HYPOTHALAMUS

2. HYPOTHALAMUS • The hypothalamus is a very small, but extremely important part of the diencephalon that is involved in the mediation of : • endocrine, • autonomic and • behavioural functions.

3. General information • Part ofdiencephalon • Weighs about 4 grams The whole brain weighs 1 400 grams • Occupies the bottom and infero-lateral wallsof the 3rd ventricle

4. The Diencephalon

5. thalamus hypothalamus Epithalamus (Pineal & Habenula) Optic chiasm pituitary Mammillary body subthalamus The Diencephalon fornix

6. Hypothalamus Hypothalamic sulcus Anterior commissure Lamina terminalis Mamillary body Optic chiasma

7. Hypothalamus 3.Superiorly:hypothalamic sulcus Position: lies ventral to thalamus Boundaries Anteriorly: Lamina terminalis 2. Posterior: continues with midbrain tegmentum i iii ii 4. Inferiorly: i. optic chiasma,ii. tuber cinereum, infundibulum,and iii. mamillary body

8. Organization In the sagittal plane, it is customary to divide the hypothalamus into three regions: These are from medial (3rd Vent.) to lateral: Periventricular, Medial, and Lateral In the coronal plane, the hypothalamus can be divided into: 1.Anterior (supraoptic), 2. Middle (tuberal), and 3. Posterior (mammillary). Since in a deep plane the structures in in the SO region extend beyond the lamina terminalis, therefore the preoptic region is also included in hypothalamus

9. Divisions of the Hypothalamus

10. Three rostral to caudal regions are distinguished in the hypothalamus that correspond to three prominent features on its ventral surface: 1) The supraopticor anterior region at the level of the optic chiasm, 2) the tuberal or middle region at the level of the tuber cinereum (also known as the median eminence—the bulge from which the infundibulum extends to the hypophysis), and 3) the mammillary or posterior region at the level of the mammillary bodies

11. Chiasma opticum Infundibulum (median eminence) Tuber cinereum Mamillary body Optictract Hypothalamus 1 2 3 Ventral view

13. Medial Zone Lateral Zone Preoptic, Supraoptic, Suprachiasmatic, Anterior, Paraventricular Anterior chiasmatic Dorsomedial Ventromedial Arcuate Nucleus Middle Tuberal Fornix 3rd Ventricle Periventricular zone Medial Forebrain Bundle Posterior Mamillary Caudal Mammilary

16. Hypothalamic Connections • Receives indirect sensory inputs from all sensory systems • Sends neural outputs to various motor control nuclei • Sends neural outputs to sympathetic and parasympathetic nervous systems • Sends both neural and hormonal outputs to pituitary

17. MAJOR CONNECTIONS OF HYPOTHALAMUS LIMBIC SYSTEM 1.MEDIAL FOREBRAIN BUNDLE septal nuclei, olfactory regionsHYPOTHALAMUS & brain stem  2. FORNIX Hippocampal Complex Mammillary Bodies of Hypothalamus  3. STRIA TERMINALIS Amygdala Hypothalamus 4.MAMMILLOTHALAMIC TRACT HypothalamusThalamus (anterior nucleus)

18. AUTONOMIC CONNECTION  5. DORSAL (posterior) LONGITUDINAL FASCICULUS Hypothalamus Brain Stem Reticular Formation Hypothalamus Brain Stem Nuc (e.g. Vagus) Intermediolateral Cell Column ENDOCRINE CONNECTIONS 6.HYPOTHALAMOHYPOPHYSIAL TRACT Hypothalamus Neurohypophysis  7.Tuberoinfundibular Tract Tuberal Nuclei Sinusoids, Portal VeinsAdenohypophysis

20. Hypothalamus Functions

21. Neural Influences Hormonal Influences Autonomic Nervous System Endocrine System Limbic System The Hypothalamus

22. Functions of the Hypothalamus • Autonomic nervous system regulation • Hormone production • Endocrine regulation • Circadian rhythm regulation • Limbic system interaction • Various • Temperature regulation • Feeding

23. Functions of the Hypothalamus • Autonomic nervous system regulation • Anterior area influences PSNS through projections to brainstem PSNS nuclei • Posterior area influences SNS through projections to the lateral gray horn

24. Functions of the Hypothalamus • Hormone production • Supraoptic and paraventricular nuclei produceoxytocin and vasopressin (ADH) • Transported via axonal transport systems (hypothalamohypophysial tract) to neurohypophysis • Released in circulation • Clinical Correlate • Damage to supraoptic n.  diabetes insipidus

25. Functions of the Hypothalamus • Endocrine regulation • Stimulating or inhibiting hormones are transported via the tuberoinfundibular tract and released in to the pituitary portal system and ultimately to the adenohypophysis

26. Functions of the Hypothalamus • Circadian rhythm regulation • Input from retina to suprachiasmatic nucleus is then sent through poorly defined projections to the pineal gland

27. Functions of the Hypothalamus • Limbic system interaction • Preservation of species • securing food, defense mechanisms, sexual behavior • Emotions • Affective behavior • Memory • Motivation • Mammillary body

28. Functions of the Hypothalamus • Various • Temperature regulation • Feeding • Temperature • Posterior n. conserves heat • Anterior n. dissipates heat • Fever starts – sweating • Fever ends – chills • Feeding • Lateral n. induces eating • Ventromedial n. inhibits eating

29. ADENOHYPOPHYSIS Connected with the hypothalamus via the hypophyseal portal system NEUROHYPOPHYSIS Connected with the hypothalamus via the hypophyseal tract

30. Tubero-infundibular tract

31. Posterior Pituitary Hormones Antidiuretic hormone (ADH) orvasopressin and Oxytocin synthesized primarily in the supraoptic nuclei & Paraventricular nuclei of the hypothalamus Hypothalamohypophysial tract

32. Anterior ( Supraoptic ) Region

33. Middle or Tuberal DorsomedialNucleus -center of satiety -on stimulationrage, cruelty Ventromedial Nucleus -center of satiety -on stimulation depression of appetite Arcuate Nucleus -periventricular intuber cinereum -secretesreleasing-factors -dopaminergic neurons inhibit release ofprolactin

34. Posterior or Mamillary Region Mamillary Nucleus -impulses fromhippocampal formationviafornix -impulses fromtegmental nuclei, nuclei raphaeviamamillarypeduncle -projections toanterior thalamic nucleusviamamillothalamic peduncle Nucleus posterior -controlsthermoregulation(preserving temperature and producing heat) -damage causespoikilothermia–inability ofthermoregulation

35. Lateral zone Crossed byMedial forebrain bundle Contains two nuclei: 1. lateral preopticNucleus 2. lateral hypothalamicNucleus Clinical Correlate - when stimulated feeling of hunger - when destroyedanorexia nervosa and fast

36. Neurotransmitters in the Hypothalamus • The hypothalamus has been referred to as a “pharmacological museum” by virtue of the plethora of neurotransmitters that it contains. • The list of putative neurotransmitters includes: • ACh, • GABA, • glutamate, • serotonin, • dopamine, and • norepinephrine as well as literally dozens of peptides that have been identified in recent years.

37. SUMMARY Dorsomedial

38. MAJOR FIBER TRACTS OF HYPOTHALAMUS

40. Lesion of lateral hypothalamic area leads to starvation Lesions of VMN leads to morbid obesity

41. The hypothalamus is supplied with blood by small branches of the Circle of Willis

43. Diabetes Insipidus Damage to the anterior hypothalamus blocks the production of ADH, resulting in diabetes insipidus, which is characterized by rapid water loss from the kidneys.

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