The topic of neuron signals, how they are created and what is their role in behavior is definetely worth spending a lot of time on. In all the previous biology classes that I had, I was never really told WHAT EXACTLY CREATES AN ACTION P0TENTIAL AND HOW DOES IT MOVE ALONG THE AXON. And that's a shame because understanding these concepts really helps me to understand why one reacts to some things in one way and to others in the other way, and why in other cases one would respond in the same way to the same stimuli. This concept also helps to eliminate the confusion as to what can account for the autonomy of the nervous system, and the topic also helps to uncover some of the "magic" that is hidden behind the concept of behavior.
As it was said in lecture, all of the signals passed from different inputs whether they are visual inputs or oliphactory, or audible, are sent along the conceptually-same pathway: by a chain of neurons. Inside the neurons the signals are transmitted in a form of the membrane permeability changes. How then does the organism distinguish between all the different inputs that are sent to it? I would guess, that the route that the signal came from and the final destination of the signal play a crutial role in this matter. For example, it was mentioned in lecture that there are twelve cranial nerves in the human brain, each of which is responsible for the different functions. Could it be that the signal that was received by one of the nerves (for example, the olfactory nerve) follows a special pathway different from the signals that are received by the others, and by the place where it arrives (i.e. by the way it arrives: special neurotransmitters used at the synapse, special receptors, etc.) an organism is able to distinguish between the different signals. On the other hand, it is probably true that if one would stimulate the "wrong" sensory neurons, the signal that would come will not depend on the input as much as on the neuron it came from. For example, if one person would sit with his arm stretched out in front of him, and somebody else would very slow touch his arm from the wrist to the crook of his arm, there will be two completely different responses dependent on the pathway the signal would come in from. Let's say that the first person watches the movement of the other person's hand. In this case, the person will know exactly the time when the other person's hand reaches the crook of his arm: notice, that the person will know because the signal primarily come from his eyes' neurons. Now, imagine, that the first person turned away, while the other person SLOWLY moves his hand across the first person's arm. Then, being asked to tell, when the other person's hand reaches the inside of the elbow, the person will invariably respond about 2-5cm before the inside of the elbow is reached. This experiment shows that the response to a specific stimulus depends primarily on the route it reaches the person's nervous system as opposed to the stimulus itself.
The membrane permeability changes and the passive flow aslo help to account for the autonomy of the nervous system. Such a theory can explain how some signals can originate without any obvious input into the nervous system. This autonomy could probably be used to help to explain the behaviors that are established by human personality (i.e. creativity, sense of humor, thought process, etc.)
Glad you think it worth the time, and intrigued by your additional thoughts. Yes, as we talked about today, similar action potentials/different experiences because in different neurons. And yes, route can make a difference for experience of one thing (I think I'm understanding your point correctly). Certainly the time the inside of the elbow is touched might appear to be different if based on information from eye as opposed to information in cutaneous nerve (though I don't quite see why a "5 cm" difference). To make the situation even more interesting, under normal circumstances one gets both kinds of reports (optic and cutaneous nerve). And if they separately lead to different sense of when something happened, what happens when they are both there? PG