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Diencephalon

Diencephalon. Hypothalamus. General information. Part of diencephalon Weighs about 4 grams The whole brain weighs 1 400 grams Occupies the bottom and infero -lateral walls of the III ventricle. Topography. In the center of the limbic system .

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Diencephalon

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  1. Diencephalon

  2. Hypothalamus

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

  4. Topography • In the center ofthe limbic system. • At the crossing ofnumerous nerve pathways. • Surrounded by thecircle of Willis.

  5. Boundaries Anterior Lamina terminalis Posterior Corpora mammillaria Dorsal Sulcus hypothalamicus Medial ІІІ стомахче Lateral Subthalamus&capsulainterna Ventral Chiasmaopticum, tuber cinereum, corpora mammillaria& neurohypophysis

  6. Anatomy • Chiasma opticum • Infundibulum • Tuber cinereum • Corpus mamillare • Tractus opticus

  7. Organization • Composed of lateral and medial zones divided byfornix. • Nuclei of the lateral zoneconcerned with feeding (center of hunger) and drinking (center of thirst). • Nuclei of the medial zone grouped in 3 regions:regio anterior, tuberalis and posterior.

  8. Хипоталамични области и ядра • Латерална област • Nucl. preopticus lateralis • Nucl. hypothalamicus lateralis • Медиална област • Regio preoptica • Nucl. preopticus medialis • Полово диморфично ядро • Regio supraoptica • Nucl. suprachiasmatis • Nucl. anterior • Nucl. paraventricularis • Nnucl. supraopticus • Regio tuberalis • Nucl. dorsomedialis • Nucl. ventromedialis • Nucl arcuatus • Regio mamillaris • Nucll. mamillares • Nucl. posterior

  9. Lateral zone Crossed byfasciculus prosencephalicus medialis Contains two nuclei: 1. Nucleus preopticus lateralis 2. Nucleus hypothalamicus lateralis • - when stimulated feeling of hunger • - when destroyedanorexia nervosa and fast

  10. Regio anterior

  11. Hypothalamus

  12. Regio tuberalis Nucleus dorsomedialis - center of hunger - on stimulationrage, cruelty Nucleus ventromedialis - center of satiety - on stimulation depression of apetite Nucleus arcuatus - periventricular intuber cinereum - secretesreleasing-factors - dopaminergic neurons, inhibit release ofprolactin

  13. Regio posterior Nucleus mamillaris - impulses fromhippocampal formationviafornix - impulses fromtegmental nuclei, nuclei raphae via pedunculus mamillaris - projections tonucleus anterior thalami viatractus mamillothalamicus Nucleus posterior - controlsthermoregulation (съхранение и образуване на топлина) - damage causespoikilothermia – inability ofthermoregulation

  14. Connections

  15. Connections Extensiveandcomplex, can be summarized in3 categories: • Connections with thelimbic system • Connections with thepituitary gland • Connections withsomatic and visceral nuclei

  16. 1)Fasciculus prosencephalicus medialis: visceral function 2) Tractus supraopticohypophysialis: neurosecretion3) Tractus tuberoinfundibularis: liberins&statins 4) Afferents fromcorpora mamillaria: visceral function 5) Efferents tobrainstem & spinal cord: autonomous function

  17. Connections

  18. Afferents - nucleus tractussolitarii – visceral information via vagus. - formatioreticularis –various information from spinal cord. - retina – to nucl. suprachiasmaticus. Circadian rhythm. - circumventricular organs – lacks blood-brain bareer. Control of substances isolated from the CNS, e.g., toxins. - limbic and olfactory system –controls behavior reactions.-intrinsic receptors, monitor temperature and water balance.

  19. Main afferents From most parts of brain. Most pathways are non-myelinated and small. Fasciculus prosencephalicus medialis • Fromarea septalis& area olfactoria lateralisto hypothalamic nuclei. • Integratesolfactionwithemotionsandfeeding. Stria terminalis • Fromcorpus amygdaloideum andarea septalistoregiopreopticaandnuclei hypothalamicianteriores. • Controls physiological response toemotions and sexual arousal. Fornix • Fromformatiohippocampalistocorpora mammillaria. • Integratesmemory, emotionsandvisceral reactions.

  20. Main efferents Fasciculus mammillothalamicus • Fromnucleimamillares to nucleus anterior of thalamus. • Creating and coding memory traces. Hypothalamo-reticular pathway • Connects the hypothalamus withparasympathetic and sympathetic nuclei.

  21. Efferents: To autonomous nervous system medulla: а) parasympathetic nucleus ofn. vagus б) cells projecting tosympathetic nucleiin the spinal cord. Control ofheart rate, vasoconstriction, digestion, sweating etc.. Endocrine signals to/throughpituitary gland а) axons to neurohypophysisto releaseoxitocin&vasopressin; б) releasing factors into the vessels ofadenohypophysis. Hypothcan control anyendocrine gland, changeblood pressure (vasopressin and vasoconstriction), body temperature, metabolism (TSH) and epinephrine level (ACTH).

  22. Hypothalamus = Homeostasis Blood pressure, temperature, waterand electrolyte balance, weightare maintained within optimal values.

  23. Controls • Autonomous, endocrine, emotionalandsomatic functions • Servesthree basic systems: • Autonomic nervous system • Endocrine system • Lymbic system • Maintainshomeostasisof the body

  24. Function 1. Autonomous control - anterior regionstimulates parasympathetic function - posterior regionstimulates sympathetic function 2. Thermoregulation - anterior regionmaintainsbogy temperature - posterior regionstimulatesproduction and preservingheat 3. Maintaining water balance а. Nucleus ventromedialis – center of satiety б. Nucleus hypothalamicus lateralis – center of hunger 4. Liberins and statins - produced from nucleus arcuatus - transported to theportal system ofadenohypophysis - control hormon production in the adenohypophysis

  25. Functional characteristics

  26. Subthalamus

  27. General characteristics • Vaguely delineated area betweenmidbrain, thalamus, hypothalamus, capsula internaand ІІІ ventricle. • Contains fibers andnuclear structures - zona incerta,nucleus subthalamicus, Forel fields, nuclei reticulares • Connected mainly with somatomotor functions

  28. Nuclear structures • Nucleus subthalamicus (Luys) • Well definedlying oncapsula interna • Rostral penetration ofsustantia nigra • Connected bilaterally withglobus pallidus • Nuclei reticulares • Small groupsand extensionsof cells • Zona incerta - continuation of nucleus reticularis thalami • FieldsH ofForel (prerubral): • H1 ofForel - betweenthalamus andzona inserta • H2 ofForel - betweennucl. subthalamicus andzona inserta

  29. Fibers A. Fasciculus thalamicus (inH1 field ofForel) • 1. Lemniscus medialis • 2. Tractus dentatothalamicus • 3. Tractus pallidothalamicus • 4.Bundle ofreticular fibers connecting brainstem with diencephalon B.Fasciculus lenticularis (inH2 field ofForel) • - Pallidothalamic fibersthroughcapsula interna C.Ansa lenticularis • - Fibers fromglobus pallidus (mainly pallidothalamic)beneath capsula interna • D. Fasciculus subthalamicus – bidirectionalfibers betweenglobus pallidus and nucleus subthalamicus

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