The Diencephalon
SHANDONG UNIVERSITY
Liu Zhiyu
Position of Diencephalon
Position: Lies between midbrain and cerebrum, almost entirely surrounded by cerebral hemisphere
Diencephalon
Subdivision of Diencephalon
Doral thalamus Metathalamus Epithalamus Subthalamus Hypothalamus
Dorsal Thalamus
Dorsal Thalamus
External features A large egg-shaped nucleus
mass Anterior end - anterior thala
mic tubercle Posterior end - pulvinar Right and left portion of thala
mus are joined by interthalami
c adhesion Floor - hypothalamic sulcus
Classification of Nuclei of Dorsal Thalamus
Three nuclear group- divided by internal medullary lamina
Anterior nuclear group Medial nuclear group Lateral nuclear group
Med. nuclear group Ant. nuclear group
Lateral nuclear group
Internal medullary lamina
Ventral anterior nucleus
Ventral lateral nucleus
Ventral posterolateral (VPL)
Ventral posteromedial (VPM )
Medial geniculate body (MGN)
Lateral geniculate body (LGN) Ventral posterior nucleus (VP)
Subdivision Principal Nuclei Common abbreviation
Ant. nuclear group
Med. nuclear group
Lat. nuclear group
Dorsal tier of the nuclei
Lateral dorsal LD
Lateral posterior LP
Pulvinar
Ventral tier of the nuclei
Ventral anterior VA
Ventral lateral VL
Ventral posterior VP
Ventral posterolateral VPL
Ventral posteromedial VPM
Functional Subdivision of Dorsal Thalamus
Nonspecific relay nuclei - receive afferents from rhinencephalon and reticular formation of brain stem, project mainly to hypothalamus and corpus striatum
Midline nucleus group Intralaminar nuclear group Thalamic reticular nucleus
Association nuclei - receive input from many converging sours and in turn project widely to the association areas of cerebral cortex
Anterior nuclear group Medial nuclear group Dorsal tier of lateral nuclear group
Functional Subdivision of Dorsal Thalamus
Special relay nuclei Vent. anterior nucleus (VA) Vent. intermediate nucleus (VI) Receiving dentate nucleus, globus pallidus and substantia nigr
a to motor cortex Vent. posteromedial nucleus (VPM ) ★ Receives trigeminal lemniscus and taste fibers
Vent. posterolateral nucleus (VPL ) ★ Receives medial lemniscus and spinal lemniscus
Projects to first somatic sensory area via central thalamic radiation
Metathalamus
Lateral geniculate body (LGN)
Medial geniculate body (MGN)
Metathalamus Medial geniculate body (M
GN) ★ Relay station of audition Receive fibers from inferior
colliculus Projects to auditory area via
acoustic radiation Lateral geniculate body (L
GN) ★ Relay station of vision Receive fibers from optic tra
ct Projects to visual area via o
ptic radiation
Epithalamus
Consist of: Thalamic medullary stria Habenular trigone Habenular commissure Pineal body posterior commissure
Subthalamus
Position: transition zone bet
ween diencephalons and tegm
entum of midbrain
Content: subthalamic nucle
us, parts of red nucleus and su
bstantia nigra
Hypothalamus
Position - lies ventral to thalamus
Boundaries
Superiorly: hypothalamic sulcus
Inferiorly:
optic chiasma
tuber cinereum
Infundibulum
mamillary body
Anterior: lamina terminalis
Posterior: continues with midbrain
tegmentum
Hypothalamus
Subdivisions Preoptic region Supraoptic region Tuberal region Mamillary region
Important Nuclei of Hypothalamus
Supraoptic region Supraoptic nucleus- produce antidiuretic hormone
(ADH , vasopressin) Paraventricular nucleus - produce oxytocin Tuberal
region Infundibular nucleus Ventromedial nucleus Dorsomedial nucleus
Mamillary region Mamillary nucleus Posterior hypothalamic nucleus
Paraventricular nucleus
Supraoptic nucleus
Paraventriculohypophyeal tract
Supraopticohypophyseal tract
infundibulum
posterior lobe of hypophysis
anterior lobe of hypophsis
Connections of Hypothalamus
Supraoptic nucleus → antidiuretic hormone (ADH) →supraopticoh
ypophyseal tract →posterior lobe of hypophysis
Paraventricular nucleus → produce oxytocin (oxytocin) →paravent
riculohypophyseal tract→posterior lobe of hypophysis
Parvicellular neurons in the arcuate nucleus and nearby region of th
e walls of the third ventricle secrete releasing and inhibiting hormon
es → tuberoinfundibular tract →portal vein of hypophysis → anterior
lobe of hypophysis
Paraventricular nucleus
Paraventriculohypophyseal tract
Supraoptic nucleus
Supraopticohypophyseal trac
posterior lobe of hypophysis
Inferior hypophyseal a.
Hypophyseal v.
Tuberoinfundibular tract
Median eminence
Portal v.
Superior hypophyseal a.
Hypophyseal v.anterior lobe
Parvicellular neurons in the arcuate nucleus and nearby region of the walls of the third ventricle secrete releasing and inhibiting hormones → tuberoinfundibular tract →portal vein of hypophsis → anterior lobe of hypophsis
Connections of Hypothalamus
Connects with limbic system Connects with brainstem and spinal cord Connects with dorsal thalamus Connects with hypophysis
Functions of Hypothalamus
Autonomic control Endocrine control Temperature regulation Regulation of food and water intake Emotion and behavior Control of circadian rhythms
Third ventricle
Position: a narrow ventricle cleft lies within diencephalons
Boundaries Roof: choroids plexus Floor:
optic chiasma tuber cinereum infundibulum and mamillary body
Anterior: lamina terminalis Posterior: continuous with mesencephalic aqueduct Lateral wall: dorsal thalamus and hypothalamus
Communication Third ventricle →mesencephalic aqueduct → fourth ventricle