Diencephalon – Diencephalon
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Central nervous system
The diencephalon is a group of nuclei surrounding the third ventricle and connects the brainstem with the telencephalon. It is involved in processing of somatosensory, special sensory and motor information. According to the distribution and function of particular nuclei, the diencephalon is divided into six parts. The main structure involved in integration and interconnection of afferent (sensory) information is the thalamus. The hypothalamus represents a part of the diencephalon involved in regulation of the autonomic and endocrine system. Ontogenetically, the diencephalon is derived from the prosencephalon which also represents the developmental base for the telencephalon. Topography
• 1 Rostrally: optic chiasma • 2 Rostrally: frontal lobe • 3 Caudally: midbrain • 4 Medially: third ventricle • 5 Laterally: internal capsule • 6 Laterally: basal nuclei • 7 Basally: cranial base • 8 Dorsally: corpus callosum • 9 Dorsally: septum pellucidum
Darkness stimulates melatonin production (its level increases during night).
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Luys´ body (corpus Luysi) is an obsolete term for the subthalamic nucleus.
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Zona incerta means an uncertain zone because its exact function is still not sufficiently explained
Frontal section of the brain
The hypothalamic sulcus is derived from the sulcus limitans, and the third ventricle represents an enlargement of the central canal.
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The metathalamus forms the dorsal part of the thalamus containing the auditory medial geniculate body (corpus geniculatum mediale) and the visual lateral geniculate body (corpus geniculatum laterale).
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Sagittal section of the brain
Frontal section of the brain
Division
• 1 Thalamus
– interconnection of afferent pathways to the cortex 2 Metathalamus – the dorsal part of the thalamus containing the nuclei of the visual and auditory tracts 3 Hypothalamus – a control centre of autonomic and endocrine functions 4 Epithalamus – its main part is the pineal gland 5 Subthalamus – nuclei and tracts involved in motor and emotional neuronal patterns 6 Thalamus opticus – the basal part containing a part of the optic nerve, chiasma, and optic tract
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Development
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Sagittal section of the brain
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1 Somatosensory and sensory parts of the diencephalon 2 – thalamus, metathalamus and epithalamus 5 – are derived from the alar plate – are located above the hypothalamic sulcus Motor parts of the diencephalon Brainstem and diencephalon, – hypothalamus and subthalamus lateral view – are derived from the basal plate – are situated below the hypothalamic sulcus
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Habenula is a Greek term meaning a bridle, because the stria medullaris of thalamus resembles the reins in the area of the habenular trigones. The H fields (Haubenfelder) are named according to the parable with a German helmet with a crest. Forel´s field H is formed by a fusion of the ansa lenticularis and lenticular fascicle.
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Synonyms for pineal gland (glandula pinealis) are: pineal body or epiphysis cerebri.
Frontal section of the brain
The stria medullaris thalami contains fibers from the amygdaloid body, hippocampal formation, hypothalamus, septum verum, preoptic area, and olfactory tubercle. From the developmental point of view, the diencephalon consists of the rostral diencephalon and the caudal diencephalon. The rostral diencephalon consists of the hypothalamus. The caudal diencephalon consists of the pretectum (including the pretectal area), the posterior commissure, thalamus (including the epithalamus, metathalamus prethalamus, zona incerta, reticular nuclei of the thalamus and the subthalamus with the subthalamic nucleus). The preoptic area is considered to be a separate part.