Probe and Identify Neurons
One the left is a view of the leech skin and ganglion preparation with the outside of the skin showing up. The small hole in the skin cut over the ganglion is visible in the center of the skin, lit from below with illumination. On the top right, a graph of Cell Potential in millivolts (mV) against time in seconds is shown. Y-axis spans from +40 to -120 mV from top to bottom, x-axis spans 1 second from left to right. On the bottom right, three tools are shown: A fine-bristled paintbrush, a dissecting probe with a blunt metal tip, and a dissecting forceps with fine tips. These will be later used to deliver mechanical stimuli to the leech’s skin.
Start the experiment.
One the left is a view of the leech skin and ganglion preparation with the outside of the skin showing up. The small hole in the skin cut over the ganglion is visible in the center of the skin, lit from below with illumination. On the top right, a graph of Cell Potential in millivolts (mV) against time in seconds is shown. Y-axis spans from +40 to -120 mV from top to bottom, x-axis spans 1 second from left to right. On the bottom right, three tools are shown: A fine-bristled paintbrush, a dissecting probe with a blunt metal tip, and a dissecting forceps with fine tips. These will be later used to deliver mechanical stimuli to the leech’s skin.
Resume to continue your progress from a previous session.
Start Over to clear your progress and begin.
Insert Electrode into a Single Neuron
The magnified view of the ganglion on the left shows black circles, indicating the locations of the cells you are exploring. Some are sensory cells, and others are not. It is up to you to find out how each cell responds to stimuli.
Click each neuron to insert an electrode, then observe the voltage display to the right. The display will change when the electrode penetrates the neuron. Electrical signals from the neuron are also fed into an audio amplifier, which produces an audio version of the signals displayed.
In the magnified view, the ganglion appears a pale-brown, diamond-shaped structure that contains many curly white lines that are the outlines of cell bodies of neurons. To the right of the screen is the display of voltage (y-axis) plotted against time (x-axis). At the moment, with the electrode outside the cells, there is a horizontal line corresponding to 0 volts on the y-axis.
You will explore five different neuron types. Click on one of the links below to insert an electrode into a neuron. The display area on the right will change when the electrode penetrates the neuron. Electrical signals from the neuron are also fed into an audio amplifier, which produces an audio version of the signals displayed.
Select a neuron:Review the neurons: Neuron 1Neuron T (Identified) Neuron 2Neuron X (Identified) Neuron 3Neuron N (Identified) Neuron 4Neuron R (Identified) Neuron 5Neuron P (Identified)
Insert Electrode into a Single Neuron
A colored circle with a letter indicates a neuron you have already identified. You can click on an identified neuron to review its information. When ready, click on a new neuron to insert the electrode into that neuron. If needed, review the full instructions here.
In the magnified view, the ganglion appears a pale-brown, diamond-shaped structure that contains many curly white lines that are the outlines of cell bodies of neurons. To the right of the screen is the display of voltage (y-axis) plotted against time (x-axis). At the moment, with the electrode outside the cells, there is a horizontal line corresponding to 0 volts on the y-axis.
You will explore five different neuron types. Click on one of the links below to insert an electrode into a neuron. The display area on the right will change when the electrode penetrates the neuron. Electrical signals from the neuron are also fed into an audio amplifier, which produces an audio version of the signals displayed.
You have identified one of each of the neuron types. Select a neuron below to review its information, or click 'Conclusion' to advance to the end.
Select a neuron:Review the neurons: Neuron 1Neuron T (Identified) Neuron 2Neuron X (Identified) Neuron 3Neuron N (Identified) Neuron 4Neuron R (Identified) Neuron 5Neuron P (Identified)
Test the Neuron's Response
Click the brush, probe, or forceps to stimulate the skin of the leech with that tool. Observe if the neuron responds to weak (brush), medium (probe), and strong (forceps) touch stimuli by generating action potentials, which will appear as spikes on the voltage display. Later, you will compare the responses you observe to published reference data. When you finish testing all the tools, press the "Continue" button.
Click the brush, probe, or forceps links below to stimulate the skin of the leech with that tool. Observe if the neuron responds to weak (brush), medium (probe), and strong (forceps) touch stimuli by generating action potentials, which will appear as spikes on the voltage display. Later, you will compare the responses you observe to published reference data. When you finish testing all the tools, click the "Continue" link.
Select: Brush Probe Forceps Continue or Probe a different neuron
Dye and View the Neuron
Push the "Dye Injection" button to inject a fluorescent dye from the tip of the electrode into the neuron's intracellular space. Push the "UV Switch" button to turn on ultraviolet light, which activates the fluorescent dye. This will allow you to view the neuron's anatomy. Different types of neurons have unique shapes, which can be used to identify them.
