26-5-2021 PhysioEx Exercise 3 Activity 1
PhysioEx Lab Report
Exercise 3: Neurophysiology of Nerve Impulses
Activity 1: The Resting Membrane Potential
Name:
Date:
Session ID:
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.
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?
https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex3/act1/ 1/7
, 26-5-2021 PhysioEx Exercise 3 Activity 1
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
Low Na+ Axon, intracellular -72
https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex3/act1/ 2/7
PhysioEx Lab Report
Exercise 3: Neurophysiology of Nerve Impulses
Activity 1: The Resting Membrane Potential
Name:
Date:
Session ID:
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.
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?
https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex3/act1/ 1/7
, 26-5-2021 PhysioEx Exercise 3 Activity 1
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
Low Na+ Axon, intracellular -72
https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex3/act1/ 2/7
