BIO 3303 Assignment #1: Neuron Model ( /5)
Due Sept. 27th
Neurophysiologists routinely use computer simulations to explore questions about neural
processing mechanisms. Neural models incorporate a number of physiological variables,
including Na + and K +concentrations and conductances, and stimulus parameters, including
stimulus voltage and frequency, to closely approximate natural responses.
In this assignment, you will be using a web-based neural simulation software* to explore neuron
function. The simulation file “neuron_model4.swf” initiates an experimental simulation that
models the response of a neuron to stimulus current pulses.
Complete the following steps and submit the answers to the questions (Q1-Q6) electronically
Part A- Neural simulation software
To run the experiment, click “Start Experiment”.
The initial parameters are set so that when the experiment is started, a standard action
potential occurs. The "Reset Values" button brings you back to these initial values. You can
change the values in the 2 upper left panels. The left panel sets the physiological variables of the
neuron and the right panel sets the variables of the applied stimulus. The results of the
experiment are displayed on graphs.
Question 1: What is the membrane potential change during the standard action potential
(difference from resting to maximum depolarization)? (0.5 mark)
The conductance is an index of membrane permeability. Change the maximum K conductance
value to 0 uA/mV/cm . Click “start experiment”. Observe what happens with to the membrane
potential after the stimulus (current) is applied.
Click on “reset values”. Change the [K+] outvalue to 108 mM. Click “start experiment”. Observe
what happens to the membrane potential after the stimulus is applied.
Question 2: Explain what happens to the K+ ions movement from inside to outside of the cells
in the two situations described above. Explain your reasoning for each situation. (1 mark)
Reset values. Change pulse type to: “repeated”. Set time between pulses to 10 ms. Start
Question 3a: Why are there only 2 action potentials when 3 separate stimuli were applied? In
other words, why the 2 pulse did not produce an action potential? (0.5 mark)
DO NOT reset values. Double the pulse ampli