Anatomy of the Spinal Cord and Brain | Cerebrum, Cerebellum, and Brainstem
Anatomy of the Spinal Cord and Brain | Cerebrum, Cerebellum, and Brainstem
Objective 7
List and label the most important structures of the brain.
This is the human brain in lateral view. In order to understand its anatomy, we have to understand how such a complex and elaborate structure develops.
The central nervous system of the human begins to develop shortly after gastrulation, the formation of three primordial layers that occurs 16 days post-conception (30 days since the last period). A part of the future skin (ectoderm) begins to thicken, forming a neural plate. The plate then develops a shallow groove that deepens into a neural fold over the next few days.
The edges of this groove fold up and seal together forming a neural tube. This tube then begins to change shape and develop empty rooms called vesicles. The first set of three vesicles are called primary brain vesicles. The second set of vesicles are called secondary brain vesicles and we need to learn the names of these because those will help us understand the anatomy of the adult nervous system.
These subdivisions of the developing brain become adult structures, as shown in the table. Because each of these areas has a different anatomy and different strategy of “brain wiring”, it’s important to understand just a little bit about the development of the brain to understand the anatomy and function of the brain.
For example, the cerebral cortex and basal nuclei, which represent the vast majority of the weight of the human brain, are extensively interconnected and control much of human behavior. The basal nuclei smooth out the activity of the part of cerebral cortex that controls muscles; this smoothing goes wrong in Parkinson disease. Changes in the activity of another part of the basal nuclei is implicated in obsessive-compulsive disorder. We will examine some of the signaling molecules and wiring of this system in Unit 12, and we will describe what goes wrong with signaling in the basal nuclei in the Pathophysiology course.
(Many authorities call the basal nuclei the basal ganglia. I believe this is confusing; a ganglion, as we’ve just discussed, is a collection of nerve cell bodies in the PNS. The basal nuclei fit squarely within the CNS. That’s a good reason to go through the hassle of changing the name for our sons and daughters who might have to learn neuroanatomy later.)
This table contains the names of all the brain structures we need to learn at this point in the course.
A deep groove, the medial longitudinal fissure, divides the brain into a left hemisphere and right hemisphere. These are connected by the corpus callosum, a band of axons running between mirror-image areas of the brain, right and left.
First, we’ll divide the external surface of the cerebral cortex into four lobes.
The frontal lobe (wait for it…) is in front. (left)
The parietal lobe shares its borders with the other three external lobes. It is just posterior to the frontal lobe. (right)
The temporal lobe (wait f