The thalamus, also called the visual tubercle, is located next to the third ventricle of the brain. The ventricles, in turn, are cavities in which the cerebrospinal fluid (CSF) circulates. It is part of the diencephalon (diencephalon). In the vast majority of people, the thalamus is divided into two parts, interconnected by gray matter. Around this formation is bordered by an internal capsule that separates it from the basal ganglia. This capsule consists of nerve fibers that provide the interaction of the cerebral cortex with the underlying structures.
Core cores
The structure of this formation is quite complex, which is explained by a wide range of functions performed by the thalamus. The main component of the thalamus is the nucleus, formed from the gray matter of the brain, that is, the bodies of nerve cells. In total, the thalamus has about 120 cores. Depending on the location, the kernels are classified into the following groups:
- Front
- Lateral. The back of this group, in turn, is divided into a pillow, medial and lateral cranked bodies.
- Medial.
Depending on the functions, the kernels are classified into the following groups:
- specific;
- associative;
- non-specific.
Specific cores
This group of nuclei of the optic tubercle has a number of distinctive features that unite them. Firstly, they receive impulses from the long neural pathways, which ensure the transfer of information from somatosensory, visual and auditory receptors to the cerebral cortex. Through these nuclei, the impulse is transmitted further to the corresponding sections of the cortex: somatosensory, auditory and visual. In addition, information from them enters the premotor and motor sections of the cortex.
Specific nuclei also receive feedback from the cortex. In experiments, it was proved that when a portion of the cortex corresponding to a specific core is removed, this core also collapses. And when certain nuclei are stimulated, nerve cells of the corresponding cortex are activated.
This group receives information from the cortex, reticular formation, brain stem. It is because of the presence of these connections in the cerebral cortex that it is possible among all the incoming information to select the most important at the moment.
In addition, the structure of the thalamus includes nuclei that receive information from the red and basal nuclei, the limbic system, the dentate nucleus (located in the cerebellum). Next, the signal goes to the motor zones of the cortex.
Associative kernels
A feature of this group of nuclei is that they receive already processed signals from other parts of the thalamus.
Thanks to their work, it is possible to carry out integrative processes in which generalized signals are formed. Then they are transmitted to the associative areas of the cerebral cortex (frontal, parietal and temporal lobes). It is thanks to the presence of this section of the cortex and associative nuclei that processes such as recognition of objects, coordination of speech with motor activity, understanding of the three-dimensionality of space and self-awareness in this space are possible.
Nonspecific Nuclei
These nuclei consist of small nerve cells that receive information from neurons of other thalamic nuclei, the limbic system, the basal ganglia, the hypothalamus, and the brain stem. On the ascending paths, the nuclei receive signals from pain and temperature receptors, and through the reticular formation - from almost all other structures of the central nervous system.
Main functions
The thalamus is a key formation in the transmission of nerve impulses to the cerebral cortex. If the cortex is damaged, it is precisely thanks to the work of the thalamus that partial restoration of such functions as touch, sensation of pain and temperature is possible.
Another important function of the thalamus is the integration of motor and sensory activity. This is possible due to the entry into the thalamus of information from both the motor and sensory centers of the nervous system.
In addition, the thalamus is necessary to provide attention and consciousness. He also takes part in the formation of behavioral reactions.
Due to the connection with the hypothalamus, which will be discussed later in the article, the functions of the thalamus also include memorization, emotional behavior.
Hypothalamus
This structure is the main regulator of the autonomic and endocrine functions of the body. It is located under the optic tubercle and III ventricle. The nucleus is also the main structural part of the hypothalamus, but there are much fewer nuclei.
Depending on localization, the following groups of nuclei are distinguished:
- front - paraventricular, suprachiasmen;
- middle - infundibular nucleus;
- back - nuclei of the mamillary bodies.
Hypothalamus functions
Below is a list of the main functions of this structure:
- management of the activity of the autonomic nervous system;
- organization of behavior (food, sexual, parental, emotional behavior, etc.);
- body thermoregulation;
- hormone secretion: oxytocin, which increases the contractile activity of the uterus; vasopressin, which increases the absorption of water and sodium in the renal tubules.
The above functions of the hypothalamus are provided due to the presence of various centers in it, as well as specific nerve cells. They are able to respond to changes in the state of the body (blood temperature, water-electrolyte composition, the amount of hormones in it, glucose concentration, etc.).
Thus, the diencephalon (thalamus and hypothalamus mainly) has many important functions, due to which normal functioning is possible.