neuron. Your answer: K+ has leaky channels and Na+ channels are mostly closed. 5 Discuss how a change in Na+ or K + conductance would affect the resting membrane potential. i https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex3/act1/

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Your answer: high concentration of K+ out of the cell decreases the net diffusion of K+ and Na+ channels are mostly closed so it doesn't make a huge difference.

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