Crescent Loom

~ Exploration Guidebook ~

1. Introduction

This is your creature in the Action Potential Explorer.

Its neurons have been disabled so it’ll sit still while we poke at it. Click the blue hexagon to open up its brain.

This is your creature’s brain. The red and green shapes represent the cell body (soma) of each neuron. The black line is the axon of the green pacemaker neuron, and the black triangles are the locations where it synapses onto the two red motor neurons.

You have two tools on the right: a selecting needle and a stimulator.

Clicking a cell with the selecting needle will pop up a window with its name, a graph of the current membrane potential, and its ion channels.

But don’t worry about that for now. Try using the stimulator to zap everything and see what happens!

What happens when you stimulate parts of the brain?

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2. Membrane Voltage

Let’s take a closer look at the neurons to see what’s going on.

Use the selecting needle to open up the details of the axon.

The orange line is a graph of the membrane voltage (Vm), which represents how “excited” the neuron is.

Zap the part of the axon that you have selected to see what an excited Vm looks like.

The blue lines on the voltage graph represent how strongly Vm is being pulled towards the reversal potential for sodium (Na, top) and potassium (K, bottom). They’re relative to each other; the more Na channels that are open, the stronger its line gets and the weaker K’s influence becomes.

The dots & labels are the ion channels for the axon. Only the sodium and potassium leak channels are currently enabled. Leak channels are small (hence their tiny dots) but since K is slightly larger, the resting Vm is closer to K’s reversal potential.

What happens to Vm when you disable the leak channels?

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(Confusingly, the units for membrane voltage are in millivolts, or mV, so it’s possible to talk about the mV of the Vm)

3. Passive Conductance

The activity of one part of a neuron can affect those around it.

You can see multiple sections at once by holding shift while selecting bits of the cell.

What happens to nearby sections of axon when you zap their neighbor?

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Select a motor neuron & connecting axon. What happens to each when you zap the other?

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4. Active Conductance

The two other channels on the axon — the voltage-gated sodium channel (VGSC) and voltage-gated potassium channel (VGKC) — only do things when Vm hits a threshold.

Let’s explore what they do by turning them on one at a time.

Stimulate the axon while both are still off.

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Turn VGSC on and give the axon a short zap.

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Turn VGKC on and give the axon a longer zap.

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Turn both VGSC and VGKC on, then a short zap anywhere in the brain.

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At this point, we have a fully functional axon! Try poking around and stimulating different parts of the brain to see how the creature reacts.

5. How can I get it to move by itself?

Short answer: select the pacemaker soma ( ) and enable all of its channels.

Long answer: try to figure out how the pacemaker works by going through the process of turning on its channels one at a time, like you did with the axon!

Stimulate the pacemaker while both are still off.

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Turn Burst on and give the pacemaker a short zap.

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Turn Queer on and just watch.

Bonus: shift+click to inhibit instead of exciting the cell. How does it respond?

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Turn both Burst and Queer on! How do they work together?

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About

This simulation was created as part of Crescent Loom, an in-development game about weaving the bodies and brains of underwater creatures. It is independently designed and programmed by Olive Perry and was funded through Kickstarter.

If you have problems, questions, or requests, please let me know at ! This is still very much a work-in-progress, so feedback and suggestions are appreciated.

You can stay updated on development with my semi-monthly wickletter emails: