The thalamus, also called the thalamus, is located next to the third ventricle of the brain. The ventricles, in turn, are cavities in which 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 interaction between the cerebral cortex and underlying structures.
Main 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, there are about 120 nuclei in the thalamus. Depending on the location of the core, they are classified into the following groups:
- Front.
- Lateral. The back of this group, in turn, is subdivided intopillow, medial and lateral geniculate bodies.
- Medial.
Depending on the functions, the kernels are classified into the following groups:
- specific;
- associative;
- non-specific.
Specific cores
This group of thalamus nuclei has a number of distinctive features that unite them. First, they receive impulses from long neural pathways that transmit information from somatosensory, visual, and auditory receptors to the cerebral cortex. Through these nuclei, the impulse is transmitted further to the corresponding areas of the cortex: somatosensory, auditory and visual. In addition, information from them enters the premotor and motor areas of the cortex.
Also, specific nuclei receive feedback from the cortex. Experiments have shown that when a portion of the cortex corresponding to a specific nucleus is removed, this nucleus is also destroyed. And when certain nuclei are stimulated, the nerve cells of the cortex corresponding to them are activated.
This group receives information from the cortex, reticular formation, brain stem. It is because of the presence of these connections that the cerebral cortex has the ability to select the most important information at the moment from all incoming information.
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 areas of the cortex.
Associative cores
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 implement 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 due to the presence of this area of the cortex and associative nuclei that such processes as recognition of objects, coordination of speech with motor activity, understanding of the three-dimensionality of space and awareness of oneself in this space are possible.
Non-specific 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. Through the ascending pathways, 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
Thalamus is a key formation in the transmission of nerve impulses to the cerebral cortex. When the cortex is damaged, it is thanks to the work of the thalamus that it is possible to partially restore such functions as touch, sensation of pain and temperature.
Another important function of the thalamus is the integration of motor and sensory activities. This is possible due to the flow of information into the thalamus from both the motor and sensory centers of the nervous system.
In addition, the thalamus is necessary for attention and consciousness. He alsotakes part in the formation of behavioral responses.
Due to the connection with the hypothalamus, which will be discussed later in the article, the functions of the thalamus also cover memory, emotional behavior.
Hypothalamus
This structure is the main regulator of the autonomic and endocrine functions of the body. It is located under the visual tubercle and the third ventricle. The nuclei are also the main structural part of the hypothalamus, but there are much fewer of them.
Depending on localization, the following groups of nuclei are distinguished:
- anterior - paraventricular, suprachiasmatic;
- middle - infundibular nucleus;
- posterior - the nuclei of the mamillary bodies.
Hypothalamus functions
The following is a list of the main functions of this structure:
- controlling the activity of the autonomic nervous system;
- organization of behavior (food, sexual, parental, emotional behavior, etc.);
- body thermoregulation;
- secretion of hormones: oxytocin, which increases the contractile activity of the uterus; vasopressin, which increases the absorption of water and sodium in the renal tubules.
The functions of the hypothalamus listed above 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 and electrolyte composition, the amount of hormones in it, glucose concentration, etc.).
So the diencephalon(thalamus and hypothalamus in general) has many important functions, thanks to which normal life activity is possible.
