Introduction to the Anatomy of the Brain Itself – 105

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Gordon Johnson:        As we begin talking about brain anatomy, I want to talk with just some real big picture topics and then we’ll move from the larger divisions of the brain into more specifics. The brain is essentially divided into the brain stem, the cerebellum, and I may say it wrong, the disencephelon.

Dr. Erin Bigler:            Diencephalon.

Gordon Johnson:        Diencephalon and the cerebrum, is that right?

Dr. Erin Bigler:            Those are the basic areas. The brain stem also will be very important in discussing the coma. The brain stem has an upper part of the brain stem which is called the midbrain and then the lower part of the brain stem is the ponds and the medulla and then on the back of the brain stem is the cerebellum.

Gordon Johnson:        Can we begin by just showing those four basic subdivisions and then we’ll talk about within those subdivisions?

Dr. Erin Bigler:            Certainly and I have a variety of models that I’d like to use in showing that.

Gordon Johnson:        What would be the best way to start, with just showing the basic concepts of what the brain stem and the cerebellum and the Diencephalon –

Dr. Erin Bigler:            Diencephalon.

Gordon Johnson:        Diencephalon, we’ll get it right eventually and the cerebrum.

Dr. Erin Bigler:            Yes and I’ll use what’s called a midsaggital cut to show that.

Gordon Johnson:        You have some tools for us to do that?

Dr. Erin Bigler:            I do. We’ll start with this brain right here, uh, this brain model and I’m going to rotate it here. This is like the brain has been cut in half and so this is very much like my right hemisphere here. So I’m just pulling this out, then I’m turning this around so we can look at this surface right here. This is the brain stem and this is the lower part of the brain stem, the medulla. This is the pons and this is the upper part of the brain stem called the midbrain and this is the cerebellum. This area here is the diencephalon. That is the thalamus and the hypothalamus and then we enter into the telencephalon or the cerebral cortical areas.

Dr. Erin Bigler: We have corpus callosum which connects the two hemispheres and then we have the different lobes. So, on this surface this is the occipital, parietal, frontal and then when I turn it in this way, we see the temporal lobe. We see the cerebellum down here and if I orient it back this way, here is the occipital, parietal and frontal.

Dr. Erin Bigler:   A very important thing that I want to show here is that the adult human brain is about 3 pounds, but look at the size of my thumb and look at the size of the brain stem. It’s about the size of your thumb and so you have the weighty hemispheres sitting on something that’s as small as your thumb.

Dr. Erin Bigler:   Right at this upper area here in the midbrain is a system of neurons that project up into the cerebral cortex called the reticular activating system and the reticular activating system is really the seat of consciousness and it is projecting up into the hemispheres. It also projects into the thalamus and there is another aspect of the thalamus that’s called the diffuse thalamic projection system that’s also related to consciousness. Now the movement of the brain in the skull is often what leads to loss of consciousness and if you stretch this area here in the upper midbrain, you will have an alteration in level of consciousness.

Gordon Johnson:        Okay, doctor, we covered almost our entire course there in the first three minutes. And let me try to break it out a little bit as they say on the stand of I asked you a narrative question and I didn’t get you focused. I guess this would be this side of my brain.

Dr. Erin Bigler:            Yes.

Gordon Johnson:        The brain stem is this some like area down here.

Dr. Erin Bigler:            It, it goes all the way up to right there.

Gordon Johnson:        Now, this area in here is?

Dr. Erin Bigler:            This area up in here, this is cerebral cortex.

Gordon Johnson:        And the dien, diencephalon?

Dr. Erin Bigler:            The diencephalon is this darker brownish area that’s depicted in this.

Gordon Johnson:        And the cerebellum is this.

Dr. Erin Bigler:            Yes.

Gordon Johnson:        Almost separate structure in the back.

Dr. Erin Bigler:            It is a separate structure. It’s actually called the little brain.

Gordon Johnson:        Those are the four basic divisions of, of the brain itself and there are many subdivisions within that?

Dr. Erin Bigler:            Right, there are, there are many other divisions that could be given.

Gordon Johnson:        Okay. And we’re going to come back and talk in particular about the cerebrum and, and the specifics of the way in which the white matter and the gray matter work in some detail.




Gordon Johnson

Attorney Gordon Johnson is one of the nations leading brain injury advocates. He is Past-Chair of the TBILG, a national group of more than 150 brain injury advocates. He has spoken at numerous brain injury seminars and is the author of some of the most read brain injury web pages on the internet.

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