A number of brain structures are listed below. If an area is primarily gray matter, write a in the answer blank; if mostly white matter, respond with b.  ________    (1) cerebral cortex  ________    (2) corpus callosum and corona radiata  ________    (3) red nucleus  ________    (4) medial and lateral nuclear groups  ________    (5) medial lemniscus  ________    (6) cranial nerve nuclei  ________    (7) spinothalamic tract  ________    (8) fornix  ________    (9) cingulate and precentral gyri

Video transcript

Welcome back, everyone. Here's our next problem in the following regions of the brain mention which ones have mostly gray matter and which have mostly white matter. And we have a list of eight different brain regions that will categorize by their majority composition, gray or white matter. So before I walk my way through the different specific structures, it is helpful to think about the distinction between gray matter and white matter and what each one tends to do to help us think through with each structure. So gray matter has that color because it is made up of the cell bodies of neural cells. And this is where information is processed. Information is taken in in general through the dendrites and the various processes of the cell happening inside that body of the cell. White matter gets its color because the white matter is generally made up of axons and the myelin sheath on the ax axons lips is white in color. And as we recall, axons are what carry the action potentials. So the axons are used to send out messages from the neuro neural cells. So messages out from the cells as opposed to the gray matter where messages are being received and processed in the cell. So that's the general distinction. So we'll keep that in mind as we work our way through these different brain regions. Number one is the frontal lobe. Well, we recall that the frontal lobe is the location of many higher order functions, learning memory, that sort of thing. So it makes sense. The frontal lobe is majority gray matter. I'm gonna put a G or A W. So I don't have little tiny letters filling in the space. Uh because again, mostly uh processing of information there. Number two is the corpus colossal. The corpus colossal is that bundle of nerve fibers connecting the hemispheres of the brain. So we think of that as that information highway communicating between the hemispheres. So it makes sense that the corpus colossal is mostly w for white matter because it's carrying messages from one part of the brain to the other. Number three is the hippocampus. The hippocampus is part of the frontal lobe and is part of the processes of learning and memory. And so it's a pretty easy guess that it's mostly gray matter. Now we move on to number four, the corona rata. Well, this is a group of nerves that sends and receives messages between brain regions. And that might be a little tricky because it is receiving information, but it's sending messages just in the sort of local area of other brain regions. So all the axons are gonna be right there as well. This is as distinct from areas where you might have axons going on down the spinal cord, for instance, going far away in the body. So you might see mostly gray matter. In this case, the axons are running in the area right there. And indeed, the corona rata is mostly white matter. So we'll put a w there. Now we're on to the hypothalamus, hypothalamus is that region that produces hormones to maintain homeostasis in the body. So it helps maintain temperature, help maintains heart rate, controls, hunger signals. So the hypothalamus is receiving information from the body about these statuses and sending out messages, but not by means of action potentials. It's sending out the chemical messengers, the hormones. So the hypothalamus, as we would suspect is mostly gray matter. Number six is basal ganglia. Now, this one I think is a bit tricky. The basal ganglia are involved in motor control and motor learning things like muscle memory. It involves making helping to make decisions about movement. So kind of filtering out sensory information, ignoring extraneous messages. So we might think that axons are going to be involved because we have motor messages being sent out. But let's recall that those messages are being sent to distant parts of the body to control those motor movements. So they do have axons, but the axons are generally going down the spinal cord and the basal ganglia in the brain are primarily gray matter, that one was a little bit tricky. Number seven is the cerebellum and this will be somewhat similar to the basal ganglia. They are also involved in some motor control, but a little more specifically in things like balance coordination proo section, kind of sending out this fine tuning to keep the motor movements uh as they should be smooth and coordinated. And in this case, the overall uh kind of appearance of the cerebellum is gray, the it does have white matter, but the white matter is actually located deeper inside the cerebellum. So the outer surface looks gray but was also a little bit tricky. And then finally, we're on to our last one, the medial lemniscus and this is a bundle of myelinated axons that ascends from the medulla to the thalamus in the brain. It carries information, sensory information of sensations of fine touch, vibration and proprioception. And this one's a pretty easy guess if we remember that it is essentially a bundle of axons. So that would make it wiped matter primarily. So again, let's kind of go through these real quickly. The frontal lobe gray, the corpus callosum white, the hippocampus gray corona, rata, white, hypothalamus, gray, basal ganglia, gray cerebellum gray and meniscus white. See you in the next video.