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