Neurophysiology Lab

The Leech

http://www.scientificillustrator.com/illustration/insect/leech.html

In this lab, I will be measuring the resting (0mV) and action potential (-58mV) of a leech neuron. Why leeches? They can't afford lawyers. Actually, the nervous system of the leech is simplified and easier to understand. This will be accomlished by inserting a microelectrode into a single neuron which will enable me to measure electrical changes in the cell. The cell will be stimulated by different items and the response displayed on the oscilloscope. Different neurons will respond differently to the same stimulus.

Here, the oscilloscope demonstrates the cell's response to the microelectrode. The response was the same for the feather, probe and forceps.

Below is the image obtained after injecting Lucifer Yellow and illuminating the results with ultraviolet light.

Based on these results, this is a "R" neuron.

Below is an image of an "N" cell. It's only response was to the pressure of the forceps.

This demonstrates that there are different types of neurons. A sensory neuron gathers information and sends it to the CNS. A motor neuron carries a response which in turn triggers glands or muscles.

Based on this experiment, I would say that leeches do experience pain. Pain is the volley of signals which conveys intensity. The more signalling, the more intense the sensation.

I enjoyed understanding the physiology and observing the responses to different stimuli. I also enjoyed not having to actually touch a leech.

I enjoyed doing this lab. It's very informative and explains each step very well.