Consisting of gray matter and white matter, epithalamus and subthalamus are connected to different brain areas: for example, they are connected to the nuclei of the base (pale globe, substantia nigra, ventral pale), to the brainstem, to the cerebral cortex, to the components of the system limbic and to the preoptic area.
The epithalamus is involved in the regulation of the sleep-wake cycle, the reward system, learning, pain processing, hunger, thirst, etc .; the subthalamus, on the other hand, collaborates with the nuclei of the base to regulate voluntary movements.
The diencephalon resides in the center of the brain, between the brain and the brainstem, and includes extremely important nerve components, such as the aforementioned thalamus, the hypothalamus, the epithalamus, the subthalamus, the epiphysis, the neurohypophysis and the third ventricle.
free of myelin), and portions of white matter (neurons presenting a myelin wrapping around their axon).Abenular nuclei
Made up of gray matter and located just above the thalamus, on the so-called trine of the abenula, i abenular nuclei they actually include two even elements (*): the medial abenular nucleus and the lateral abenular nucleus.
The medial abenular nucleus receives nerve fibers from the lateral nucleus of the hypothalamus and from the ventral pale, which is one of the so-called nuclei of the base belonging to the brain; instead, it projects nerve fibers in the direction of the ventral tegmental area (midbrain), of the substantia nigra (other nucleus of the base) and of the nuclei of the median and dorsal raphe (brainstem).
The abenular nucleus receives nerve fibers from the locus coeruleus (brainstem), from the septal nuclei (septum pellucidum), from the ventral tegmental area, from the area of Broca (frontal lobe) and from the preoptic area (hypothalamus); instead, it projects nerve fibers in the direction of the epiphysis and the interpeduncular nucleus (midbrain).
As the reader can notice, the abenular nuclei put the epithalamus in communication with different brain structures (eg brainstem, hypothalamus, etc.).
(*) Nota Bene: in anatomy, an organ or a structure is said to be equal when it is present in two copies, to the right and to the left of the hypothetical plane that separates the human body into two equal halves (sagittal plane).
Abenular commissure
Located in front of the epiphysis and composed of white matter, the abenular commissure it is the brain element that unites the abenular nuclei of the right half of the human body to the abenular nuclei of the left half of the human body.
The abenular commissure is an example of an encephalic commissure; all the encephalic commissures are formations of white matter having the task of uniting a structure or an even region of the brain.
Medullary stria
There medullary stria it is a paired bundle of nerve fibers afferent (ie incoming fibers) to the abenular nuclei of the epithalamus and coming from the septal nuclei and the lateral nucleus of the hypothalamus.
The medullary stria is, in fact, the element that connects the epithalamus to the limbic system.
Epiphysis
Located behind the third cerebral ventricle and morphologically similar to a pinecone, the "epiphysis it is an endocrine gland of 5-8 millimeters, present in the brain of all vertebrates.
The epiphysis has the task of secreting melatonin, the hormone that regulates the sleep-wake cycle during the day.
To know every aspect of the epiphysis, we recommend reading the dedicated article at this link.
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