13. The Peripheral Nervous System
Organization of Sensory Pathways
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Okay. So in this video we're going to be talking about the circuit and the perceptual levels. Now the circuit level pretty much consists of impulses that are being delivered to the appropriate region of the cerebral cortex. So this is basically those action potentials that we talked about actually getting up, going up those ascending pathways toward the brain. So I always think of this as, like, you know, in cartoons when characters make little phones out of tin cans and they're, like, connected by a string? I always imagine we have, like, the sense receptors holding 1 tin can and the brain is holding the other one and that little string is basically the circuit level. It's the actual circuitry that that connects them. And these ascending pathways, or the circuitry, consists of neurons. Now the number of neurons can differ. On average, it's about 3, but there can be fewer than 3, so just keep that in mind. So once this signal actually gets up to the brain, we have the perceptual level. So at this level, the sensory input is processed and interpreted by the cortex. So here we're going to have our conscious awareness of the stimulus including all types of information such as the location of the stimulus, the intensity of the stimulus. So you know, are these lights very bright? Is this food very flavorful? Information like that. And then pretty much any other properties of the stimulus. So here we're gonna start to understand the more kind of fine tuned detailed information. So if we're thinking about touch this might be more detailed textural information. So, like, wool is soft and kind of scratchy. If it's food, we're getting kind of more fine tune understandings of the flavors. My tea is bitter. It's also sweet. So all of that detailed information kind of reaches our conscious level. So to give you a further example we have this little cartoon here depicting the circuit level over here. So she put her foot into her boot and, unfortunately, there is a little spider, although he's a very cute little spider to be fair. And but he's hanging out in her boot and so she had that information coming in from her toe, and it triggered this action potential that get sent up these ascending pathways to her brain. And then she has this perceptual understanding of, oh my gosh, there's a spider in my boot, which poor thing. That's, like, my worst nightmare. Hopefully, she handles it better than I would. But so, yeah, that is the general organization of our sensory pathways from the moment that we detect a stimulus and our receptor responds right up to when we have conscious perception of it. And now that we understand that a little better, we are gonna dive into sensory receptors in some more detail in our next video. So I will see you there.
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