Macroscopic structure and basic parts
The central nervous system within the cranial cavity has a complex structure. The entire organ is subdivided into three main parts: the brainstem, the cerebellum, and the cerebrum. Each of these parts has its own unique features of phylogenetic development in the course of evolution, specific features of ontogenetic maturation, and its own anatomical and functional specifics.
The largest and most massive component is the cerebrum (cerebrum), which originates from the telencephalon. It fills the predominant part of the intracranial space. A deep longitudinal fissure of the cerebrum (fissura longitudinalis cerebri) runs along the midline. It completely divides this mass into two halves — the right hemisphere (hemispherium cerebri dextrum) and the left hemisphere (hemispherium cerebri sinistrum). In the posterior part of the organ lies the transverse cerebral fissure (fissura transversa cerebri), which serves as the anatomical boundary separating the hemispheres from the structures of the cerebellum.
Morphofunctional systems of the hemispheres
Historically (phylogenetically) and functionally, three major systems have formed within the cerebral hemispheres themselves:
- Olfactory brain (rhinencephalon).
- Basal nuclei (nuclei basales) — clusters of gray matter.
- Cerebral cortex (cortex cerebri, also called pallium or mantle).
The gray matter of all these systems forms a most complex network of interactions. These functional connections are carried out through projection and association pathways passing through the white matter of the hemispheres, which makes it possible to integrate the work of different areas into a single process.
Hierarchy of functional organization
From anatomical and functional perspectives, the work of the entire system can be divided into four hierarchical levels of regulation:
- Level I — the sphere of highest control. It manages all sensitivity and motor activity of the body. The 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 basis for these processes is formed by the basal nuclei (nuclei basales).
- Level III — acts as the emotional control center and actively participates in the regulation of the endocrine system. Its basis is the limbic system. Its composition includes structures such as the hippocampus, pituitary gland, hypothalamus, cingulate gyrus, and amygdala.
- Level IV — is responsible for basic vegetative life-support functions and ensures signal transmission between various nerve centers. This level is represented by the reticular formation and other integrating centers of the brainstem.
Anthropometric indicators: weight and dimensions
The parameters of the organ can vary, but the following average anatomical values are typical for an adult:
- The total mass normally averages 1375 grams. At the same time, the boundaries of the individual norm are quite wide — from 900 to 2000 grams.
- The average volume of nervous tissue is approximately 1200 cm³.
- The sagittal (anteroposterior) dimension ranges from 16 to 17 centimeters.
- The transverse dimension is 13–14 centimeters.
- The vertical dimension (height) is within the range of 10.5–12.5 centimeters.
An interesting feature is the fact that in men, the brain mass is on average slightly larger than in women. At the same time, it is important to note: there is no direct relationship between the mass of the brain and the degree of intellectual giftedness or talent of a person.
Briefly: answers to topical questions
Which specific nuclei form the system of basal nuclei (nuclei basales)?
The system of basal nuclei is formed by clusters of gray matter within the white matter of the hemispheres. These include:
- Corpus striatum (corpus striatum) — includes the caudate nucleus (nucleus caudatus) and lentiform nucleus (nucleus lentiformis).
- Claustrum (claustrum) — separated from the putamen by the external capsule.
- Amygdaloid body (corpus amygdaloideum).
The lentiform nucleus is additionally divided by layers of white matter into the putamen (putamen) and globus pallidus (globus pallidus).
Which lobes are distinguished in the cerebral cortex?
Five lobes are distinguished in the cerebral cortex. These include:
- Frontal lobe (lobus frontalis).
- Parietal lobe (lobus parietalis).
- Occipital lobe (lobus occipitalis).
- Temporal lobe (lobus temporalis).
- Insular lobe (lobus insularis or insula) — located deep within the lateral sulcus of the cerebrum and separates the frontal lobe from the temporal lobe.
Which vital autonomic centers are localized in the brainstem?
Vital centers regulating respiration and blood circulation are localized in the brainstem. Within the structures of the reticular formation, the following are distinguished:
- Respiratory center — located in the medulla oblongata (inspiratory and expiratory divisions), and also includes the pneumotaxic center at the level of the pons.
- Vasomotor center — located in the medulla oblongata, responsible for the regulation of blood pressure and cardiac activity.
Which parts of the brain develop from the rhombencephalic vesicle (rhombencephalon)?
The structures of its caudal, middle, and lateral parts develop from the hindbrain (rhombencephalon). These include:
- Medulla oblongata (medulla oblongata) — is the caudal part of the hindbrain and a derivative of the myelencephalon.
- Cerebellum (cerebellum) — develops from the cerebellar plate, which belongs to the middle and lateral parts of the hindbrain.
To memorize the 4 levels of functional organization, move "from top to bottom": Cortex (I — logic and imagination) → Basal nuclei (II — muscle tone) → Limbic system (III — emotions and hormones) → Brainstem (IV — autonomics and connections).
Class and exam questions
Does brain mass affect the level of intelligence?
No, the size and mass of the organ (ranging from 900 to 2000 g) do not correlate with intellectual abilities. A direct link between brain mass and giftedness has not been scientifically proven.
Which structure separates the right and left hemispheres?
The right and left cerebral hemispheres are completely separated by the deep longitudinal cerebral fissure (fissura longitudinalis cerebri).
What is the anatomical basis for emotional control?
The center of emotional control (III functional level) is the limbic system. It includes the hippocampus, hypothalamus, amygdala, cingulate gyrus, and pituitary gland.
What else to study on this topic
- Anatomy and functions of the olfactory brain (rhinencephalon)
- Basal nuclei (nuclei basales): topography and connections
- Structure of the cerebral cortex (cortex cerebri)
- Brainstem and reticular formation
- Limbic system: hippocampus, hypothalamus, and amygdala
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