02 lecture twocentral nervous systemgross organization.docx

1、02 lecture two central nervous system gross organizationLecture twoCentral Nervous SystemGross OrganizationScope:In this lecture we will discuss the gross or overall organization of the nervous system, and define some important terms and concepts. Here we will be concerned primarily with areas of th

2、e CNS that can be viewed externally; we will be returning to a more detailed discussion of the function of some of these areas and structures in ensuing lectures.OutlineI. Before we can discuss the modern view of brain as the biological substrate of the mind, we need to define some terms that will b

3、e used throughout the course, and to understand something about the gross or overall organization of the brain.A. The term CNS refers specifically to the brain and spinal cord; the brain is continuous with the spinal cord through an opening in the skull (foramen magnum).B. The peripheral nervous sys

4、tem (PNS) consists of neurons and/or nervous located outside of the brain and spinal cord. An example is the sciatic nerve that runs down the back of the leg.II. If we looked at the CNS from the outside, we would see the following parts.A. The spinal cord, which is protected by our bony vertebrae.B.

5、 Part of the brainstem, which is a phylogenetically older area of the brain continuous with the spinal cord.C. The hemisphere; in humans, much of the brainstem is covered by the two cerebral hemispheres.III. There are a number of reference terms that are used to refer to different areas of the brain

6、 and spinal cord, and to the relative position of structure; some of these terms are shown in relation to a drawing of the brain in Figure 2.1.A. The terms rostral (towards the front of “head” end; anterior) and caudal (towards the back or “tail” end; posterior) are used generally to refer to the fr

7、ont and back of the brain, respectively.B. The terms dorsal and ventral are used to refer to the top and bottom (or underside) of the brain.C. The terms medial and lateral are used in reference to the body midline with medial towards, and lateral away from, the midline.IV. The adult brain can be sub

8、divided grossly along a rostral-caudal dimension into five regions (Figure 2.1); how these regions develop will be one of the topics of a future lecture. A. The telencephalon is the rostral-most subdivision of the brain consisting of the two cerebral hemispheres; the telencephalon is the most recent

9、ly evolved area of the brain and its function will be the focus of many lectures in this course exploring the relationship between mind and brain. It is the outer surface of the telencephalon (cortex), which is believed to be the seat of the mind.B. The diencephalon includes the thalamus (anteroom),

10、 an important structure consisting of a number of distinct areas/structures, many of which will project to (e.g., be connected to) the cerebral cortex, and hence the name “anteroom”; the hypothalamus which is “below” the thalamus and also composed of a number of individual areas, is responsible for

11、the central control of homeostasis in the body.C. The mesencephalon or midbrain, lying between the diencephalon and the metencephalon; a number of structures in this part of the brain are involved in reflexes.D. The metencephalon (“between” brain) consists of two major structures, the cerebellum (th

12、e large ball-shaped structure on the base of the brain), and the pons (bridge) which connects the cerebellum to the rest of the brain.E. The myelencephalon (long white marrow structure) is also referred to as the medulla or medulla oblongata, and is so-named because it contains many of the long path

13、ways or tracts (axons or processes of neurons traveling together in a bundle) in the brain, for example, axons projecting to the spinal cord; it is the medulla which is continuous with the spinal cord at the foramen magnum.V. Other general terms are also commonly used to refer to different brain sub

14、divisions.A. The forebrain refers to the rostra-most subdivisions of the brain, and includes the telencephalon and the diencephalon; the forebrain is the most recently evolved area of the brain phylogenetically.B. The hindbrain consists of the caudal brain subdivisions and includes the metencephalon

15、 and the myelencephalon. For example, the medulla would be considered a structure of the hindbrain; the hindbrain is considered a phylogenetically older or more primitive part of the brain, controlling vital, but largely unconscious or subconscious, functions such as breathing and heart rate.C. The

16、brainstem is a collective term used to refer to the mesencephalon, metencephalon, and myelencephalon; like the hindbrain, the brainstem is considered an older area phylogenetically.VI. In the next lecture, we will see that internally, the brain is also organized into different areas. Future Reading:

