Leech Neurophysiology Lab

Neurophysiology Lab


Purpose: To observe electrical activity in a Leech neuron.



Hypothesis: My hypothesis is that the electrical activity in a leech neuron is going to be really high, just because of what they are capable of doing.

Materials: The materials include: Feather, probe, forceps, scissors, pins, scalpel, dissection tray, leech tank, 20% Ethanol, leech tongs, dissection microscope, micromanipulator, oscilloscope, and a leech.


Procedure:
              Step 1) Catch and anesthetize the leech in 20% ethanol solution.

              Step 2) Pin the animal dorsal side up through the anterior and posterior suckers onto a dissection tray, stretching the animal in the process.

              Step 3)Then get the scissors, make a cut in the skin along the mid-line of the dorsal surface, but not to deep so won't damage anything in the inside of the leech. Secondly, you get the forceps and carefully tease apart the skin along the cut, then pin down the left and right halves of the skin to each side, so that the leech is pinned open with the inside of the skin facing up. This will then uncover the innards of the leech, including the digestive, excretory and reproductive organs. You will not yet see the nervous system.

              Step 4) Carefully remove the gut and other internal structures to see the ventrally located nerve cord. The nervous system of the leech is encased within the ventral sinus, which is the dark green color.

             Step 5) Notice that there are many swellings up and down the sinus. These contain the segmental ganglia of the nervous system. To make one of them accessible, first we cut a window in the body wall underneath a ganglion, taking care not to damage the nerve cord or any attached nerve in the process.

             Step 6) Isolate a section of the animal by making two parallel cuts across the animal, but sufficiently separated  so that the strip you remove contains at least one ganglion.
Then with the forceps flip the piece of the skin over so that the outer skin is now face up. Pin the skin down.
             Step 7) Cut the sinus with an ultra fine scapel and using fine forceps, carefully tease apart the sinus to expose the ganglion. Individual cells can now be viewed under the microscope.
           
            Step 8) Now using a feather, probe, or forceps, push around the skin of the animal. Observe if the cell you have penetrated responds to weak (feather), medium (probe), strong (forceps), or any stimulus. Note the pattern of the response. The cell may fire action potentials or spikes. The response characteristics will be used when you are comparing your data with published data complied int he atlas. When you are satisfied with the electrophysiology, you can start the anatomical investigation by injecting the cell with a fluorescent dye. Push the button labeled "Dye Injection."
          
          Step 9) Next, we will visualize the morphology of the neuron from which you have just recorded using a fluorescent dye. having pushed the button labeled "dye injection" the amplifier system has passed an electric current from electrode that resulted in the ejection of the lucifer yellow from he tip of the electrode into the intracellular space. Lucifer yellow will passively spread throughout the cell after a while. Now you can turn on UV light by pushing "UV switch". Lucifer yellow fluouoresces bright yellow-green under UV and you will be able to visualize the cell.     



Results: The results that I have gotten from this lab is that in order to find out what exactly is going on with the leech and how their whole neuron system, you have to go in and take everything out and like actually test out their sinus and ganglion, so on and so forth. So it was really neat how you would have to do that!
Conclusions: Only some cells were sensory to some items and not all. They  can only effect some part of the leech's body in order to effect it!

The Chewing Lab

Click on lab to see our chewing lab and data.
Lab

Mouse Article (:

          This article was about a man who wanted to take science further than just letting stuff sit over night and grown in a dish, so he decided to go on and experiment with a cartilage and a mouse. And he started with nutrients and waste removals. Since the scaffolding can be molded into any shape or size, they decide to shape it as an ear.

           So after they had shaped it an what not the tissue was then seeded the scaffold with little cartilage cells and then that implanted the mold under the skin. They did this through surgery.The way this worked is the hairless mouse was specially bred to lack in immune system that might reject the human tissue, nourishes the ear as the cartilage cells grow.So as time passed the ear grew successfully on the hairless mouse.So with that said they ear was removed from the mouse and the mouse lived healthier then ever.

http://www.pbs.org/saf/1107/features/body.htm

Homeostasis

 Homeostasis is something that tried to keep the body at all the same temperature.

It shouldn’t vary in many temps at all. A great example of this is, say you were on a beach trying to get a nice tan! Once you start getting the tan you just lay there and decide to tan more. Well once you start over tanning your body gets really hot and starts to sweat. When the body sweats it is giving negative feedback.It is giving negative feedback because the body temp goes up and then back down.The reason for the sweat is that your body is trying to cool itself down because it is used to it being at one temperature. So then again homeostasis is a big part of the body just trying to keep it all at one steady temp!!

The Simple Squamous Epithelium, is a single layer of flattened cells that allows passage of materials by diffusion and filtration in sites where protection is not important.Some examples of a squamous epithelium are: Kidney glomeruli; air sacs of lungs; lining of heart, and blood vessels and many more.

Simple Columnar Epithelium, single layer of tall cells, with round to oval nuclei; some cells bear cilia; layer may contain mucus-secreting unicellular glands. Absorption; secretion of mucus. enzymes and other substances;ciliated type proples mucus by ciliary action.Location: nonciliated type lines most of the digestive tract, gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus.

Simple Cuboidal Epithelium, single layer of cube-like cells with large spherical central nuclei. Two characteristics are secretion and absorption. Examples: Kidney tubules; ducts and secretory portions of small glands; ovary surface.




Pseudostratified Columnar Epithelium,a single layer of cells with different heights; some do not reach the free surface.Function,secretion, particularly of mucus; propulsion of mucus by ciliary action.Present in the male sperm-carrying ducts (nonciliated) and trachea (ciliated).












Stratified Squamous Epithelium,thick membrane composed of several layers of cells. Function in protection of underlying areas subjected to abrasion.It forms the external part of the skin's epidermis (keratinized cells), and linings of the esophagus, mouth, and vagina (nonkeratinized cells).








Stratified Cubodial Epithelium,typically two cell layers thick.It is quite rare in the body.Found in some sweat and mammary glands.






Stratified Columnar Epithelium,limited distribution in the body. Found in the pharynx, male urethra, and lining some glandular ducts. Also occurs at transition areas between two other types of epithelia.









Transitional Epithelium,several cell layers, basal cells are cubodial, surface cells are dome shaped. Stretches to permit the distention of the urinary bladder. Lines the urinary bladder, ureters, and part of the urethra.

Levels of Structural Organization