Neuroanatomy (Part 2)
The Central Nervous System
The Brain
The brain is divided in three major parts: the forebrain, midbrain, and hindbrain.
The forebrain is further subdivided into two: the telencephalon and the diencephalon. On the other hand the midbrain is composed of the structures within the mesencephalon. And in turn the hindbrain consists of the metencephalon and the myelencephalon.
The Forebrain
The telencephalon of the forebrain is made up of the cerebrum and the basal ganglia, while the diencephalon is composed of the thalamus, hypothalamus, subthalamus, and epithalamus.
The Cerebrum
The cerebrum consists of two hemispheres (Figure 12), which together form the largest part of the brain. The structures in the left hemisphere have very similar counterparts in the right hemisphere. One hemisphere is connected to the other by means of the massive bundle of nerve fibers known as the corpus callosum. Each hemisphere is composed of an outer and an inner layer (Figure 13). The outer layer is known as the cerebral cortex. The cerebral cortex is composed of the soma or neuronal cell bodies. These structures make the cortex gray (gray matter). On the other hand, the inner layer is composed of the nerve fibers of those somas located in the cortex. Since these fibers are white, they are collectively known as the white matter.
Figure 12. Cerebral Hemispheres
Figure 13. Gray and white matter
The cerebral cortex is heavily folded. The folds are called gyri, and the grooves between them are known as sulci (or fissures if they are unusually deep).
One hemisphere has functions which make it distinct from the other. The left hemisphere controls the right part of the body, while the right hemisphere controls the left part of the body. Usually the dominant of the two hemispheres is the left. Thus more people manifest with right handedness rather than left handedness.
The contralateral functioning of each hemisphere is due to the bifurcations of the nerve fibers either at the cervicomedullary junctions or at the spinal cord. These bifurcations will be further discussed at the latter section of this discourse.
The table below discusses the functions of the dominant and the non-dominant hemispheres of the cerebrum.
To be continued...
The Brain
The brain is divided in three major parts: the forebrain, midbrain, and hindbrain.
The forebrain is further subdivided into two: the telencephalon and the diencephalon. On the other hand the midbrain is composed of the structures within the mesencephalon. And in turn the hindbrain consists of the metencephalon and the myelencephalon.
The Forebrain
The telencephalon of the forebrain is made up of the cerebrum and the basal ganglia, while the diencephalon is composed of the thalamus, hypothalamus, subthalamus, and epithalamus.
The Cerebrum
The cerebrum consists of two hemispheres (Figure 12), which together form the largest part of the brain. The structures in the left hemisphere have very similar counterparts in the right hemisphere. One hemisphere is connected to the other by means of the massive bundle of nerve fibers known as the corpus callosum. Each hemisphere is composed of an outer and an inner layer (Figure 13). The outer layer is known as the cerebral cortex. The cerebral cortex is composed of the soma or neuronal cell bodies. These structures make the cortex gray (gray matter). On the other hand, the inner layer is composed of the nerve fibers of those somas located in the cortex. Since these fibers are white, they are collectively known as the white matter.
Figure 12. Cerebral Hemispheres
Figure 13. Gray and white matter
The cerebral cortex is heavily folded. The folds are called gyri, and the grooves between them are known as sulci (or fissures if they are unusually deep).
One hemisphere has functions which make it distinct from the other. The left hemisphere controls the right part of the body, while the right hemisphere controls the left part of the body. Usually the dominant of the two hemispheres is the left. Thus more people manifest with right handedness rather than left handedness.
The contralateral functioning of each hemisphere is due to the bifurcations of the nerve fibers either at the cervicomedullary junctions or at the spinal cord. These bifurcations will be further discussed at the latter section of this discourse.
The table below discusses the functions of the dominant and the non-dominant hemispheres of the cerebrum.
To be continued...
