An answer to a question such as that greatly depends upon the individual you’re asking. To some, leeches are just another component in the great Circle of Life (thank you Elton John for making that phrase forever associated with the phrase “Aaaaaashawaynaaaaa”). To others, particularly young girls, they are slimy, disgusting, genuinely gross creatures that can never be far enough away. And yes, that hurts the feelings of leeches. I mean, how would you like to be called gross? It’s emotionally scarring, I’m sure! However, this blog post isn’t about the emotional problems of the common leech (though that probably hurt their feelings as well). Regardless, this post is about a virtual lab on the internet that is created by the Howard Hughes Medical Institute. The purpose of this project is to simulate an experiment involving nerve cells within leeches. This step by step virtual lab provides an understanding of how to measure nerve impulses, how these nerve impulses vary under different conditions, and provides basic information as to how nerves are identified. Shall we get started?
You might be wondering, out of all the creatures of the Earth, why a lab (especially a virtual lab) would use leeches as a dissection subject? As you are about to see, this virtual lab strives to be as accurate as possible. Leeches are the most practical choice for a science lab because they are relatively small, come in great supply, and are genuinely easy to tolerate (they don’t require a daily walk around the block, a refill of kitty litter, or even a changing of newspaper!). Furthermore, they have relatively simple nervous systems. These systems are similar to that of a human nervous system. They are easy to understand as a whole, and what is learned by them can easily be applied to the human body.
The virtual lab is located here. Feel free to do this lab yourself, and use this post as a supplement along the way. It will help in your understanding of this post by having knowledge of the lab itself (or visa versa). Shall we get started?
This lab requires a laundry list of materials. The purpose of each material, some are more self-explanatory than others, will become clear throughout the process of the lab. The list is:
- Leech Tank (with Leech of course)
- Leech Tongs
- Dissection Tray
- Dissection Pins
- Feather (weren’t expecting this one, were you?)
- Dissection Microscope
- Micromanuoulator (pronunciation not included)
- Solution of 20% ethanol
The lab that you will find online goes through each individual step of this dissection. This includes things such as grabbing the leech and stretching the leech on the tray (like I said, the lab is very realistic). The following steps that I provide are more condensed and general. To get the full effect of what is happening, please do the lab yourself!
(Note- the link is above. Below is just the starting screen of the lab. You cannot click the picture to go to the lab).
Step 1: Take the leech, and anesthetize it with the 20% ethanol solution. Lay the leech on the dissection tray (dorsal side up) and pin it with dissection pins.
Step 2: Use scissors to cut open the leech, and forceps to open the incision. Remove the internal organs to expose the nerve cord (which is on the ventral side).
Step 3: Under the dissection microscope, identify the sinus and cut a window around a ganglion. The Sinus of a leech is a component of the leech’s circulatory system (you see, leeches have their nervous system within their blood vessels). A ganglion is a collection of neuron cell bodies. These ganglia are apparent in this step of the lab.
Step 4: Cut the leech into sections, so only a body section with the area from step 3 remains. Then flip the body section over, and cut the sinus (this should reveal the ganglion).
Step 5: Use the micromanuoulator. This is an electrode that can be inserted into individual neurons. The oscilloscope monitor is also visible, and shows the impulses that is being created by that neuron. (The virtual lab comes equipped with multiple neurons. So each one may have a different impulse visual, based on where you inserted the electrode).
Staying true to the real structures of lab procedures, I decided to make a hypothesis of what I was about to find. My thoughts were: If I alter the type of stimuli given to an exposed neuron within a leech, then I will be able to identify the type of neuron, because each neuron picks up different signals from the body- each one specific to a type of stimuli.
Step 6: Use different stimuli to check the responses of the neuron. The feather represents a light touch, the probe a medium touch, and the forceps a strong touch.
Step 7: At the same time as step 6, you can also inject a fluorescent dye (known as Lucifer Yellow, as it turns bright yellow-green under UV light) into the neuron. By hitting the Ultra Violet switch, you can see the cell body (the studying of the form and structure of an organism and its parts, such as this, is known as morphology by the way).
Step 8: Use the data table (seen below), and the research you collected, to identify the type of cell you found. Take special notice how each cell, determined by a letter, responds differently to different stimuli. Repeat steps 5-8 to your hearts content!
As far as statistical data, there is not a lot of information to be retrieved from this lab (the majority of what was discovered was from observations). However, there is still a lot of information and knowledge that can be gained. First and foremost, this entire lab is about doing what is referred to as “electrophysiology”, or more commonly called “neurophysiology”. These terms are defined as “the study of life processes and of the physical and chemical processes involved, particularly the electrical aspects”. By doing such a procedure, it is possible to see how different neurons react to different conditions. It can be concluded that each neuron reacts differently, and looks different for that matter, because each one is responsible for detecting a specific stimuli. It can also be concluded that these specific impulses can be used to identify what type of neuron is being observed. Lastly, a lab like this can show how neurons work in general, as well as the steps scientists undergo to observe such a process.
That about does it for this blog post. Looking back, we have really been quite productive! We have identified the purpose and materials required to dissect a leech, gone through each step of that dissection, and then analyzed our results and what it means to the overall study of the nervous system. And as a final note, it is important to say that no leeches were harmed in the making of this blog post or the lab…at least, not physically anyway!