Hypothalmamus and limbic system

By

Dr Manah Chandra Changmai

The hypothalamus consists of only 4 cm3 of neural tissue, or 0.3% of the total brain.

The hypothalamus extends from the lamina terminalis to a vertical plane posterior to the mammillary bodies, and from the hypothalamic sulcus to the base of the brain beneath the third ventricle.

Hypothalamus

Hypothalamus

It lies beneath the thalamus and anterior to the tegmental part of the subthalamus and the mesencephalic tegmentum

Relations

Anteriorly:Extends upto lamina terminalis and merges with

olfactory Structures.

Posteriorly :Merges with ventral thalamus and through it to

the Tegmentum of midbrain.

Medial side:Forms the wall of the third ventricle below the

levelOf hypothalamic sulcus.

Laterally :Contact with the internal capsule

Inferiorly:Related to the structures of the third ventricle

Hypothalamus

Lamina terminalisMamillary body

Hypothalamic sulcusSeptum pellucidum

Pellucidum

Choroid plexus

Aqueduct

Interventricular foramen

Subdivisions of the hypothalamus

Divided into three zones

Periventricular zone Intermediate zone Lateral zone

The periventricular and intermediate zones are often described togetheras medial zone

The hypothalamus also divide anteropoateriorly into four regions

Preoptic-Adjoins lamina terminalis

Supraoptic(chiasmatic)-Lie above optic chiasma

Tuberal (infundibulotuberal)-includes infundibulum tubercinereum

Mamillary(posterior)-consists of mamillarybody andarea above it)

Hypothalamus

Medial Zone(Periventricular and intermediate)

Lateral Zone

Preoptic region Preoptic nucleus

Supraoptic region Paraventricular nucleusPeriventricular cell grpsSuprachiasmatic nucleusIntermediate cell group

Suprachiasmatic nucleus

Tuberal region Dorsimedial nucleusVentrimedial nucleusArcuate/infundibular nu.Premamillary nucleus

Lateral tuberal nucleus

Mamillary or posterior region

Posterior nucleus Tuberomamillarynucleus

Mamillary body Mamillary nuclei

Hypothalamus and nuclei within them

Hypothalamus

Hypothalamus

Connections of the hypothalamus

Hypothalamus is concerned withvisceral function

Connected to various parts of limbissystem,reticular formation,autonomiccentres in brainstem and spinal cord.

It also releases secretions into the bloodstream and into CSF.

Afferent connections

The hypothalamus recieves visceral(including Taste) through spinal cord and brainstem.

Afferents from nucleus of tractus solitarius tohypothalamus carry taste sensation.

Somatic afferents reach through collaterals of major ascending tract

Afferents from olfactory pathway and limbic system.anterior perforated substance,septal nucleiAmygdaloid complex,hippocampus,piriformcortex.

Hypothalamus

Limbic system

Neocortex

Thalamus

Ascending Somatosensorypathway

Visceral centresIn brainstem &Spinal cord.

Visual input

Cortico-hypothalamic fibres

Hypothalamus receive fibres from the cortex of the frontal lobe

Many fibres relay in the thalamus (medial dorsaland midline nuclei and reach hypothalamus through periventricular fibres

Efferent connections

The hypothalamus sends fibres to autonomicCentres in brain and spinal cord

In brainstem:-Nucleus of solitary tract -Dorsal nucleus of vagus -Nucleus ambigus -Parabrachial nucleus

Hypothalamus

Limbic system-Hippocampus-septal nuclei-Amygdaloid complex

Neocortex

Thalamus -From mamillary body

Visceral centre in Brainstem-nu. Of tractus solitary tract-Dorsal nu. Of vagus-nu. Ambogus-Parabrachial nu.

Spinal cord:Intermediolateral grey column

Neoendocrine influenceof hypophysis cerebri

Efferent connections of Hypothalamus

Control of hypophysis cerebri by hypothalamus

Neurons in some hypothalamic nuclei produceBioactive peptides discharged to neighbourhoodCapillaries(neurosecretion)

Control of neurohypophysis(posterior lobe)

-Vasopressin is secreted in supraoptic nuclei

-Oxytocin is secreted in paraventricular nucleus.

