Tuesday, July 1, 2008

Unit 3, Online Lab #1: Leech Neurons

Screen shot of the manipulator with the oscillope trace:

Ultra-violet image of the neuron with dye in it showing it has the shape of a sensory neuron:

1. What is the electrode measuring?
The electrode is measuring voltage. When combined with the measurement of the reference electrode, you are making a measurement of the membrane potential (potential difference across the neuron's membrane).

2. Why use leeches in neurophysiology experiments?
The leech is used because it has a simple nervous sytem. Simple systems are easier to understand. What is learned from a simple system can be applied to more complex systems, because simple nervous systems obey many of the same rules as complex ones. We can use what we learn about the leech's nervous sytem to help us understand more about our own brain. Their neurons are large which make them (relatively) easy to penetrate.

3. What is the difference between a sensory and a motor neuron?
A sensory neuron transmits nerve impulses to the CNS after it's sensory receptor (exteroceptor or interoceptor) has been stimulated by either the external environment or internal enviroment. A motor neuron transmits nerve impulses away from the CNS to an effector (muscle fiber or gland).

4. Do you think a leech experiences pain? What is pain?
This was a tough question. My initial reaction is to say no. Because they are much simpler beings, it's hard to imagine that they can feel pain. I think what makes it difficult to comprehend is that humans tie emotions to pain. But when strictly looking at the definition of pain, yes, I think leeches experience pain.

Pain is a sensation that is induced by a stimulus which is derived from damaged tissue. It is characterized by physical discomfort.

5. What were the two most interesting things about doing this lab?
I liked learning about the method and equipment used to measure membrane potential of neurons. I also liked the way the listed each specific tool, what it's used for, and how much it can cost.

6. Anything you found confusing or didn't like about the lab?
Once or twice I wanted to go back to find something I had previously read and had a little difficulty finding it. Other than that I really liked this lab.

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