An Introduction to the Brain | Virtual Anatomy Dissection
by Robert Tallitsch, PhD | November 9, 2021
An Introduction of the brain and a simplified explanation of dementia, including a patient case example, symptoms, causes, and treatments - use this article and video in your class!
Written by: Robert Tallitsch, PhD
The brain is a very complex structure, containing approximately 20 billion neurons (nerve cells), which allows it to perform an amazing number of functions. What follows is a brief introduction to the three-dimensional anatomy of the brain, its subdivisions, and the ventricles of the brain.
The brain consists of three subdivisions:
- The cerebrum
- The brain stem, which is further subdivided into the:
• Diencephalon
• Mesencephalon
• Pons (metencephalon)
• Medulla oblongata (myelencephalon)
- Cerebellum
Cerebrum
The cerebrum is the largest part of the brain. It is subdivided into two cerebral hemispheres by the longitudinal fissure. Each cerebral hemisphere communicates with the contralateral hemisphere by the corpus callosum. Each hemisphere is composed of a highly convoluted cortex and underlying white matter. The superficial gray matter of the cortex contains neurons and neuroglia, the cellular elements of the central nervous system. Neurons process and transfer information throughout the nervous system. Neuroglia provide a supporting framework for the nervous system, isolate the neurons, and help maintain the intercellular environment. The deeper white matter, which moves information from one place to another within the CNS (brain and spinal cord), is composed of neuronal processes.
The surface of the cerebrum is convoluted by folds, termed sulci, and ridges, termed gyri. The cerebrum is subdivided into lobes by the larger, named sulci. The lobes of the brain are named according to the bone of the skull that is immediately superficial to them.
Lobes of the Cerebrum
The frontal lobe, which is the largest lobe of the cerebrum, lies deep to the frontal bone of the skull. The posterior boundary of the frontal lobe is the central sulcus, and the inferolateral boundary is the lateral sulcus.
The parietal lobe is deep to the parietal bone of the skull, and has three principal areas associated with it. The postcentral gyrus runs parallel and caudal to the central gyrus. The superior and inferior parietal lobules are other major areas of the parietal lobe.
Deep to the temporal bone is the temporal lobe. This lobe has three prominent gyri: the superior, middle, and inferior temporal gyri.
The occipital lobe lies deep to the occipital bone of the skull.
The limbic lobe is a “synthetic lobe” of the brain, in that it contains gyri, deeper nuclei (clusters of neurons) and tracts found between the borders of the diencephalon and cerebrum. This lobe is associated with emotions and behaviors that are ultimately related to the preservation of the individual.
Motor and Sensory Areas of the Cerebral Cortex
The processing of motor and sensory information and numerous intellectual functions are associated with the cerebral cortex.
The central sulcus of the cerebrum separates the motor and sensory areas of the cerebrum. The primary motor area of the cerebrum, which initiates voluntary motor movements, is associated with the precentral gyrus. The primary somatosensory area, which receives sensory information associated with pressure, touch, pain, temperature, and taste, is associated with the postcentral gyrus.
The occipital lobe is associated with visual stimuli, while auditory and olfactory stimuli are associated with the temporal lobe. In addition, all lobes of the cerebrum are involved in the integration and processing of sensory data and the initiation and processing of motor activities.
Association Areas of the Cerebral Cortex
Each sensory and motor area of the cerebrum is closely associated with an association area, also within the cerebrum. These association areas of the cerebral cortex are responsible for the interpretation (integrating and understanding) of motor and sensory information.
Brain Stem
Diencephalon
The diencephalon, which is composed of the epithalamus, right and left thalami, and hypothalamus, connects the brainstem to the cerebrum. Almost all of the sensory and motor information of the CNS synapses within the diencephalon.
Mesencephalon
The mesencephalon, or midbrain, contains motor nuclei of the reticular formation, and sensory nuclei that process auditory and visual stimuli.
Pons
The pons, which contains ascending, descending, and transverse sensory and motor tracts, also contains motor and sensory nuclei for cranial nerves V, VI, VII and VIII.
Medulla
The spinal cord connects to the brain at the medulla oblongata. The medulla contains nuclei (groups of neurons) that function as cardiovascular reflex centers, respiratory rhythmicity centers, motor and sensory relay and processing centers, and nuclei for cranial nerves VIII, IX, X, XI and XII.
Cerebellum
The cerebellum is subdivided into two cerebellar hemispheres that are connected by the vermis. Unlike the cerebrum, the two hemispheres of the cerebellum do not communicate with each other.
Like the cerebrum, the cerebellum has a superficial cortex and deeper white matter. The surface of the cerebellum is convoluted, possessing folds termed folia cerebelli.
The cerebellum is functionally connected to almost every part of the brain, but its main connections are with the cerebrum, spinal cord, and internal ear. Functionally, each half of the cerebellum coordinates muscular activities on its ipsilateral side.
Ventricles of the Brain
There are four ventricles within the brain: Two lateral ventricles (one within each cerebral hemisphere), the third ventricle within the diencephalon, and the fourth ventricle located between the pons and cerebellum and extending into the medulla oblongata.
Each ventricle possesses a choroid plexus. These choroid plexi produce cerebrospinal fluid (CSF), and remove wastes from the CSF. CSF that is formed within the lateral ventricles flows into the third ventricle. CSF then passes from the third ventricle through the cerebral aqueduct and into the fourth ventricle. Most of the CSF of the fourth ventricle flows into the subarachnoid space of the brain and spinal cord. The small amount of CSF that remains passes inferiorly into the central canal of the spinal cord.
Summary
The brain is a complex organ that is capable of learning and retaining a wealth of information. Through a not-yet-understood process, this mass of cells and neuronal processes, all of which has the consistency of unset jello, makes each of us into the individual that we are.
Dive deeper into the brain with real 3D anatomy using BodyViz virtual dissection platform! See the anatomy of real patients, like the visualizations used in the Brain Builder video at the beginning of this blog, to give your students unlimited learning opportunities with real anatomy! With BodyViz, instructors and students can virtually dissect real human anatomy from their computer, instead of using plastic modeled anatomy. Schedule a demo to learn more about how you can implement BodyViz into your classroom!
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