Welcome to this module. In this module, we'll be discussing the developmental and vascular organization of the brain. When we compare our brains across species, we see a great variability in size and shape, between simple animals like a frog all the way up to humans. But when you look at these cross sections of their brains, you also notice a great overlap in basic brain organization. For example, when we look at these MRI images of a human on the left and a monkey on the right, we see great similarities in the basic structures. For example, the cortex pointed out here is, although different in size, very similar between the two. The brainstem including the spinal cord is also very similar. The thalamus which is essentially a relay station important for communication within the brain is very similar, as well as the cerebellum, a structure that is critically important for fine motor control. When we look at these cross-sections of a human on the left and a chimpanzee on the right, we also see great similarities. The corpus callosum which is a bundle of neurons that facilitates communication between the two brain halves, is very similar between these two. As are the hippocampi. The hippocampus is a structure critically important for memory formation and is also very similar in its organization and structure between the animal and the human. Finally, in fact the entire thalamus and midbrain, important for basic life functions, breathing, heart rate but also locomotion and motor control are very similar between this chimpanzee brain and the human brain. But it's even beyond the monkey brains that we can make comparisons. On the left here you see a schematic representation of the brain of a mouse which also has very similar basal structures compared to the human brain. Including the ventricles, the striatum, the thalamus again all structures that are very important for communication in the brain but also locomotion and basic life functions. If you look at the image on the right, you will see that the largest difference between these brains is the size of the cortex. In fact the subcortical brain structures, the basic brain structures of the brainstem etcetera, are very similar between the mouse brain, the cat brain in the middle, and the human brain on the far right. This confirms the great similarities in brain organizations, but again the differences in cortex size across these species. The advantage of these similarities is that it allows experiments in simpler life forms such as the rat or the mouse model that can then be used to inform findings in human neuroscience. The importance of this, the cortex, and also the similarities between the species is also represented in the developmental progress of the brain. On the left you'll see the development of a three week old fetus all the way up to a newborn, and on the right-hand side you can see the development of the neural tube into the spinal cord initially, then the hindbrain which again includes the cerebellum and some of the mid-brain structures. The tectum and the tegmentum which form the midbrain, and finally the endbrain which includes the cortex which is the largest difference between these species. The cortex forms last and represents the largest difference between humans and simpler life forms. So in addition to the developmental anatomy of the brain, we will now discuss a little bit of the vascular anatomy of the human brain. The brain consumes a tremendous amount of energy and oxygen, which is supplied by a highly intricate systems of arteries and veins as you see in these images here. As you see in the right-hand image, the top of the image represents the top of the brain and as you go down further into the brain, deeper into the brain, you'll see the density of the arteries and veins that supply the blood to those regions. Blood is supplied through the internal carotid artery, which originates initially from the aorta. At first this is through the common carotid artery, which then splits off to the external carotid artery which supplies blood to the face and the rest of the head. And then the internal carotid artery which supplies, which forms the primary blood supply to the brain. So blood is supplied through the internal carotid artery which then terminates into the circle of Willis which distributes the blood throughout the brain. In the middle here, you see an actual photograph of the circle of Willis which is at the bottom of the brain. And on the right-hand side you see a schematic representation of the arteries and veins that come off the circle of Willis. So the middle cerebral artery is the primary blood supply to the circle of Willis, which then distributes the blood through a series of arteries and veins including the anterior cerebral artery, the middle cerebral artery, the posterior cerebral artery, the superior cerebellar artery, the Pontin's arteries, the anterior inferior cerebellar artery, the vertebral artery and finally the posterior inferior cerebellar artery. Each of these arteries supplies a very specific and distinct area of the brain with blood. This allows us to create cortical vascular territories or areas of the brain that are supplied by a particular artery or vein system. This becomes important later when we're talking about FMRI research and the origination of the MR signal. So we've discussed a little bit of the developmental and vascular anatomy of the brain to provide an understanding of the basic anatomy. In the next module, we'll discuss some basic terminology that is commonly used to explain locations and relative positions in the brain.
