Virtual Neurons 2.0
Gabe Al-Ghalith
Janet M Dubinsky
7/31/12
• Everyone turn on your computers and get
web access via UMN guest.
• Hook up 1 computer at the table to your
table monitor. Turn both monitor and
computer on.
• Go to http://brainu.org/virtual-neuronssneak-peek
• Click “click here”
• Click start
• Check Show Graph & Action Potential
Meters.
• Click Continue
As an individual, work through 1-5, then as a group do 6: 5 min
1. What do you see?
2. What does it remind you of?
3. How does it make you feel?
4. What questions does it raise?
5. Speculate on what you think you should do next.
6. Plan a course of action as a group.
As a group, make the following circuits, 5 min.
1.
2.
3.
4.
5.
Make the muscle twitch using 2 neurons.
How fast is it twitching?
What are the ticks on the graph?
What are the lines on the graph?
Explain the relationships between the
firing rates of the different neurons and
the muscle twitching rate.
6. Write an equation for # of muscle
twitches, m, as a function of time, t.
How to manipulate pieces and buttons and read graph.
m = (t-2)/2 = t/2 - 1
m
t
Idea: Use PrintScreen to capture a circuit and paste it in a doc or ppt notebook.
Make these changes to your circuit, 5 min.
1. The Action Potential Threshold meters are
on the left panel.
2. Click on the threshold meter for your
motor neuron.
3. What happened to the muscle twitch rate?
4. If you click on the meter again, what do
you predict will happen to muscle
twitching?
5. What is meter #7 for?
6. What will happen if you click on the meter
for your sensory neuron? Try it.
How to change thresholds
As an individual or as a group, make the following circuits: 5 min
1. Make the muscle twitch using 3 neurons with all
threshold meters set to 2.
2. How fast is the muscle twitching now?
3. Why? How does this compare with your previous
2 neuron circuit?
4. What happens if you use interneuron 7 instead of
interneuron 3 or 4?
5. What happens when you change thresholds in this
circuit.
6. Make the muscle twitch using both interneurons 3
and 4.
7. Explain how this last circuit works using the
information from the graph.
Interneurons: Excitatory & Inhibitory
As an individual, make the following circuits 5 min
1. Start with 3 neuron circuit.
2. Click Settings; check Advanced Neuron
Shapes; click Continue
3. Click Change , Click the sensory neuron cell
body & choose 3rd shape from bottom.
4. Adjust positions & length of interneuron using
Change button, if necessary.
5. What’s muscle twitch rate now? How does this
compare to previous 2 circuits?
6. Describe the effect of the extra process. Use
data & observations to support your claims.
7. Why is this called Feed Forward?
Shape changes & Feed forward
As an individual, make the following circuits 5 min
1. Start with simple 3 neuron circuit
2. Change the shape of the motorneuron to
be branched.
3. Use the Add & Change buttons to build a
Feedback Loop onto the interneuron or
motorneuron dendrites.
4. What does this feedback do to the rate of
muscle firing? Why?
5. What happens when you play with
thresholds in this circuit?
Positive Feedback
What did I change in this circuit at 30 sec?
In pairs, use 1 computer to change the positive feedback circuit: 5’
1. Start with the same positive feedback circuit on
both computers.
2. On one computer, make the interneuron
feeding back onto the main circuit Neuron 7.
What do you predict will happen?
3. Use the graph to explain the differences in
firing rates between the two circuits.
4. Why is this called negative feedback?
5. What are some other instances in your life
when you’ve encountered + and – feedback?
6. Why do neuronal circuits need feedback?
Negative feedback & Homeostasis
At your table, make all of the following circuits. Save PrintScreen shots as proof you
made the circuits. First table to complete all circuits wins!
• Make the muscle twitch in a syncopated
rhythm!
• Make a circuit that begins with a
spontaneously firing interneuron.
• Make a circuit that uses 2 sensory
neurons to control the muscle firing.
• Use a spontaneously firing inhibitory
interneuron to control a circuit.
• Build a circuit that includes inhibiting the
spontaneously firing inhibitory interneuron.
Homeostasis
Input
Set Point
Comparator

Difference
Control
Center
Change
Signal
Output
Effector
Internal Measure of Output
Make a circuit of this Homeostatic System.
Internal Measure of Output
Output
Comparator
Σ
Difference
Effector
Control
Control
Center
Center
Set Point
Internal Measure of Output
Output
Σ
Difference
Effector
Set Points
Control
Center
How would you use this lesson in
your classroom?
This is alpha version. What should we
change in the beta version?