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Dr. Ahmed Fathalla Ibrahim DIENCEPHALON • ORIGIN: from prosencephalon • COMPONENTS: from dorsal to ventral: epithalamus, thalamus, subthalamus & hypothalamus • CAVITY: third ventricle EPITHALAMUS • SITE: above superior colliculus, dorsal to thalamus • COMPONENTS: 1. Pineal gland: secretes melatonin that regulates onset of puberty 2. Habenular nuclei: a part of limbic system THALAMUS SHAPE: • An oval mass of grey matter • Both thalami are joined by interthalamic adhesion RELATIONS OF THALAMUS THALAMUS RELATIONS: • Superior: 1. Its lateral part is related to caudate nucleus 2. Its medial part forms the floor of lateral ventricle • Inferior: hypothalamus & subthalamus • Medial: forms the lateral wall of third ventricle • Lateral: posterior limb of internal capsule separating it from lentiform nucleus SUBDIVISIONS OF THALAMUS CONNECTIONS OF THALAMUS ANTERIOR GROUP OF NUCLEI: • A part of limbic system • Concerned with recent memory, emotion, behavior Anterior group Cingulate gyrus Mammillary body Hippocampus CONNECTIONS OF THALAMUS MEDIAL GROUP OF NUCLEI: • A part of limbic system • Concerned with control of mood & emotion Hypothalamus Medial group Prefrontal cortex Prefrontal cortex CONNECTIONS OF THALAMUS LATERAL GROUP OF NUCLEI: • Specific nuclei • Non specific nuclei SPECIFIC NUCLEI VENTRAL POSTERIOR: • VENTRAL POSTERIOR LATERAL (VPL) • VENTRAL POSTERIOR MEDIAL (VPM) LATERAL GENICULATE BODY (LGB) MEDIAL GENICULATE BODY (MGB) VENTRAL ANTERIOR (VA) VENTRAL LATERAL (VL) SPECIFIC NUCLEI Medial leminiscus VPL Spinal leminiscus Sensory cortex Trigeminal leminiscus VPM Taste fibres SPECIFIC NUCLEI Optic tract Inferior colliculus Globus pallidus LGB Visual cortex MGB Auditory cortex VA VL Premotor & Motor cortex NON SPECIFIC NUCLEI • LATERAL DORSAL • LATERAL POSTERIOR • PULVINAR They are connected to wide areas of cerebral cortex CONNECTIONS OF THALAMUS INTRALAMINAR NUCLEUS (IL): • Control all level of activities of cerebral cortex Reticular formation Specific thalamic nuclei IL All cortical areas CONNECTIONS OF THALAMUS RETICULAR NUCLEUS (RN): • Control mechanism of cerebral cortex over thalamus All cortical areas RN All thalamic nuclei THALAMIC LESION THALAMIC SYNDROME: • Contralateral hemianaesthesia • Occurrence of spontaneous pain • Contralateral hemiparesis • Choreoathetosis
