Hypothesis:
The purpose of this lab is to observe the electrical activities of neurons while stimulus is delivered. I believe that the electrical activities of a single neuron will be affected more by a stronger stimuli versus a weaker stimuli.
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Materials:
- Feather
- Probe
- Forceps
- Scissors
- Pins
- Scalpel
- Dissection Tray
- Leech Tank
- 20% Ethanol
- Leech Tongs
- Dissection Microscope
- Micromanipulator
- Oscilloscope
- Leech
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Procedure:
- Use the leech tongs to place the leech in 20% ethanol solution to anesthetize it.
- Pin the leech dorsal side up through the anterior and posterior suckers onto the dissection try.
- Use the scissors to make a cut in the skin. Cut along the mid-line on the dorsal surface. Make sure not to damage deep structures.
- Use forceps to carefully pull the skin along the cut and pin down the left and right halves of the skin to each side. This way the leech is pinned open, and its innards are exposed.
- Carefully remove the internal organs in order to expose the nervous system.
- Us the scalpel to make two parallel cuts across the animal. Make sure the removed strip contains a ganglion. Use the forceps to flip the skin over, and pin it so that the outer skin in facing upwards.
- With a very fine scalpel cut the sinus, and using the forceps move the sinus until the ganglion is exposed. You will now be able to see individual cells under a microscope.
- Move the electrode over the ganglion to stimulate the process of penetrating a cell. Keep moving the electrode until you find a cell.
- Use the feather (probe or forceps work as well) to push around the skin of the leech. Check if the penetrated cell responds to weak (feather), medium (probe), or strong (forceps) stimulus.
- Begin your anatomical investigation. Inject the cell with a fluorescent dye. Now that the cell is dyed, click the UV switch in order to see the dyed cell in UV light. You can now identify the cell by using the Atlas.
Results:
There were five different types of cells found, and each of them reacted differently to different stimuli. The Atlas for the lab shows all the different ways each cell reacted to the different stimuli:
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Conclusions: Overall, no one stimuli caused the most electrical activity in all five cells. There were cases, such as the N cell, where the strongest stimuli was the only cause for electrical activity. However, in other cells, like the T cell, the weakest stimuli caused the greatest activity. Overall, all the cell types, with one exception, showed some type of activity when one type of stimuli was delivered.
