[MUSIC] We're going to talk about neuroanatomy, and there's a lot of detail. There's lots and lots of detail and I have this perverse enjoyment of all that detail. But I think that fir the purposes of introducing you to the beauties of neuroanatomy and of neurobiology. Let's focus on functional neuroanatomy, what are the different parts of the central nervous system do? We already are now familiar and comfortable with this schematic which shows the progression from the spinal cord through the brain stem, diencephalon, and telencephalon. Let's start with how do we get sensory information in from the world? And let's start at the spinal cord, so in the spinal cord, there's only one type of sensory information that comes in and that's somatosensory information. The somatosensory information, again, is touch, pain, temperature, pressure, vibration. And a few things that we're not very conscious of such as where our bodies are in space? How much oxygen there is our blood? And the pressure in our blood vessels things of that sort. So all that information is going to come into the spiral cord and that's the only type of sensory information that comes into this spiral point. In the brain stem, we get a bunch of different information that comes into the brain stem. One is somatosensory from the face, so the somatosensory information that comes into the spinal cord is only from the body, from the face that comes into the pons. We also get hearing and vestibular information into the hind brain, so hearing is obvious. This is coming in from the ears, this allows us to understand most importantly, spoken speech. But vestibular is that sense of how you're moving in the world whether you're falling, whether you're accelerating forward or accelerating back, all of this is a vestibular signal. So that's it, and then into the forebrain there are two things that come in. One is smell and smell comes in directly into the telencephalon. We saw it a little bit in the nerves, where we looked at cranial nerve one that comes in through the cribriform plate, it comes right in to the cerebral cortex. Vision comes right into the diencephalon. Remember that the optic nerve develops as an outpouching of the diencephalon, so that's the sensory input to the nervous system. It's distributed throughout the length of the central nervous system, information coming in. Now, I should say that the spinal cord is not going to help you perceive somatosensory information. It's not going to allow you to perceive, for sensory perception, you have to get to cerebral cortex. All we're talking about here is where information originates, where it comes in through. And the information comes in through either the spinal cord, the hind brain or the fore brain. Okay, what about motor information? Well, for moving our body, once again, this is all spinal cord, so we want to move our arms, our hands, our legs, our feet. That's all information that comes out of the spinal cord. In contrast, the hindbrain has a variety of very important, houses a variety of very important neurons. These are motor neurons that allow you to swallow, to talk, to block off your throat, that's called the gag reflex. And I should add one here, the cough reflex, which allows you to block off your airway. And these are obviously very important speech I guess you could call a luxury. These others are pretty much necessary for life, for survival, I would say speech is pretty important. And in a person that has a problem with speech, that's called dysarthria, that can be very devastating. From the pons, we also get both facial expressions and horizontal gaze. What is horizontal gaze? It means moving your eyes off to the side, okay? So that is organized in enabled by outputs from the ponds and then vertical gaze comes out with the mid brain. So, moving your eyes up and down that is organized and the output come out of the midbrain, and one other eye movement comes out of the midbrain entirely, and that is near vision. So if I look far, my eyes are oriented in this way, but if I look close, if I look at something near to me. My eyes go from being oriented this way to oriented this way, that convergence of my eyes is enabled by the mid brain. So you can start to see that the central nervous system is dividing up the functions. The functions, the sensory functions, the motor functions it's dividing it up across these various parts of the central nervous system. There's one really important thing to remember which is that there's no motor output from the forebrain. So, when we talked about Bobbi, he had a problem, he had a cut somewhere around here, that the problem was that he couldn't direct his muscles only through his forebrain. He had to get to either the brain stem or the spinal cord to direct his muscles, his motor neurons to move his muscles. So that's really interesting, the forebrain has no motor output, it has to get someplace else to direct motor output. Finally, what we're going to look at is the autonomic output as you remember, autonomic output is of two varieties. It is either sympathetic or parasympathetic. The sympathetic outflow comes entirely from the thoracic cord, this is things that aid you in times of great excitement. If you're in a fight, if you're trying to get away from somebody. This enables you to sweat, it enables you to beat your heart faster. It enables you to increase your blood pressure, it does not enable you to do things that promote relaxation, it does not enable you to sleep. On the other hand, let us see if we can change the color here, we have the parasympathetic system which comes out of both the brainstem and the sacral cord. And we call the parasympathetic system for that reason because it's split. We can call it the Craniosacral System, so what's the parasympathetic system? It's the opposite of the sympathetic system, it's promoting relaxation, it's promoting sleep, it's promoting digestion, it's promoting avoiding. It's doing very nice, simple things, or relaxing things. So parasympathetic outflow in the sacral cord is going to the colon, the bladder, and the sex organs. And parasympathetic outflow from the brain stem is going to the body above the colon so most of the body it comes down. It's a bizarre thing but it comes down and innervates a bunch of the digestive track and these are the body and it goes to the eye. So, what's interesting here is that the eye is getting parasympathetic outflow from the midbrain and that tells the eye to constrict, so it constricts the eye, the pupil. And then, the sympathetic system comes out of the thoracic cord and actually goes to the eye from the thoracic cord. That's weird, but true and it tells the eye to dilate. So, if you have a spinal cord injury, what's going to be the problem? The problem is going to be that you don't get information, mass sensory information. You're not going to know what's coming in to your trunk or your legs. Let's say that your cut is here, and you're not going to be able to move your legs. But in addition, you won't dilate your eye, and so you're eye's going to be very, very constricted. It's called miosis, so instead of having a normal pupil, the pupil will be a dot, okay? And in contrast, if the parasympathetic outflow to the eye Is injured in some way will get a dilated eye. So that is all, this is everything, all the outputs of the central nervous system, except for one, and that one is the pituitary. The pituitary is controlled by the diencephalon. The diencephalon in fact was born, it was imagined, it came into evolutionary existence in order to control hormone release. That's the core function of the diencephalon is to control hormone release and so our hypothalamus controls our pituitary gland which releases hormones into the body. So unlike scalar motor output, which is only from brain segment, and the spinal cord. Autonomic motor output, you could say that there is some that comes out of the diencephalon, out of the forebrain and that is hormone release. That is a quick survey of regional functions in the central nervous system. [MUSIC]