17、Any recent neuroscience text will cover most of the basic information covered in this lecture, although in much greater detail. The authoritative book in neuroscience is Principles of Neural science, edited by E. R. Kandel, J. H. Schwartz, and T. M. Jessell.Questions to Consider:1. What are the five

18、 subdivisions of the adult human brain from rostral to caudal? Why do you think the telencephalon is so large in humans?2. Sometimes the meaning of a name gives a clue to its function. Why is the thalamus the anteroom?Lecture TwoTranscriptCentral Nervous SystemGross OrganizationWelcome back. In our

19、introductory lecture, it was stated that the modern view is that cognition and perception are the result of the brain processes. The truth is that every single thing you can hear, feel, see, every thought you think, is the result of the brain processes. But before we can get into talking about some

20、of these topics, we need to define some important terms so we are all on the same page about how we use language. And we need to understand some very basic principles about how the brain is organized. So the next few lectures are going to provide that foundation material on which the rest of the cou

21、rse is going to be based. The terms, definitions, and other things we will talk about and learn in the first part of the course are going to be important for understand all of the other lectures.In this specific lecture what we want to do is talk about the “gross organization of the brain,” and the

22、term in neuroscience is used to mean the external features of the brain, what can be seen without the aid of a microscope. So when we talk about the gross organization, its the overall big, large organization of the brain.We are going to return to a discussion of function of individual areas at a la

23、ter time, but here we are going to learn some definitions and terms so that we all know where we are when we talk about the brain.So, lets start with some of those basic definitions. The term “central nervous system” refers to the brain and the spinal cord. The brain is continuous with the spinal co

24、rd through a hole in the skull, which is called the foramen magnum. You all know that your spinal cord is in fact protected by bony vertebra and that your brain is in this compartment here. And the brain and spinal cord have to be continuous, so there is a hole in the bottom of the skull. And this i

25、s where the brain and the spinal cord are continuous.This course is going to focus primarily on the brain, so on that part of the central nervous system. But there is another part of the nervous system that we arent going to cover in this course, and thats called the peripheral nervous system.The pe

26、ripheral nervous system is actually an ante-neural element that lies outside of the brain and spinal cord. So the peripheral nervous system would be, for example, you have a long nerve called the “sciatic nerve” that runs down the back of the legthis is part of the peripheral nervous system. Any par

27、t of a nervous structure, whether its a nerve cell or a process of a nerve cell, which lies outside of the brain and spinal cord, would be part of the peripheral nervous system.Now, throughout this course we are going to be using what I call the handy dandy brain model. This beautiful model with all

28、 of these different colorsyou turn it like this, you can see it from different sidesthe one in your head is actually much more beautiful than that, but this is the only model that I had. We are going to be using this when we point out different areas of the brain, so its important that you be able t

29、o immediately orient to this model.Now, just like we have two sides to the body, we have a right and left side to our body, we have two hemispheres in our brain. This model is only one hemisphere so its used for teaching purposes. The other hemisphere, which would be located here, is not shown. What

30、 we want to know is where the front and the back of the brain are, so whenever I talk about something and refer to this model then you can look at it and youll know where we are.This is the front of the brain and this is back of the brain. And one of the ways you can always know that this is the bac

31、k of the brain is to orient to this little structure right here. This little fist-shaped structure is called the cerebellum and its going to be a topic of one of the lectures later on. But the cerebellum is here at the base of the skull and so you can always tell where the back of the brain is.The o

32、ther thing I want you to notice with this model is that this is a right hemisphere. So this is the front, this is the back. And that would make this a right hemisphere of the brain. So when we talk about these different structures and I point things out on this model, then youll know basically where you are at.Now we have looked at the central nervous system from the outside; so we imagine that this was our brain and we are going to look at it from the outside. If we look down here, we would see the spinal cord. So again, the spinal cord is part of the central nervous system, and it is p