From interventricular foramen to posterior [619459]

Diencephalon
• From interventricular foramen to posterior
commissure
• Divisible in to:
ThalamusHypothalamusSubthalamusEpithalamusMetathalamus

Thalamus
• Large mass of grey matter, lateral to 3rdventricle.
• Processes the affarent impulses to cerebral cortex.• Reciprocal connections with cerebral cortex & subcortical
grey masses.
• Anterior & posterior ends• Surfaces: Medial – lined by ependyma; forms lateral wall
of third ventricle; interthalamic adhesion; hypothalamic sulcus
Superior – anterior tubercle; related to fornix, stria
terminalis, caudate nucleus.
Inferio r- related to hypothalamus anteriorly, to
subthalamus posteriorly; post. Surface exhibits two swellings- MGB & LGB.
Lateral – in contact with internal capsule.

Thalamus- internal structure
• Stratum zonale
• External medullary lamina• Internal medullary lamina- divides it in to
Anterior – anteroventral, anterodorsal,
anteromedial
Medial – Dorsomedial
Lateral- Dorsal- lateral dorsal, lat. Posterior,
pulvinar
Ventral- ventral anterior, ventral lateral,
ventral posterior

Thalamic nuclei-contd.
• Midline nuclei- closely associated with
interthalamic adhesion; concerned with visceral activity; connected to hypothalamus, dorsomedian & to intralaminar nuclei.
• Intralaminar nuclei- separate medial & lateral
nuclei. Main nuclei-centro median, parafascicular;
affarents from reticular formation, fore brain, pallidal; efferent to putamen.

•Anterior nucleus :
Mamillary body ANcingulate gyrus
(mamillothalamic tract)
•Dorsomedial nucleus :
Amygdaloid body DM cingulate gyrus, parietal
lobe, prefrontal cortex
Globus pallidus piriform lobe

Ventral group
•Ventral anterior : Globus pallidus VAPremotor & motor c. cortex
•Ventral lateral- sub. nigra, GP, precentral C.C VMprecentral C. C.
•Ventral Posterior : Ventral Posteromedial (VPM )
(largest somatic relay) Ventral posterolateral (VPL )
Medial lemniscus VPLSup. Thalamic radiations Sensory C. Cortex
(3,1,2)Spinothalamic tract VPL ( post. Limb of Int. capsule)
Trigemino-thalamic
Solitariothalamic VPMSensory Cerebral Cortex (3,1,2)

Lateral Group
•Lateral dorsal
•Lateral posterior
•Pulvinar
Superior colliculus LD, LP, P  sup. Parietal lobule, cingulate
gyrus, parahippocampal &
hippocampus, Parietal area
Retina  P association visual area

Afferent connections
1. Spinothalamic tract
Medial lemniscusTrigemino-thalamicSolitariothalamic
2. Optic tract3. Auditory pathway4. Mamillothalamic tract5. Cerebellar fibres6. Corpus striatum &
globus pallidus
7. From cerebral cortex

Thalamic radiations
(efferent)
1. Anterior (frontal)2. Superior
(centroparietal)
3. Posterior
(occipital)
4. Inferior
(temporal)

Hypothalamus
• Below the thalamus, forms lower lateral wall of
3rdventricle.
• Laterally in contact with internal capsule &
subthalamus.
• Posteriorly merges with subthalamus.• Anteriorly extends up to lamina terminalis.• Inferiorly related to structures in floor of 3
rd
ventricle.
• Medial and lateral zones

Afferent connections
1. From spinal cord & brainstem (via reticular
formation)
2. Nucleus of tractus solitarius3. Olfactory pathways4. Limbic system5. Locus coeruleus6. From piriform cortex, orbital cortex7. From subthalamus & zona incerta

Efferent connections
1. To autonomic centres in brain stem and spinal cord e.g.
tractus soiltarius, dorsal nucleus of vagus, nucleus ambiguus, intermedio-lateral grey column.
2. To hippocampal formation, septal nuclei, amygdaloid
complex, tegmentum.
3. To anterior nucleus of thalamus (mamillothalamic tract)4. To subthalamus & tegmentum (mamillo-tegmental tract)5. To neocortex6. Control of pituitary gland
– neurosecretion
– release of vasopressin (ADH); oxytocin- control of post. Neurohypophysis- production of releasing factors (tubero-hypophyseal)- hypothalamo-hypophysial portal system

Functions
1. Regulation of eating & drinking behaviour
2. Regulation of sexual activity & reproduction3. Control of autonomic activity4. Control of endocrine system5. Emotional behaviour6. Response to stress7. Temperature regulation8. Biological clock

Epithalamus
• Visceral efferent pathway to convey
impulses to brain stem.
• Pineal body• Habenular trigone• Stria medullares

Pineal body
• Cone shaped body attached to roof of 3rdventricle
• Rudimentary gland• Richly vascular connective tissue along with glia cells and
pineal cells.
• Receives fibres from stria medullares, habenular nuclei &
post. Com.
• Inhibits gonadal function.• After 16 yrs., calcerous bodies present which are visible in
skull x-rays.
• Identification & position of pineal gland in skull films.

Metathalamus
• Medial geniculate body
• Lateral geniculate body

Lateral geniculate body

Subthalamus
• Lies below post. part of thalamus
• Inferiorly continuous with tegmentum• Laterally related to internal capsule• Reticular nucleus: separated from thalamus.
somatic, visceral, auditory, reticular formation send afferents
to reticular nucleus which connects to dorsal part of thalamus.
• Zona incerta: connected to reticular nucleus; function not
known.
• Subthalamic nucleus: closely re lated to zona incerta on one
side and red nucleus on the other side. Subthalamic fasciculus pass to globus pallidus.

Applied anatomy
•Lesions of thalamus : sensory loss
thalamic painthalamic handabnormal involuntary movements
•Subthalamic lesions : sudden, forceful, jerky/violent involuntary
movements in a contralateral extremity.
•Pineal body : pineal tumors result in alteration of reproductive
function.
•Hypothalamus : Obesity/wasting
Sexual disordersHypo/hyperthermiaDiabetes insipidusDisturbance in sleepEmotional disorders