Neuro Block 2 - Ch. 10
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39 terms
Terms | Definitions |
|---|---|
 olfactory sensory neurons are located in | olfactory epithelium at top of nasal vault along upper portion of nasal septum & cribriform plate region |
| permanent loss of olfaction can result from | 1. accidental whiplash if cribriform plate is fractured 2. hemorrhage at base of frontal lobe that may tear the olfactory filaments >but typically location deep in nose protects it |
| olfactory mucosa | several layered epi consisting of 1. olfactory sensory neurons >~40d ; ~ 100million; bipolar w/cilia extending from apex to mucus; base =unmyelinated axon > hundreds are bundled together by Schwann sheath > 1' olfactory nerve bundle =all axons of all sensory neurons > passes thru cribriform plate > olfactory bulb 2. supporting cells 3. basal cells > stem cells, replacement and reinnervate olfactory bulb |
| olfactory transduction occurs in | cilia of olfactory sensory neurons |
| odorant molecules bind to | odorant receptors located in ciliary membrane & olfactory knob of olfactory sensory neurons |
| how does the olfactory system discriminate btw large numbers of odorant molecues | ~300-400 odorant genes ~several thousand odors >olfactory epi is divided into 4 spatially distinct zones of gene expression >neurons expressing the same odorant receptor > one distinct zone > to the same glomerulus in olfactory bulb >>olfactory bulb is topographically organized w/ individual glomeruli representing a single type of odorant receptor + >one odorant activates several types of receptors >every receptor may be activated by several different odorants BUT one odorant activates A UNIQUE COMBO of receptors >a family of odorant receptors is used in COMBO to allow the olfactory system to recognize many different odorants |
| how is binding of an odorant molecule to receptors converted into an electrical signal? | >transducers convert chemical into electrical >involves olfactory cilia and knob @ apical region of sensory neuron 1. binding of odorant to receptor in cilia > G protein activation of adenylate cyclase > increase in cAMP > opens ionic channels in plasma membrane 2. inward graded generator potential (Na & Ca) >>depol 3. generator potential > spreads passively to dendrites & cell body of olfactory sensory neuron > trigers AP > conducted along axon > to olfactory bulb |
| generator potential is graded as a function of __ and modulates __ | stimulus intensity mod. freq of AP discharge in olfactory receptor cell axon |
| graded potential produced by odorants is called | generator potential 1st neuron is olfactory sensory cell that supports spike generation |
| in auditory and taste > graded potential is called | receptor potential bc receptor modulates impulse discharge 1st neuron is 1' afferent that supports spike generation |
| laminar organization of olfactory bulb | 1. axons of olfactory receptors enter olfactory bulb > converge to form glomeruli; terminate @ glomeruli w/ great convergence (25,000axons synapse w/~25mitral cells) 2. mitral cell axons > proceed to depth of bulb > project posteriorly to emerge together to from the lateral olfactory tract 3. periglomerular cells form a reciprocal synapse w/ mitral cell dendrites > inhibiting mitral cells in surrounding glomeruli >> lateral inhibition |
| mitral cell | 2nd order neuron in olfactory sytem main output neuron of olfactory bulb |
| periglomerular cells | intrinsic inhibitory interneurons surrounding the glomeruli |
| primary olfactory cortex consists of | piriform cortex, including: 1. lateral olfactory gyrus 2. cortical regions of uncus (aka periamygdaloid cortex) |
| some olfactory fibers project direclty to the | corticomedial part of amygdala |
| the olfactory association cortex is the | anterior part of the parahippocampal gyrus >but this cortical area also receives a few direct projections from the olfactory tract |
| the olfactory system is the only sensory system that does not have a | thalamic relay b4 projecting to 1' sensory cortex |
