Neurophysiology Leech Lab

Leech opened
for dissection

The objective of this virtual neurophysiology lab was to record the electrical activity of individual neurons when mechanical stimulus is delivered through the skin of the leech. The we injected a fluorescent dye, called Lucifer Yellow, into the neurons the visualize their morphology.The cell was loacted  We identified the neurons based on their response to stimuli. First, we anesthetize the leeches so they won't move (not that they actually would in a virtual lab) and cut them open down the length of the leech. Then we carefully pinned the little guy down exposing its guts and connective tissue inward parts, we removed these parts, leaving the skin. The leech was put under the microscope and a segment was cut out to see the ganglia. Then we cut the sinus and used an electrode to locate a cell. A feather, probe and forceps were rubbed against the cell and the reaction (action potential) was measured. The three stimuli acted as light, medium, and strong stimuli. Lastly, we injected the fluorescent dye and viewed it under the UV light. With the UV light, the cell body, axons, and dendrites were visible.
The way that the cell reacted to the different stimuli demonstrated how there are different ways cells respond to levels of stimuli (light, medium, strong). The neurons can react differently because of their specific function or because of their environment. For example, neurons on your hand will react differently to neurons on your legs or face. Neuron classes are determined by their reaction to various stimuli.

Leech image from http://faculty.baruch.cuny.edu/jwahlert/bio1003/annelida.html
Giant Leeches image from http://philosophyofscienceportal.blogspot.com/2011_10_01_archive.html