Macroscopic Structure and Basic Divisions
The central nervous system within the cranial cavity has a complex organization. The entire organ is subdivided into three main parts: the brainstem, the cerebellum, and the cerebrum. Each of these divisions features unique phylogenetic development during evolution, specific ontogenetic maturation features, and distinct anatomical and functional specializations.
The largest and most massive component is the cerebrum, which derives from the telencephalon. It occupies the predominant part of the intracranial space. The deep longitudinal fissure of the cerebrum (fissura longitudinalis cerebri) runs medially, completely dividing this mass into two halves: the right cerebral hemisphere (hemispherium cerebri dextrum) and the left cerebral hemisphere (hemispherium cerebri sinistrum). Posteriorly lies the transverse cerebral fissure (fissura transversa cerebri), which serves as the anatomical boundary separating the hemispheres from cerebellar structures.
Morphofunctional Systems of the Hemispheres
Within the cerebral hemispheres, three major systems have phylogenetically and functionally evolved:
- Olfactory brain (rhinencephalon).
- Basal nuclei (nuclei basales) — aggregations of gray matter.
- Cerebral cortex (cortex cerebri, also called the pallium).
The gray matter of all these systems forms a complex network of interactions. These functional connections are mediated by projection and association pathways running through the white matter of the hemispheres, integrating the activity of different regions into a unified process.
Hierarchy of Functional Organization
From an anatomofunctional perspective, the work of the entire system can be divided into four hierarchical levels of regulation:
- Level I — the sphere of highest control. It governs all sensation and motor activity. Processes of logical thinking, complex memory, and imagination are localized here. The anatomical substrate of this level is the cerebral cortex (cortex cerebri).
- Level II — regulates unconscious (involuntary) movements and maintains optimal muscle tone. The base for these processes is formed by the basal nuclei (nuclei basales).
- Level III — acts as the center for emotional control and actively participates in endocrine regulation. Its basis is the limbic system, which includes structures such as the hippocampus, pituitary gland, hypothalamus, cingulate gyrus, and amygdala.
- Level IV — responsible for basic vegetative life-support functions and signal transmission between various neural centers. This level is represented by the reticular formation and other integrating centers of the brainstem.
Anthropometric Parameters: Weight and Dimensions
Organ parameters can vary, but the following average anatomical values are characteristic of an adult:
- Total normal weight averages 1375 grams, with a broad individual norm ranging from 900 to 2000 grams.
- Average neural tissue volume is approximately 1200 cm³.
- Sagittal (anteroposterior) dimension ranges from 16 to 17 centimeters.
- Transverse dimension is 13–14 centimeters.
- Vertical dimension (height) ranges between 10.5 and 12.5 centimeters.
An interesting feature is that male brain weight is on average slightly greater than that of females. Importantly, there is no direct correlation between brain mass and a person's level of intellectual giftedness or talent.