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Gustatory and olfactory apparatus and pathways.
Semmelweis University Department of Anatomy, Histology and Embryology 2nd year Kocsis Katalin
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Sensory pathways sensory homunculus Sensation: conscious
unconscious (spinocerebellar pathways) Conscious: - vision (50%)! hearing and balance touch, skin sensation - smell - taste „internal” sensation In human smell and taste sensation are less dominant sexual activity – feromons sensory homunculus
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Olfactory pathway: from the nasal cavity directly to the rhinencephalon
bilateral projection: localisation of the smell Gustatory pathway: to the thalamus cortex (Brodmann’s 43) afferent from the brain stem: visceral reflex response (like gastric juice production)
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Gustatory system
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Papillae circumvallatae
Gustatory system Papillae foliatae Papillae fungiformes
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Gemma gustatoria (taste buds)
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Forás: Röhlich Pál: Szövettan
porus gustatorius receptor supporting cells receptors supporting cells undifferentiated (basal or „stem” cells Receptors: dendrite-like short processes on the apical plasma membrane, stereocilia: chemoreceptors ( saliva and mucin). Life time: very short (10-60 days). Taste bud „stem” cells Schwann sheath afferent fibers basement membrane Forás: Röhlich Pál: Szövettan
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Signal transduction
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Four (five, six) basic tastes:
Saulty and sour: directly through the apical ion channels 1. Salty: – ions binding on the microvilli (inorganic ions) 2. Sour: – acids: protons (H+ ions) interact with microvilli Sweet and bitter: receptor-coupled „second messenger” pathway 3. Sweet – G-protein coupled, receptor-mediated transduction pathway; activation of adenyl cyclase → increase the level of cAMP; cAMP activates a PKA (protein kinase) → phosphorylation of the basolateral K+ channel → close → depolarization Ca-channels open 4. Bitter – IP3 (inozitol-3-phosphate) pathway → Ca2+ release New and candidate basic tastes 5. Umami (yammi, glutamate-rich) 6. ? Fatty (oily) / starch-taste
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Sensation of basic tastes, arrangement of specific taste buds
bitter sour salty sweet
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Sensation of basic tastes, arrangement of specific taste buds
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Sensory pathway of taste sensation
n. VII. chorda tympani n. IX. n. X. tongue anterior 2/3: (n. lingualis (V/3)) chorda tympani (n. VII) ganglion geniculi nucleus tractus solitarii tongue anterior 1/3: n. glossopharyngeus (rr. linguales) ganglion inferius nucleus tractus solitarii tongue root n. vagus (rr. linguales) ganglion inferius (nodosum) nucleus tractus solitarii
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Sensory pathway of taste sensation
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nucl. tractus solitarii (VII, IX, X) special visceroafferens
Brain stem nucleus nucl. tractus solitarii (VII, IX, X) special visceroafferens
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Cortical projection 43 n. tr. solitarii → thalamus VPM (parvicellular part VPM pc) → taste sensory cortex (lower part of the postcentral gyrus + operculum and inner surface of the insula (Brodman 43)
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Olfactory organ
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Smell sensation Bulbus olfactorius (CNS) Fila olfactoria
(lamina cribrosa) Forrás: Sobota - Atlas of Human Anatomy Liquor space of the CNS and the lymphatic vessels of the nasal cavity are in connection with each other through the lamina cribrosa: drugs can enter to the CNS by bypassing the blood/brain barrier
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Organum olfactum bulbus olfactorius tractus olfactorius
Thalamusban nincs átkapcsolás Primer bipoláris érzéksejtek axonjai (fila olfactoria): nervus olfactorius bulbus olfactorius tractus olfactorius Nagy konvergencia 1000:1 de nincs térképszerű megfeleltetés. Nincs „rózsillat-receptor”, minden glomerulus hozzájárul az észlelt szaghoz A primer érzéksejtek aktivitása változik, belégzés végén maximális, fokozza éhség, izgatottság, félelem
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Histological structure of the olfactory region
