Constructing a three-dimensional visualization of the brain and its various parts is a challenging task for most people, and this diagram and its companion (the next illustration) are designed to assist the learner in this task.
This is a semi-anatomic representation of the brain and the parts of the CNS. This general diagrammatic view should be consulted as the learner is orienting to the placement of the structures within the brain. These same structures are viewed from the lateral perspective with the next illustration.
The cerebral hemispheres: The large cerebral hemispheres, with its extensive cerebral cortex, is by far the most impressive structure of the CNS and the one that most are referring to when speaking about "the brain." In fact there are two cerebral hemispheres that are connected across the midline by a massive communication link called the corpus callosum (see Figure 16 and Figure 19A). The hemispheres are discussed with Figure 13-Figure 19 of the Orientation section.
Many parts of the brain are found deep inside the hemispheres. This illustration is done so that these structures should be visualized "within" the hemispheres. Included are:
• Basal ganglia: These large neuronal areas are found within the brain; its three parts are shown — the caudate nucleus (head and tail), the putamen, and the globus pallidus. The basal ganglia are discussed with Figure 22-Figure 30 of the Orientation section.
• Ventricles of the brain: Each hemisphere has within it a space remaining from the neural tube, from which the brain developed, called a ventricle — the lateral ventricle (also called ventricles 1 and 2). The ventricles are presented in this anterior perspective with Figure 20B.
The massive cerebral hemispheres hide the other parts of the brain from view, when looking from the anterior perspective, although some of these parts can be seen if the brain is viewed from below (see Figure 15A and Figure 15B). These structures include:
• Diencephalon: The largest part of the dien-cephalon is the thalamus; in fact, this is a paired structure. The unpaired third ventricle should be noted between the thalamus of each side. The thalamus is discussed with Figure 11 and Figure 12 of the Orientation section.
• Brainstem: By definition, the brainstem consists of the midbrain, pons, and medulla; the cranial nerves are attached to the brainstem. The brainstem and cranial nerves are considered in Figure 6-Figure 10 of the Orientation section. The ventricular space within the brain-stem is the fourth ventricle.
• Cerebellum: Part of the cerebellum can be seen from this perspective. This "little brain" is usually considered with the brainstem and is discussed with Figure 9A and Figure 9B of the Orientation section.
• Spinal cord: This long extension of the CNS continues from the medulla and is found in the vertebral canal. The spinal cord is discussed with Figure 1-Figure 5 of the Orientation section.
Note on the safe handling of brain tissue: Current guidelines recommend the use of disposable gloves when handling any brain tissue, to avoid possible contamination with infectious agents, particularly the "slow" viruses. In addition, formalin is a harsh fixative and can cause irritation of the skin. Many individuals can react to the smell of the formalin and may develop an asthmatic reaction. People who handle formalin-fixed tissue must take extra precautions to avoid these problems. In most labs, the brains are soaked in water before being put out for study.
F = Frontal lobe T = Temporal lobe
Ch = Caudate head Ct = Caudate tail P = Putamen GP = Globus pallidus
LV = Lateral ventricle
3 = 3rd ventricle Aq = Aqueduct
4 = 4th ventricle
D = Diencephalon (thalamus) C = Cerebellum
Sc = Spinal cord Cc = Central canal
FIGURE OA: Overview Diagram — Anterior View
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