diencephalon i

Dr. Ahmed Fathalla Ibrahim

DIENCEPHALONDIENCEPHALON• ORIGIN:ORIGIN: from prosencephalon

• COMPONENTS: COMPONENTS: from dorsal to ventral: epithalamus, thalamus, subthalamus & hypothalamus

• CAVITY: CAVITY: third ventricle

EPITHALAMUSEPITHALAMUS• SITE: SITE: above superior colliculus,

dorsal to thalamus• COMPONENTS:COMPONENTS:1.1. Pineal gland: Pineal gland: secretes melatonin that

regulates onset of puberty2.2. Habenular nuclei: Habenular nuclei: a part of limbic

system

THALAMUSTHALAMUS

SHAPE: SHAPE: • An oval mass of grey matter• Both thalami are joined by

interthalamic adhesioninterthalamic adhesion

RELATIONS OF THALAMUSRELATIONS OF THALAMUS

THALAMUSTHALAMUSRELATIONS:RELATIONS:• Superior:Superior:1.1. Its lateral part Its lateral part is related to caudate nucleus2.2. Its medial part Its medial part forms the floor of lateral

ventricle• Inferior: Inferior: hypothalamus & subthalamus• Medial: Medial: forms the lateral wall of third

ventricle• Lateral: Lateral: posterior limb of internal capsule

separating it from lentiform nucleus

SUBDIVISIONS OF THALAMUSSUBDIVISIONS OF THALAMUS

CONNECTIONS OF THALAMUSCONNECTIONS OF THALAMUS

ANTERIOR GROUP OF NUCLEI:ANTERIOR GROUP OF NUCLEI:• A part of limbic system limbic system• Concerned with recent memory, recent memory,

emotion, behavioremotion, behaviorAnterior groupAnterior group Cingulate gyrusCingulate gyrus

HippocampusHippocampusMammillary bodyMammillary body

CONNECTIONS OF THALAMUSCONNECTIONS OF THALAMUS

MEDIAL GROUP OF NUCLEI:MEDIAL GROUP OF NUCLEI:• A part of limbic system limbic system• Concerned with control of mood & of mood &

emotionemotion

HypothalamusHypothalamus

Prefrontal cortexPrefrontal cortexMedial groupMedial group Prefrontal cortexPrefrontal cortex

CONNECTIONS OF THALAMUSCONNECTIONS OF THALAMUS

LATERAL GROUP OF NUCLEI:LATERAL GROUP OF NUCLEI:• Specific nucleiSpecific nuclei• Non specific nucleiNon specific nuclei

SPECIFIC NUCLEISPECIFIC NUCLEI

VENTRAL POSTERIOR:VENTRAL POSTERIOR:• VENTRAL POSTERIOR LATERAL (VPL)VENTRAL POSTERIOR LATERAL (VPL)• VENTRAL POSTERIOR MEDIAL (VPM)VENTRAL POSTERIOR MEDIAL (VPM)LATERAL GENICULATE BODY (LGB)LATERAL GENICULATE BODY (LGB)MEDIAL GENICULATE BODY (MGB)MEDIAL GENICULATE BODY (MGB)VENTRAL ANTERIOR (VA)VENTRAL ANTERIOR (VA)VENTRAL LATERAL (VL)VENTRAL LATERAL (VL)

SPECIFIC NUCLEISPECIFIC NUCLEI

Medial leminiscusMedial leminiscus

Spinal leminiscusSpinal leminiscusVPLVPL

Trigeminal leminiscusTrigeminal leminiscus

Taste fibresTaste fibres

VPMVPM

Sensory cortexSensory cortex

SPECIFIC NUCLEISPECIFIC NUCLEI

Optic tractOptic tract LGB LGB Visual cortexVisual cortex

Inferior Inferior MGB MGB Auditory cortex Auditory cortexcolliculuscolliculus

Globus Premotor &Globus Premotor &pallidus Motor cortexpallidus Motor cortex

VAVAVLVL

NON SPECIFIC NUCLEINON SPECIFIC NUCLEI

• LATERAL DORSALLATERAL DORSAL• LATERAL POSTERIORLATERAL POSTERIOR• PULVINARPULVINAR

They are connected to wide areas of They are connected to wide areas of cerebral cortexcerebral cortex

CONNECTIONS OF THALAMUSCONNECTIONS OF THALAMUS

INTRALAMINAR NUCLEUS (IL):INTRALAMINAR NUCLEUS (IL):• Control all level of activities of cerebral

cortex

Reticular formationReticular formation

Specific thalamic nucleiSpecific thalamic nucleiILIL All cortical areasAll cortical areas

CONNECTIONS OF THALAMUSCONNECTIONS OF THALAMUS

RETICULAR NUCLEUS (RN):RETICULAR NUCLEUS (RN):• Control mechanism of cerebral cortex

over thalamus

All cortical areasAll cortical areas RNRN All thalamic nucleiAll thalamic nuclei

THALAMIC LESIONTHALAMIC LESION

THALAMIC SYNDROME:THALAMIC SYNDROME:• Contralateral hemianaesthesiaContralateral hemianaesthesia• Occurrence of spontaneous painOccurrence of spontaneous pain• Contralateral hemiparesisContralateral hemiparesis• ChoreoathetosisChoreoathetosis