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Phsiology 107 Lecture 3 Part 3.pdf - ● ● In the third part...

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In the third part of lecture three, we're going to begin our survey through the centralnervous system. In this class, we start by looking at the cerebral cortex first. And afterwe do that, we will move into other areas within the brain. And following that, we'll have alook at the brainstem and what some of the structures are in the brain stem. And finally,we'll move to the spinal cord and look at the spinal cord and look at the connections thatconnect the cortex and the brainstem and the spinal cord. At that point, we will move outto the peripheral nervous system and we will specifically look at the autonomic nervoussystem and the cranial nerves.Now today we're going to start by looking at the cerebral cortex. The cerebral cortex isobviously the most important and the best developed part of our central nervous systemand the most different between other species. The cortex itself is about 80% of theweight of the cerebral hemispheres. So it is very large and you'll notice in the lab that it'svery envuluted.One thing that's unique is that the cerebral cortex of humans in almost every area hassix cellular layers of gray matter. They are organized and numbered by Romannumerals. You see here on the left.Layer one has very few cells in it, but is fill full of axons, which you can't see inthis Golgi image. It is also right below the pia mater.Layers 2, 4, and 6 contain primarily cortical interneurons.Layers 3 and 5, contain the larger projection neurons. In layer five we have somevery large projection neurons. And it is known that these neurons project to boththe spinal cord and to the brain stem.At this point in your handout, I've written efferent neurons and afferent neurons. Now Iintroduce those two terms related to the relationship between the central nervous systemand the peripheral nervous system.But they also can be used to describe neurons that project long distances withinthe central nervous system.So I have listed three different types of efferent neurons that have their axons leaving thecerebral cortex. Now pathways. And we're going to be spending a fair amount of time
looking at different pathways in the nervous system that are named by where their cellbody is and where their axon terminal or synapse is.So listed under efferent neurons we have the corticospinal pathway. That meansthese cells in the cortex project to different areas of the spinal cord.We have corticobulbar connections. Bulbar means brainstem. And so those areneurons that project cell bodies in the cortex, terminations in the brainstem.And we also have many, many corticocortical connections. So these areconnections between the right and the left cerebral cortex, and connectionsbetween different lobes in the same hemisphere. So the cerebral cortex, so thoseare the efferent connections of the cerebral cortex that we will be looking at.

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