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 most anterior part inside the skull and contains one of the main structures of the brain: the diencephalon.

This structure is involved in the control of affective behavior, regulation of consciousness, the autonomic nervous system, sleep and other factors. Let’s dig deeper.

Diencephalon, what is it?

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

It is located below the corpus callosum and the fornix, and joins on the sides with the hemispheres of the telencephalon. Thus, it is located in the middle part of the brain.

The structures of the diencephalon have connections with the rest of the nervous system, including with cortical and subcortical areas. Therefore, it is a center that sends and receives nervous signals (afferents and efferents, respectively) 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 the following:

Epithalamus

Structure. The epithalamus contains the pineal gland or epiphysis, the nuclei of the habenula, the thalamic stria medullaris, the posterior white commissure, the habenular commissure, the tectorial lamina, and the choroid plexuses.Features. It regulates the circadian rhythms of hormonal secretions, mainly linked to the light and dark cycles. It also has an influence on the gonadal sphere (testicles and ovaries) and is also responsible for secreting melatonin.

Thalamus

Structure. It is divided into anterior thalamus, medial thalamus and lateral thalamus. The latter in turn contains a dorsal region, a ventral region and the metathalamus.Function. It works as a relay between cortical and subcortical connections. It is a recipient of sensory input, except for olfactory input, which reaches the cortex directly. In addition, it intervenes in the regulation of consciousness and the sleep cycle.

subthalamus

Structure. It is composed of the subthalamic nucleus of Luys, the zona incerta, the prerubric field of Forel, the globus pallidus, and the dorsal compact and ventral reticular portions of the substantia nigra.Features. It participates in the regulation of movements and is related to the production of dopamine and therefore to the brain’s reward system.

hypothalamus

Structure. It is divided, from front to back, into the anterior, middle, and posterior hypothalamus. It contains a periventricular zone, a medial zone and a lateral zone.Features. It is the regulatory center of visceral functions through the vegetative and endocrine systems. In addition, it regulates emotional behavior through the limbic system, maintains homeostasis, and produces 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 allowing it to stay healthy.

Curious facts about the diencephalon

The diencephalon is that control center that makes our body maintain its internal balance or homeostasis. We show you some of its curiosities:

It only represents 2% of the total weight of the nervous system.The pituitary gland, which is attached to the hypothalamus and is involved in processes such as reproduction and growth through the action of hormones.Maintains body temperature.It regulates appetite and therefore food intake. The habenula, part of the epithalamus, is related to fear and depression.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 also participates in neuroendocrine responses to stress. In fact, in the magazine Dialogues in Neuroscience A published study appears about the relationship between the hypothalamic-pituitary-adrenal axis and stress. It is postulated that animals, to respond to stress, activate a range 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 comes to manage the situation by working together with the nervous, endocrine and immune systems.

In addition, The enormous importance of the hypothalamus in the generation of emotional behaviors has been demonstrated. For example, H. Nakao, in a study published in the journal American Journal of Physiology, found that stimulation of the hypothalamus in cats through implanted electrodes resulted in aggressive responses.

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

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