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The special senses

The special senses. Dpt. of Normal, Pathological and Clinical Physiology. CHAPTERS. hearing vestibular apparatus taste smell. HEARING. regular compression vawes transmitted in air (300m/s) , water (1500m/s) , and in a solid

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The special senses

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  1. The special senses Dpt. of Normal, Pathological and Clinical Physiology

  2. CHAPTERS • hearing • vestibular apparatus • taste • smell

  3. HEARING • regular compression vawes • transmitted in air(300m/s), water(1500m/s), and in a solid • type of mechanical disturbances based communication (head vibration in snakes, lateral line in fish) • external, middle, inner ear

  4. terminology TONES AND BACKGROUND NOISE • pitch tone: sine curve • pitch of a tone: frequency • volume (loudness): amplitude • harmonic vibration : tone quality (timbre of sound) • noise: non-periodic

  5. terminology

  6. terminology DECIBEL • sound intensitySound Pressure Level • range of hearing 20 microPa – 20 Pa – therefore decibel introduction • logarithmic unit SPL [dB] = 20 . log(px / po) where px is a measured value of acoustic pressure and po standard sound pressure 2.10-5 Pa

  7. terminology PHON subjective sound level depends on the frequency low frequency tone (60Hz) of the given sound pressure (90dB) is percieved like the reference tone having 80dB – 80 phons

  8. LOUDNESS OF COMMON SOUNDS

  9. EXTERNAL EAR • pinna (earlobe) and ear canal • act like a funnel and resonance chamber • localization of a source • amplification of the waves of specific f • in animals – mobile pinna MIDDLE EAR • cavity in temporal bone, Eustachian canal • ear drum, auditory ossicles, foramen ovale • lever arm system: magnification of the sound pressure 30x • tympanic reflex: contraction ofm. tensor tympani andm. stapedius, stapes out, defense function, 0.1 s

  10. INNER EAR • bony labyrinth (os temporale), membranous labyrinth • cochlea: 35mm, 2 ¾ turns, divided by basilar and Reissner’s membraneinto 3 chambers: the upperscala vestibuli andlowerscala tympani(helicotrema, perilymph, foramen ovale, foramen rotundum); the middlescala media (endolymph, does not communicate)

  11. ORGAN OF CORTI • outer hair cells: 3 rows, 20000 • inner HCs: 1 row, 3500 = receptor • membrana tectorialis - tips of outer hair cells are embedded

  12. tonotopical organization of the cochlea

  13. AUDITORY PATHWAY • innerhair cells • ganglion spirale • ncl. cochlearis doraslis et ventralis in oblongata • olivary nuclei ipsi + contra • (nc. lateral lemnicsi) • colliculi inferiores (auditory reflexes) • corpus geniculatum mediale (thalamus) • primary auditory cortex(temporal, Brodmann 41)

  14. BAEP The thalamus (medial geniculate ganglion) and the auditory cortex (temporal lobe) make up the middle and late waves of the AEP. auditory nerve = wave I cochlear nuclei = wave II superior olive = wave III lateral lemniscus = wave IV inferior colliculus = wave V Waves I-V make up the brainstem AEP.

  15. BRAIN AREAS • frequency of APsis proportional to the loudness • tonotopical character through whole pathway (cohlea to cortex)

  16. LOCALIZATION OF THE SOURCE • timing – difference in latency between both ears (20 ms is enough), important for the tones under 3000 Hz • difference in loudness between both ears, over 3000 Hz

  17. VESTIBULAR APPARATUS • located in os temporale, formed by membranous labyrinth • 3 semicircular canals and 2 cavities (saculle and utricle)

  18. SACCULE AND UTRICLE • sensory organ macula, in utricle horizontally, in saccule ventrically • macula contains hair cells, gelatinouslayer with CaCO3crystals • genesis of AP • linear acceleration, gravitation

  19. SEMICIRCULAR CANALS • each widen at the end to form ampula • ampulacontains cupula: analogous with macula (hair cells, excitated by the movements of endolymph) • angular acceleration

  20. Hair cells Vestibular nerve (Ganglion vestibularis) Ncc. vestibulares Vestibular ncc. efferents • Vestibuloocular III, IV, VI (oculomotor, trochlearis,abducens) • vestibulospinalis • Vestibulocerebellaris • VB complex – Sylvian fissure

  21. TASTE • Chemoreceptors • distant chemical sense • functions: • recognition of food, differentiation from poisons • strong coupling with behavior and emotions • the same for smell

  22. TYPES OF RECEPTORS • 13 types of taste receptors: • 2 receptorssodium, 2 kallium, 1 chlorine, 1 adenosin, 1 inosin, 2 saccharids, 2 bitter taste, 1 glutamate and 1 for H+ • beside them tactile and nociceptive receptors in mouth (V nerve)

  23. TASTE QUALITY • hundreds of tastes, maybe a result of combination of 4 basic (analogywith color vision) • sour taste • salt • sweet (sugar, glykol, ethanol, aldehyde, ketone, amide, AA, peptides) • bitter (long chained substances containing nitrogeon, alkaloid- chinin, kofein, strychnin, nicotine) • umami

  24. THRESHOLD VALUES • the lowest for the bitter taste (10-5 mol), the highest for salt and sweet (10-2 mol) • taste blindness fenylthiokarbamid (cabbage, broccoli): 30%

  25. RATIO • sweet: sucrose 1, 1-propoxy-2-amino-4-nitrobenzen 5000, fructose 1.7, glucose 0.8, lactose 0,3 • salt: NaCl 1, NaF 2, CaCl2 1, NH4Cl 2.5, KCl 0.6 • sour: HCl 1, formic a. 1.1, butiric a. 0.85, citric a. 0.46 • bitter: chinin 1, strychnin 3.1, cofein 0.4, morphine 0.02

  26. TASTE BUDS • 50 epithelial cells (taste and supporting cells) • taste pores, microvilli contains receptors, synapse nerves

  27. LOCALIZATION OF TASTE BUDS

  28. TASTE PATHWAYS • Buds • Facial nerve – Chorda tympani (ncc.) • Glossopharyngeal nerve (ncc.) • (vagus) • Tractus solitarius (gustatory ncc.) ----------- • Thalamus (VB complex) • Sylvian fissure (SSA1)

  29. SMELL • low known sense: • subjective, cannot be studied in animals • not well developed in humans (?)

  30. each nostril, surface area 2.4 cm2

  31. OLFACTORY CELLS • bipolar neurons, 100 millions • olfactory hairs, contain receptors • thousands of receptors, smell blindness • Bowman’s glands: secretion of mucus • ligand has to be water soluble • G-protein coupled receptors (amplification: 1 ligand => several G-protein => more adenylcyclases => lot of cAMP) • absolute and recognition thresholds (garlic

  32. ADAPTATION • during first few seconds 50% • then slow and weak • important role of CNS (similar to taste)

  33. OLFACTORY PATHWAYS • axons of olfactory cells throughlaminacribriformisto the bulbus olfactorius • synapse to the mitral cells (in glomerulus – segregation) • their axons viaolfactory tractto the olfactory cortex (ncl. olf. ant., pyriform cortex, tuberculum olfactorium, amygdala, entorhinal cortex)andreticular formation (arousal)

  34. OLFACTORY CORTEX • ncl. olf. ant.: coordination of contralateral inputs • pyriform cortex: smell discrimination • amygdala: emotion • entorhinal cortex: memory processes • eliciting salivary and gastric secretion • hygiene monitor • social information • sexual behavior

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