Hypothalmamus and limbic system By Dr Manah Chandra Changmai
The hypothalamus consists of only 4 cm 3 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
<ul><li>It lies beneath the thalamus and anterior to the tegmental part of the subthalamus and the mesencephalic tegmentum </li></ul><ul><li>Relations </li></ul><ul><li>Anteriorly: </li></ul><ul><li>Extends upto lamina terminalis and merges with olfactory Structures. </li></ul><ul><li>Posteriorly : </li></ul><ul><li>Merges with ventral thalamus and through it to the Tegmentum of midbrain. </li></ul><ul><li>Medial side: </li></ul><ul><li>Forms the wall of the third ventricle below the levelOf hypothalamic sulcus. </li></ul><ul><li>Laterally : </li></ul><ul><li>Contact with the internal capsule </li></ul><ul><li>Inferiorly: </li></ul><ul><li>Related to the structures of the third ventricle </li></ul>
Subdivisions of the hypothalamus Divided into three zones Periventricular zone Intermediate zone Lateral zone The periventricular and intermediate zones are often described together as 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 mamillary body and area above it)
Hypothalamus and nuclei within them Medial Zone (Periventricular and intermediate ) Lateral Zone Preoptic region Preoptic nucleus Supraoptic region Paraventricular nucleus Periventricular cell grps Suprachiasmatic nucleus Intermediate cell group Suprachiasmatic nucleus Tuberal region Dorsimedial nucleus Ventrimedial nucleus Arcuate/infundibular nu. Premamillary nucleus Lateral tuberal nucleus Mamillary or posterior region Posterior nucleus Tuberomamillary nucleus Mamillary body Mamillary nuclei
Connections of the hypothalamus Hypothalamus is concerned with visceral function Connected to various parts of limbis system,reticular formation,autonomic centres in brainstem and spinal cord. It also releases secretions into the blood stream and into CSF.
Afferent connections The hypothalamus recieves visceral(including Taste) through spinal cord and brainstem. Afferents from nucleus of tractus solitarius to hypothalamus carry taste sensation. Somatic afferents reach through collaterals of major ascending tract Afferents from olfactory pathway and limbic system. anterior perforated substance,septal nuclei Amygdaloid complex,hippocampus,piriform cortex. Hypothalamus Limbic system Neocortex Thalamus Ascending Somatosensory pathway Visceral centres In 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 dorsal and midline nuclei and reach hypothalamus through periventricular fibres Efferent connections The hypothalamus sends fibres to autonomic Centres 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 influence of hypophysis cerebri Efferent connections of Hypothalamus
Control of hypophysis cerebri by hypothalamus Neurons in some hypothalamic nuclei produce Bioactive peptides discharged to neighbourhood Capillaries(neurosecretion) Control of neurohypophysis(posterior lobe) -Vasopressin is secreted in supraoptic nuclei -Oxytocin is secreted in paraventricular nucleus. -Axons of the paraventricular nucleus descends Towards the supraoptic nucleus and joins the axon From supraoptic nucleus as the paraventriculohypo Physeal tract.
Axons of paraventriculo-hypophyseal tract join axons arising from supra-optic nucleus to form supraoptico-hypophyseal tract. The axons of supraoptico-hypophyseal tract pass down into neurohypophysis where they branch and end in relation to capillaries and release their secretion. Together known as Hypoyhalamo-hypophyseal tract Paraventicular nucleus Hypophysis cerebri Supraoptic nucleus Paraventriculo- Hypophyseal tract Supraoptico-hypophyseal tract Control of hypophysis cerebri by hypothalamus
Control of adenohypophysis by hypothalamus Hypothalamus control adenohypophysis by Producing number of releasing factors. Releasing factors travel through tubero- hypophyseal tract which recieves fibres from various nuclei. Release the factors into the capillaries The capillaries carry the factors into the pars anterior of hypophysis cerebri through hypothalamo-hypophseal portal system. Paraventricular nucleus Hypophysis cerebri Supra-chiasmatic nucleus Limbic system Fibres from brainstem Tubero-infundibular tract
Limbic system Limbic system,in the past are believed to play an important role in the control of visceral activity The areas of cerebral cortex in the region are 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.
Fibre bundles of limbic system Stria teminalis -Related to inferior horn and central part of The 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
<ul><li>The hypothalamus and limbic system helps regulate five basic physiological needs: </li></ul><ul><ul><li>1) Controls blood pressure and electrolyte (drinking and salt appetite). </li></ul></ul><ul><ul><li>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). </li></ul></ul><ul><ul><li>3) Regulates energy metabolism through influence on feeding, digestion, and metabolic rate. </li></ul></ul><ul><ul><li>4) Regulates reproduction through hormonal control of mating, pregnancy and lactation. </li></ul></ul><ul><ul><li>5) Directs responses to stress by influencing blood flow to specific tissues, and by stimulating the secretion of adrenal stress hormones. </li></ul></ul>