HYPOTHALAMUS ANATOMY.pptx

HYPOTHALAMUS

1. HYPOTHALAMUS ANATOMY Dr B Vinod Mch Neurosurgery Resident Gandhi medical college Hyderabad

2. The diencephalon is divided into two major parts: pars dorsalis and pars ventralis . These subdivisions are seen in midsagittal view of the brain and are separated from each other by a shallow groove, the hypothalamic sulcus , which extends from interventricular foramen to the rostral end of the cerebral aqueduct of the midbrain

3. HYPOTHALAMUS Part of the diencephalon which lies below the thalamus. It extends from optic chiasma to caudal end of mammillary body. It forms the floor &lateral border of 3 rd ventricle. Anatomically, hypothalamus is small in size weighing only 4 g and forming only 0.3% of the total brain mass, but physiologically there is hardly any activity in the body that is not influenced by it. Thus, the functional significance of hypothalamus is disproportionate to its size. Controls the autonomic and endocrine systems.

4. BOUNDARIES Anteriorly : Lamina terminalis (lamina terminalis extends from the optic chiasma to the anterior commissure). Posteriorly: Subthalamus. Inferiorly : Structures in the floor of the 3rd ventricle, viz. tuber cinereum, infundibulum and mammillary bodies. Superiorly: Thalamus. Laterally: Internal capsule. Medially : Cavity of the 3rd ventricle.

5. SUB-DIVISIONS Subdivided antero-posteriorly into the following four regions: 1.Preoptic region—adjoining the lamina terminalis. 2.Supraoptic region—above the optic chiasma. 3.Tuberal region—includes the tuber cinereum, infundibulum and area around it. 4.Mammillary region—includes the mammillary bodies and area around it.

6. Hypothalamic Nuclei

7. Pre-optic : medial – GnRH, Lateral- sleep promoting area Supraoptic – Releases ADH Paraventricular- Oxytocin, Anterior – Body temperature , sweating. sexual behavior , stimulate PNS

8. Tuberal region Infundibular – Neuroendocrine Dorsomedial- GI stimulation Ventromedial- Satiety centre . Lateral – Hunger and thirst.

9. MAMILLARY REGION Mammillary body- feeding reflexes,papez circuit , wake promoting area Posterior nucleus- stimulate sympathetic (Increase BP, Pupillary dilatation & shivering.)

10. Connections of Hypothalamus

11. Functions of Hypothalamus Endocrine ANS Reproduction Temperature Thirst and hunger Food intake Emotion Circadian rhythm

12. Control of Anterior pituitary TRH CRH GHRH GnRH PIH

13. Control of Posterior pituitary

14. Hormones leave axons of tract and absorbed into bloodstream in the capillaries of posterior lobe. Carried by protein – Neurophysin

15. Control of ANS Paraventricular nuclei via medial forebrain bundle to dorsal brainstem and periaqueductal gray area, To synapse with the preganglionic sympathetic cells in the lateral horns of the thoracic and upper two lumbar spinal segments and with the preganglionic parasympathetic cells in the lateral horns of the S2, S3, and S4 s pinal segments to form hypothalamospinal tract .

16. LIMBIC PATHWAY Connected to hypothalamus via two pathways: Stria terminalis Ventral amygdalo fugal pathway. Related to emotional behavior

17. HUNGER AND FEEDING Feeding centre –lateral nucleus Stimulation increases appetite Lesion – starve and cachexia Satiety centre - ventro -medial nucleus Stimulated by glucose Stimulus suppresses appetite by inhibiting lateral nucleus Lesion -obesity

18. In diabetes mellitus (DM), ventro medial nucleus is deprived of glucose due to deficiency of insulin Increase activity of feeding centre results in hyperphagia Other factors which inhibit food intake are: Polypeptides Git hormones ( CCK,Glucagon,somatostatin ) Leptin (from fatty acids)

19. Regulation of Temperature Anterior nucleus Detects increase body temperature –dissipation of heat via vasodilation,sweating Lesion –hyperthermia Posterior nucleus Conserve heat by vasoconstriction & shivering Lesion – poikilothermia

20. Water intake and thirst By two mechanism : Osmoreceptors in supraoptic nucleus- are sensitive to osmolality changes in plasma. Excess water loss and dehydration ,causes increase osmolarity ,which stimulates osmoreceptors ,releases ADH, then water reabsorption Vice versa 2 . By thirst mechanism in lateral nucleus causes water drinking

21. Reproduction control Male –spermatogenesis, accessory organs growth Females- Ovulation & secondary sexual character

22. FROHLICH SYNDROME space occupying lesion ,secondary to anterior lobe pituitary . As tumor size increases ,pressure on hypothalamus increases Loss of control over ant. Lobe of pituitary, Leads to endocrine abnormality

23. Post head injury(UO ) Hypothalamus causes : production of ADH by supra optic nucleus decreased leads to DI 2 ) Post lobe damage .

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