| taste buds | 1. receptor organ for taste 2. widely distributed thru out the oral cavity; most concentrated on the tongue 3. assoc w/ specialized papillae 4. collection of 40-50 cells 5. microvilli extend from the apices and are in direct contact w/ saliva (taste molecules interact w/ the microvilli) 6. ea taste nerve fiber divides many times b4 approaching the base 7. A single fiber of chorda tympani may innervate multiple taste buds and many cells w/ in ea taste bud >>electrical activity from one fiber = activity from many taste cells 8. basal cells (surrounding taste buds) continually replace taste cells q 10d 9. the taste bud is maintained, the cells w/in it in constant flux 10. so taste nerve endings are also continuously moving and innervating new taste cells! |
| papillae | folds in skin of tongue 1. fungiform - 100 > ant. 2/3 of dorsal tongue surface >ea consists of 1-5 taste buds innervated by chorda tympani (CN 7) > readily exposed, respond quickly > sensitive to sweet and salty 2. foliate - on each side of the tongue near post region >innervated by branches of CN 7 and ( 3. circumvallate - post tongue > taste buds in trenches that surround ea papilla >innervated by CN 9 > substances must diffuse into these trenches b4 stimulating the taste buds >very sensitive to bitter |
| taste buds in palate innervated by | CN 7 |
| taste buds in epiglottis innervated by | CN 10 |
| some taste chemical stimuli produce activity in the __ system thru stimulation of nerve ending in the nasal and oral cavities | trigeminal system (CN5) > carry info regarding chemical irritation |
| umami | >delicious taste; amino acids; monosodium glutamate T1R2, T1R3 coupled to G-protein > PLC > IP3 > opening of TRPM5 channels > Ca influx > depolarize taste cell |
| salty | >Na+ in NaCL Na channel receptor potential generated by inward Na current > depolarizes the taste cells > inital depol activates voltage -dep -Na channels > AP > influx of Ca++ > neurotransmitter release |
| sour | > H+ in acids ; HCl H+ sensitive cation-selective channel receptor potential generated by inward H+ current > depolarizes the taste cells > inital depol activates voltage -dep -Na channels > AP > influx of Ca++ > neurotransmitter release |
| sweet | >sucrose T1R2, T1R3 coupled to G-protein > PLC > IP3 > opening of TRPM5 channels > Ca influx > depolarize taste cell |
| bitter | T2R coupled to G protein > PLC > IP3 > opening of TRPM5 channels > Ca influx > depolarize taste cell |
| fibers from __ papillae run predominantly in the LINGUAL - TONSILLAR branch of glossopharyngeal nerve | vallate & foliate |
| fibers from __ papillae run in ANT. 2/3 of tongue enter CHORDA TYMPANI branch CN7 | fungiform |
| cell bodies of cells w/ axons in chorda tympani are located in __ AND synapse in __ | the geniculate ganglion of facial nerve 7 synapse in medulla in ispilateral rostral nucleus tractus solitarius* |
| cell bodies of cells w/axons in glossopharyngeal nerve are in ___ and terminate on | petrosal ganglion term on diff neurons and in some overlapping areas in the rostral nucleus tractus solitarius* |
| taste buds on the epiglottis and esophagus are innervated by the | internal portion of the superior laryngeal nerve (branch of vagus CN10) |
| peripheral nerves w/ diff degrees of responsiveness to >sucrose, NaCl, HCl, or quinine project to | the nucleus of the solitary tract |
| the fibers of nerves 7,9,10 project to | an organizes, overlapping termination w/in rostral nucleus tractus solitarius |
| 2nd order (taste) cells project to __ which send projections to __ >lower vs higher mammals | the parabranchial nuclei in the pons > project to lateral hypothalamus & amygdala LOWER mammanls >parabranchial nuclei > MEDIAL LEMNISCUS> VPM >insular cortex HIGHER mammals rostral nucleus tractus solitarus > 1 or 2 1. CENTRAL TEGMENTAL TRACT >medial part of VPM > gustatory cortex = parietal operculum or opercular-insular cortex 2. parabranchial nucleus in rostral pons >lateral hypothalamus && central nucleus of amygdala |
| parabranchial nucleus | in rostral pons (near sup. cerebellar peduncle) |
| gustatory cortex | 1. parietal operculum = post-central gyrus (near representation of tongue) 2. opercular-insular cortex (overlying claustrum) |
| area postrema | located rostral to obex on each side of 4th ventricle >major afferent input = from nucleus tractus solitarus >lies outside the blood-brain barrier = circumventricular organ |
| stimulation of emetic chemotaxic center in the ___ triggers vomiting | area postrema |
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