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DIENCEPHALON II. Dr. Ahmed Fathalla Ibrahim. SUBTHALAMUS. SUBTHALAMUS. SITE: below thalamus, dorsolateral to hypothalamus COMPONENTS: Subthalamic nucleus: connected to globus pallidus (by subthalamic fasciculus) & to substantia nigra
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DIENCEPHALON II Dr. Ahmed Fathalla Ibrahim
SUBTHALAMUS SITE: below thalamus, dorsolateral to hypothalamus COMPONENTS: • Subthalamic nucleus: connected to globus pallidus (by subthalamic fasciculus) & to substantia nigra • Zona incerta (between thalamus & subthalamic nucleus): rostral extension of brain stem reticular formation • ROLE: control of voluntary movements
HYPOTHALAMUS SITE: • Below thalamus, separated from it by hypothalamic sulcus • Lies in the interpeduncularfossa (tuber cinereum, infundibulum, mammillary bodies) RELATION TO THIRD VENTRICLE: forms: • The lower part of lateral wall • Floor FUNCTION: regulator
HYPOTHALAMIC NUCLEI LATERAL HYPOTHALAMIC: “feeding center”: lesion aphagia MEDIAL HYPOTHALMIC: • Supraoptic: produces vasopressin • Paraventricular: produces oxytocin • Suprachiasmatic: controls diurnal rhythm • Anterior: stimulates parasympathetic system
HYPOTHALAMIC NUCLEI TUBERAL: • Ventromedial:“satiety centre”: lesionhyperphagia • Arcuate:produces releasing & release-inhibiting factors MAMMILARY REGION: • Mammillary: a part of limbic system • Posterior: stimulates sympathetic system
THE THIRD VENTRICLE CAVITY: of diencephalon COMMUNICATIONS: • With lateral ventricle:through interventricular foramen of Monro • With fourth ventricle:through cerebral acqueduct of Silvius
THE THIRD VENTRICLE BOUNDARIES: • ROOF: layer of ependyma covered by pia • FLOOR: hypothalmus • LATERAL WALL: • Upper part: thalamus • Lower part: hypothalamus • ANTRERIOR WALL: anterior commissure, lamina terminalis • POSTERIOR WALL: posterior commissure, pineal body