BIOL 3800 1st Edition Lecture 13 Outline of Current Lecture I. Central Nervous SystemA. Spinal Cord and BrainB. Other Important TractsC. Spinal NervesCurrent LectureChapter 8 and 11I. Central Nervous SystemA. Spinal Cord and Brain1. Left right symmetry of spinal cord so that means whatever we look at on spinal cord is also on the other side then we have division into gray and white areas and the only reason for the white areas is that those are the cables.2. The myelinated cables cut in cross section you can see the myelin sheath and it gives you a glistening white appearance that’s where that comes from. 3. If you say in here there is some myelination too there is it’s just not organized the way it is out here where the tracts are consequently it does not look as white it looks gray. 4. There’s always a belly button that’s center of canal cerebral spinal fluid and the cerebral spinal fluid also surrounds the spinal cord there are all kinds of membranes out there but in arachnoid layer you have cerebral spinal fluid there for cushioning. 5. The pia mater means tender mother in Italian and dura mater means the tough mother in Italian and so dura mater is tough connective tissue that protects your spinal cord and also your brain a. The pia mater is a very fine delicate layer of connective tissue sitting right on top of your brain tissue. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.6. If you are in the dorsal root, and the ventral root you have specialized informationthe ventral root motor neurons going out to your muscles and dorsal root those are the unipolar cells it is the peripheral process coming in the kitchen 7. Number 5 is the in this picture is area where you have all of your motor neurons, motor neurons means movement so that means those are the neurons which giverise to the axons that go all the way to your muscles and form the synapse there which uses what as a transmitter? And would it use G proteins?a. Answer: Acetylcholine. b. NO. 8. Number 1 and 2 fasciculus gracilus and fasciculus cuneatus. a. They are both called the dorsal columns. b. The information in there in terms of action potentials give you the sensation of touch from the lower body and in the first one in 1,2, from the upper body division at about belly button. c. All of them have the same function it’s just a matter lower body and upper body. Conscious touch sensation from lower and upper body and also proprioception information meaning what?i. Example: Where is my arm well I can close my eyes and say it is over here, but if you cut some of those fibers you don’t know where your arm is. You have no idea you have to visually locate it proprioception means that you have some idea in space of where your extremities are. 1 2 3 4 5 6 7 8 9 10 11 12Muscles still move and everything is fine just would not have proprioception if those fibers cut. ii. You would also not be able to touch your nose very quickly you would get bloody nose. This is because the spindle apparatus and all that tells you how fast your elbow is rotating, how fast your muscles are contracting, all of that goes up those dorsal columns in form of action potential, no magic. B. Other Important Tracts 1. Dorsal root all sensory, ventral root 10 all motor but in between we have interesting things so let’s take a look at 7. 2. Lateral cortico-spinal tract meaning it starts in the cortex goes to the spinal cord it’s descending it’s motor. So it’s the lateral cortico-spinal tract meaning there is amedial one which we will ignore we only have about 20% of the total tracts there. a. That’s all we need but it is something to hang your head on. So that means whatever information is here, these axons have to come from cells somewhere, you don’t get an axon by itself it dies if its cut away from the cell body 3. So they start in the cortex we will find out where in the cortex and where they are and they go to the spinal cord that means fibers at certain levels will enter the spinal cord interneurons and finally motor neurons and make you do something. 4. As contrast look at number 8 which is the rubrospinal tract. It comes from the red nucleus in the midbrain we haven’t really been insisting on that and that is why it’s called rubrospinal. a. It has more vascularization than other regions it has to do with posture control the fixation of your frame in space. b. So let’s look at an example if you have a pianist and he is playing beautiful music and then somehow you could interfere with the action potential transmission in these axons what would happen? No more movement of the fingers no more movement of the lower arms because the lateral cortico-spinal tract deals with voluntary movements with emphasis on the arms. So that pianist would be sitting there wondering what’s going on but he is pretty much paralyzed in his arms. c. If however you block transmission in number 8 postural control he would be playing and all of a sudden he would melt off his seat, slide off his feet,playing on the way down but then he is on the floor. That means he cannot maintain posture. That is simplified, there are other tracts in there that deal with posture control but the rubrospinal tract is one of the main ones so posture and voluntary precise movements. 5. The body postural control is the rubrospinal tract and a couple of tracts we are not talking about. 6. The hand movement guided by your eyes is mainly information in number 7 which is the lateral corticospinal tract, these numbers are arbitrary in a moment when we get to the cortex we actually have numbers that mean something. So can you see the difference? Can you also see that there is also some kind of specialization? Now this isn’t just going down the all the same pipe.7. Lateral spinal thalamic tract is it sensory or motor? a. Think thalamus in brain …it is sensory… This particular region takes care of all the C fibers that take care of burning pain and also temperature sensation most of them are in this tract and the thalamus is somewhere in your brain which then passes on the information to your cortex. b. So pure C fibers unmylelinated looks gray. Spinal cerebellar tract what is this sensory or motor? Got to be sensory. Going to the cerebellum back here and we don’t know all the things cerebellum does but it gives information to the brain on what body is