Click the "Dye Injection" link below to inject a fluorescent dye from the tip of the electrode into the neuron's intracellular space. Click the "UV Switch" link below to turn on ultraviolet light, which activates the fluorescent dye. This will allow you to examine the neuron's anatomy. Different types of neurons have unique shapes, which can be used to identify them.
Select: Dye Injection UV Switch Continue
Identify the Neuron
You now have both electrical and anatomical data on the neuron. Try to identify the neuron's type based on published reference data (Atlas). This ganglion contains many neurons in different locations. Probe and identify as many neurons as you like. Once you are finished, click the "Conclusion" button.
Neuron T (Identified)
Neuron N (Identified)
Neuron P (Identified)
Neuron X (Identified)
Neuron R (Identified)
| No Stimuli | No Response |
| Brush (Weak) | 18 rapid spikes |
| Probe (Medium) | 6 rapid spikes then 1 spike |
| Forceps (Strong) | 6 rapid spikes then 1 spike |
| Dyed Neuron Anatomy | This dyed cell image shows a thick branch extending from right to left across the image. About a dozen short, thin branches branch off the thick branch towards the top. Extending below and almost perpendicular to the thick branch is a solid small bulb on the left and two thick branches on the right. |
| No Stimuli | No Response |
| Brush (Weak) | No Response |
| Probe (Medium) | No Response |
| Forceps (Strong) | No Response |
| Dyed Neuron Anatomy | This dyed cell image shows a thick branch extending from the top to the bottom of the image. Many long, thin branches extend from the left of the thick branch. About halfway down the thick branch, there is a short branch that extends to the right and has a medium-sized solid bulb at the end. |
| No Stimuli | No Response |
| Brush (Weak) | No Response |
| Probe (Medium) | No Response |
| Forceps (Strong) | 5 spikes |
| Dyed Neuron Anatomy | This dyed cell image shows a thick branch extending from right to left across the image, embedded in a nest of long, thin branches that extend towards the top. Extending below and almost perpendicular to the thick branch is a solid medium-sized bulb on the left and two thick branches on the right. |
| No Stimuli | 1 spike repeating |
| Brush (Weak) | 1 spike repeating |
| Probe (Medium) | 1 spike repeating |
| Forceps (Strong) | 1 spike repeating |
| Dyed Neuron Anatomy | This dyed cell image shows a thick branch that extends from the right to a large solid bulb at the center. This branch has about a dozen thin, short branches that extend towards the top, as well as another thick branch that extends perpendicularly towards the bottom. |
| No Stimuli | No Response |
| Brush (Weak) | No Response |
| Probe (Medium) | 7 spikes |
| Forceps (Strong) | 11 spikes |
| Dyed Neuron Anatomy | This dyed cell image shows a thick branch extending from right to left across the image. Many short, thin branches branch off the thick branch towards the top. Extending below and almost perpendicular to the thick branch are two thick branches. Between the two branches is a medium-sized solid bulb, which is attached to the left branch. |
| N Cell | T Cell | P Cell | R Cell | X Cell | |
|---|---|---|---|---|---|
| No Stimuli | No Response | No Response | No Response | 1 spike repeating | No Response |
| Brush (Weak) | No Response | 18 rapid spikes | No Response | 1 spike repeating | No Response |
| Probe (Medium) | No Response | 6 rapid spikes then 1 spike | 7 spikes | 1 spike repeating | No Response |
| Forceps (Strong) | 5 spikes | 6 rapid spikes then 1 spike | 11 spikes | 1 spike repeating | No Response |
| Dyed Neuron Anatomy | N: This dyed cell image shows a thick branch extending from right to left across the image, embedded in a nest of long, thin branches that extend towards the top. Extending below and almost perpendicular to the thick branch is a solid medium-sized bulb on the left and two thick branches on the right. | T: This dyed cell image shows a thick branch extending from right to left across the image. About a dozen short, thin branches branch off the thick branch towards the top. Extending below and almost perpendicular to the thick branch is a solid small bulb on the left and two thick branches on the right. | P: This dyed cell image shows a thick branch extending from right to left across the image. Many short, thin branches branch off the thick branch towards the top. Extending below and almost perpendicular to the thick branch are two thick branches. Between the two branches is a medium-sized solid bulb, which is attached to the left branch. | R: This dyed cell image shows a thick branch that extends from the right to a large solid bulb at the center. This branch has about a dozen thin, short branches that extend towards the top, as well as another thick branch that extends perpendicularly towards the bottom. | X: This dyed cell image shows a thick branch extending from the top to the bottom of the image. Many long, thin branches extend from the left of the thick branch. About halfway down the thick branch, there is a short branch that extends to the right and has a medium-sized solid bulb at the end. |
Congrats!
You have identified all the neurons for this exercise. In reality there are many more neurons that make up the ganglion. Press the "Conclusion" button.