PhysioEx Lab Report
Exercise 3: Neurophysiology of Nerve Impulses Activity 1: The Resting Membrane Potential Name: ACH RIFANDI
Date: 5 February 2025
Session ID: session-7b5985ba-dc8b-db89-404e-73e4e5c1c3d3
Pre-lab Quiz Results
You scored 100% by answering 4 out of 4 questions correctly.
Experiment Results
Predict Question
Stop & Think Questions
What is the approximate concentration of K inside a typical cell (intracellular concentration)?
You correctly answered: 150 mM.
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What is the approximate concentration of K outside a cell (extracellular concentration)?
You correctly answered: 5 mM.
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What is the approximate concentration of Na inside a cell (intracellular concentration)?
You correctly answered: 5 mM.
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What is the approximate concentration of Na outside a cell (extracellular concentration)?
You correctly answered: 150 mM.
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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 more negative.
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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
Low Na+ Axon, intracellular -72
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 .
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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 .
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Which way would Na move across the membrane if there were open Na channels?
You correctly answered: Na would diffuse into the cell.
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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.
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2/5/25, 10:02 AM PhysioEx Exercise 3 Activity 1
https://media.pearsoncmg.com/bc/bc_0media_ap/physioex//10/ex3/act1/ 2/7
2/5/25, 10:02 AM PhysioEx Exercise 3 Activity 1
https://media.pearsoncmg.com/bc/bc_0media_ap/physioex//10/ex3/act1/ 4/7
Post-lab Quiz Results
You scored 100% by answering 3 out of 3 questions correctly.
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.
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2/5/25, 10:02 AM PhysioEx Exercise 3 Activity 1
https://media.pearsoncmg.com/bc/bc_0media_ap/physioex//10/ex3/act1/ 6/7
Review Sheet Results
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 . 2
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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.
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Explain why increasing extracellular K reduces the net diffusion of K out of the neuron through the K leak channels.
Your answer:
It is due to maintain an ion balance between the extraceluller and the extraceluller.
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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:
This is because k is the positive ion that caused the intracellular to lose the ion The positive was high, so the potential membranes became even more negative.
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Explain why a change in extracellular Na did not significantly alter the membrane potential in the resting neuron?
Your answer:
This is because the proteins in the cells are negative ions and are many in number, so these are less affected and are less permeable to eat so few are able to get into the cells.
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Discuss the relative permeability of the membrane to Na and K in a resting neuron.
Your answer:
Ion is so games that it easily gets out of cells and We'll be out of cell. However, ions are less permeable to bear it There's only a handful of them to get into a cell.
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