-Axons of the paraventricular nucleus descendsTowards the supraoptic nucleus and joins the axonFrom supraoptic nucleus as the paraventriculohypoPhyseal tract.

Axons of paraventriculo-hypophyseal tractjoin axons arising from supra-optic nucleusto form supraoptico-hypophyseal tract.

The axons of supraoptico-hypophyseal tract passdown into neurohypophysis where they branchand end in relation to capillaries and releasetheir secretion.

Together known as Hypoyhalamo-hypophyseal tract

Paraventicular nucleus

Hypophysis cerebri

Supraoptic nucleusParaventriculo-

Hypophyseal tract

Supraoptico-hypophysealtract

Control of hypophysis cerebri by hypothalamus

Control of hypophysis cerebri by hypothalamus

Control of adenohypophysis by hypothalamus

Hypothalamus control adenohypophysis byProducing number of releasing factors.

Releasing factors travel through tubero-hypophyseal tract which recieves fibresfrom various nuclei.

Release the factors into the capillaries

The capillaries carry the factors into thepars anterior of hypophysis cerebri throughhypothalamo-hypophseal portal system.

Paraventricular nucleus

Hypophysis cerebri

Supra-chiasmatic nucleus

Limbic system

Fibres frombrainstem

Tubero-infundibular tract

Limbic system

Limbic system

Limbic system,in the past are believed to play an important role in the control ofvisceral activity

The areas of cerebral cortex in the regionare often refereed to as LIMBIC LOBE

Areas forming the limbic cortex

Hippocampus (ammon’s horn ) and dentate gyrus

Entorhinal cortex

Gyrus cinguli and paraterminal gyrus

Part of the parahippocampal gyrus

The indisium griseum ( regarded as vestigial part of limbic cortex)

The amygdaloid nuclei

Fibres bundles related to the limbic system

1.Olfactory nerves,tract and striae

2.Fornix

3.Stria terminalis

4.Stria medullaris thalami

5.Diagonal band

6.Anterior commissure

Anterior commissure

Amygdaloid nuclear complex-The region is called amygdaloid body or amygdala. -Situated near the temporal pole of cerebral hemisphere.-Lie in close relation to anterior end of inferior horn of lateral ventricle.-The lower end of stria terminalis lie in relation to amygdaloid complex.

Septal region-Masses of grey matter lie immediately anterior to lamina terminalis and the anterior commissure.

-Continous inferiorly with diagonal band

-superiorly with indusium griseum.

-Related specially to hippocampus and to hypothalamus.

Septal region

Hippocampal formation-Develops in relation to medial surface of cerebral hemisphere-C shaped in accordance with outline of body and inferior horn of the ventricle.-Underdeveloped thin layer of grey matter lining the upper surface of corpus callosum is called INDUSIUM GRISEUM-Dendate gyrus present in relation to inferior horn of lateral ventricle.

Hippocampus

Fibre bundles of limbic system

Stria teminalis-Related to inferior horn and central part ofThe lateral ventricle-It begins in amygdaloid complex and runs backwards in the roof of the inferior horn-It terminates near interventricular foramen and anterior commissure by dividing into various bundle.

Anterior commissure-Situated in the anterior wall of the third ventricle at the upper end of lamina terminalis

The Fornix-Made up of fibres arising from hippocampus-Body of the fornix suspended from corpus callosum by septum pellucidum-Posteriorly,divides into two crura.-The crura are interconnected by fibres passing from one another forming hippocampal commissure.

Anterior commissure

Fornix Septum pellucidum

Fornix

• The hypothalamus and limbic system helps regulate five basic physiological needs:1) Controls blood pressure and electrolyte

(drinking and salt appetite).2) Regulates body temperature through influence

both of the autonomic nervous system and of brain circuits directing motivated behavior (e.g. behavior that seeks a warmer or cooler environment).

3) Regulates energy metabolism through influence on feeding, digestion, and metabolic rate.

4) Regulates reproduction through hormonal control of mating, pregnancy and lactation.

5) Directs responses to stress by influencing blood flow to specific tissues, and by stimulating the secretion of adrenal stress hormones.

Thank you