Diencephalon: Structure, Functions And Curiosities

The central nervous system (CNS) is divided into two parts: the brain and the spinal cord. The brain is the innermost part of the skull and contains one of the main structures of the brain, the diencephalon.

This structure is involved in the control of emotional behavior, the regulation of consciousness, the autonomic nervous system, sleep and other factors. Let’s go further .

What is the diencephalon?

The diencephalon derives from the forebrain or forebrain, the most frontal part of the brain during early embryonic development. As it grows, the prosencephalon divides into a diencephalon and a telencephalon until it becomes a bridge between the midbrain and the telencephalon.

It is located under the corpus callosum and the fornix, and is connected at the sides to the hemispheres of the telencephalon. Thus, it is located in the central part of the brain.

The structures of the diencephalon have connections with the rest of the nervous system, including the cortical and subcortical areas. It is therefore a center which sends and receives nerve signals (respectively afferents and efferences) and represents a fundamental role for the proper functioning of multiple biological processes.

Structure and functions of the diencephalon

The diencephalon consists of 4 main structures. They are as follows:

Epithalamus

• Structure: the epithalamus contains the pineal gland or epiphysis, the nuclei of the habenula, the thalamic medullary striae, the posterior white commissure, the commissure of the habenula, the lamina tectoria and the choroid plexuses

• Functions: it regulates the circadian rhythms of hormonal secretions, mainly linked to chiaroscuro cycles. It also influences the gonadal sphere (testes and ovaries) and is also responsible for the secretion of melatonin

Thalamus

• Structure: It is divided into anterior thalamus, medial thalamus and lateral thalamus. The latter in turn contains a dorsal, ventral and metallic region
• Functions: it functions as a relay between cortical and subcortical connections. It is a receptor of sensory afferents, with the exception of the olfactory afferents which arrive directly to the cortex. It is also involved in the regulation of consciousness and the sleep cycle

Subthalamus

• Structure: it is composed of the subthalamic nucleus of Luys, the uncertain zone, the preruptive field of Forel, the globus pallidus and the compact dorsal and ventral reticular portions of the substantia nigra

• Functions: it participates in the regulation of movements and is linked to the production of dopamine and therefore to the brain’s reward system

Hypothalamus

• Structure: it divides, from front to back, into the anterior, middle and posterior hypothalamus. It contains a periventricular, median and lateral zone
• Functions: it is the center of regulation of visceral functions through the vegetative and endocrine systems. In addition, it regulates emotional behavior through the limbic system, maintains homeostasis and builds the hormones vasopressin and oxytocin.

In addition to these structures, the diencephalon has a cavity, called the third ventricle, which is located below the thalamus. This ventricle allows the circulation of cerebrospinal fluid and helps maintain the shape and structure of the brain while keeping it healthy.

Interesting data on the diencephalon

The diencephalon is this control center that causes our body to maintain its internal balance or homeostasis. Here are some of its curiosities:

• It represents only 2% of the total weight of the nervous system
• The pituitary gland, attached to the hypothalamus, which participates in processes such as reproduction and growth through the action of hormones
• It maintains body temperature
• It regulates appetite and therefore food
• Habenula, which is part of the epithalamus, is linked to fear and depression
• It regulates the endocrine activity of the adenohypophysis
• It is the main modulator of the functioning of the vegetative nervous system

The diencephalon, stress and emotions

The diencephalon is also involved in neuroendocrine responses to stress. In fact, the journal Dialogues in Neuroscience published a study on the relationship between the hypothalamic-pituitary-adrenal axis and stress. It is postulated that animals, in order to respond to stress, activate a series of physiological and behavioral responses associated with this axis.

The authors explain stress as a state of real or perceived threat; since the hypothalamus regulates homeostasis, it enters into the management of the situation by working in concert with the nervous, endocrine and immune systems.

The hypothalamus has also been shown to be extremely important in generating emotional behavior. For example, H. Nakao, in a study published in the American Journal of Physiology , found that stimulation of the hypothalamus in cats by implanted electrodes resulted in aggressive responses.

Thanks to the diencephalon, a little-known “great manager”, communication between the cortical and subcortical levels is made possible. It also allows us to maintain the balance of our body and the regulation of our emotions, always in parallel with other systems. A control center as wonderful as it is efficient.

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