Tunica mucosa: lamina epithelialis: 3 types of cells: receptors: primary olfactory neurons; life time: days (only neurons known to proliferate during adult life) basal cells: proliferating cells; daughter cells differentiate into mature neurons supporting cells lamina propria: Bowmann‘s glands: odorant binding protein (OBP) regulation: parasympatetic (cholinergic – VIP fibers) sympathetic (ß-adrenergic fibers) Afferent fibers (from n. V.): (unmyelinated fibers, nerve endings) stimulation: local release of substance P: modifies the sensitivity of the neurons
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Olfactory region Receptors: primary sensory cells: bipolar cells
cilia cilia Receptors: primary sensory cells: bipolar cells contain OBP (odorant binding protein) receptors on their plasma membrane axon-like processes - fila olfactoria – bulbus olfactorius the number of them: 2 x 107 life time: days more than 100 receptor molecules bulb-like ending supporting cell receptor basal cells basement membrane Schwann cells axon
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Signal transduction Receptor:
individual receptors respond to large number of odorants and single odorant will stimulate large number of receptors each receptor contains many different receptor molecules olfactory receptor molecules have a broad spectrum of sensitivity and able to respond to many odorant G protein coupled, 7 transmembrane domain encoded by more than 1000 genes (in mouse) variable odorant binding sequences huge receptor „repertoir”
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Forrás: Szentagothai J, Réthelyi M: Funkcionális anatómia
olfactory epithelium olfactory glomerulus mitral cells tufted cells inhibitory granule cells Nucleus olfactorius anterior efferent fibers Forrás: Szentagothai J, Réthelyi M: Funkcionális anatómia medial lateral contralateral olfactory bulb L: prepiriform cortex (base of the frontal lobe, uncus), amygdala M: substantia perforata anterior, hypothalamus
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Olfactory bulb 6 layers: 1.) olfactorius n. fibers
2.) glomerular layer: periglomerular cells 3.) ext. plexiforme layer: processes of the mitral cells and tufted cells 4.) mitral cells layer 5.) inner plexiforme layer: granule cells 6.) central fiber core to olfactory tract
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Olfactory bulb: afferents
Primary afferents: olfactorius n. peptiderg (pl. carnosine) synapses with mitral, tufted and periglomerular neurons (convergence: about 1000 receptors to 1 mitral cell) Other afferents come: locus ceruleus (noradrenerg), reticular formation: raphe nuclei (serotononerg), medial septal nucleus (cholinerg), contralateral olfactory bulb Olfactory bulb: efferents Axons of the mitral cells: uncus, amygdala, ipsilateral olfactory cortex (glutamate, aspartate) Processes of the tufted cells: substantia perforata ant., contralateral olfactory bulb (substance P, dopamine, cholecystokinin, encephaline)
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Stria olfact. lateralis
Tractus olfactorius Trigonum olfactorium Stria olfact. lateralis Stria olfact. medialis bifurcate: lat.: sulcus lat. med.: limen insulae (anterior to the uncus) medial surface of the frontal lobe to subcallose area
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Olfactory cortex paleopallium (rhinencephalon) bulbus olfactorius
tractus olfactorius trigonum olfactorium striae olfactoria med. et lat. substantia perforata anterior Broca-féle diagonal band primer olfactory cortex (lobus piriformis): gyrus ambiens, gyrus semilunaris
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Central pathway from the olfactory bulb to the neocortical olfactory area
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hippocampus és amygdala
Connections of olfactory system gyrus cinguli fornix Complex pathway No connection with the thalamus! Projects to the most ancient cortical region. Strong relationship with the limbic system. Smell stimuli: regulate the basic emotional reactions. corpus mamillare hippocampus és amygdala
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Vomeronasalis organ (Jacobson's organ)
in the mucosa of the nasal cavity feromon-sensitive: sexual behaviour accessory olfactory bulb: amygdala „13th / 0th cranial nerve”: n. terminalis well developed in newborns in 60% of the adult population: regress
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References Röhlich Pál: Szövettan, SOTE Képzéskutató, Oktatástechnológiai és Dokumentációs Központ, Budapest, 1999 Szentagothai J, Réthelyi M: Funkcionális anatómia, Medicina, 1989 Sobota - Atlas of Human Anatomy, 20th edition, Urban and Schwarzenberger, 1993 Kahle: SH Atlasz Willis DW: The Special Senses in Berne RM et al.: Physiology, 5th edition, Elsevier Inc., 2004 Burt AM: Textbook of Neuroanatomy, Saunders Company 1993 Vígh B: Szisztémás anatómia, Rendszeres Orvosi Bonctan, Alliter, 2005
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