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PREPARATI ONOFASAMPLE UNI TOFTEXTUALMATERI AL
By Ar at hi . S. Nai r Nat ur al Sci ence
BI OLOGY
STANDARD–X
CONTENT Sensoryrecept i onand pr ocessi ng. 9
7-
St r uct ur eofey e
10-
Thechemi st r yofv i si on
15-
14 25
St r uct ur eandf unct i onofear 2633
Todet ectt ast e. 36
34-
Todet ectsmel l .
37-
Recept or si nt heski n.
40-
39 42
1.SENSORY RECEPTI ONAND PROCESSI NG Hav ey ouev ert houghthowdoy ou f eel t hecl i mat i cchangesi nt he env i r onment ?Howdoy ouseean
obj ectandi t ’ scol our ?Howdoy ou hearasound? Thesensor yor gansdet ectal l t y pesofchangesi nt heenv i r onment andsendappr opr i at esi gnal st ot he CNSwher eal l t hei nput sar e pr ocessedandanal y sed.Si gnal sar e t hensentt odi f f er entpar t s/cent r es oft hebr ai n.Thi si showy oucan sensechangesi nt heenv i r onment .
Sensor yor gans Wesmel l t hi ngsbyournose, t ast eby t ongue, hearbyearandseeobj ect s
byey es. Thenosecont ai nsmucus coat edr ecept or swhi char e speci al i zedf orr ecei v i ngt hesenseof smel l andcal l edol f act or yr ecept or s. Expandt hegi v ent abl ebyaddi ng senseor gansandt hei rr ecept or s.
Tabl e: 1. 1senseor gansandr ecept or s LetusAssess Whatar esenseor gans? Whyar esenseor gansi mpor t ant ?
EXTENDEDACTI VI TY Col l ectmor ei nf or mat i onabout senseor gansi nhumanbei ngs.
2.STRUCTUREOFEYE Ey ei st hesenseor gant hathel pst he br ai nt oev okesensat i on. Howar et he ey espr ot ect ed?Di scussandf i l l i nt he bl anks.
Howf ari st hest r uct ur eofaney e adapt edt oper f or mi t ’ sf unct i on?Obser v e t hef i gur eandi l l ust r at i on, wr i t ey our
i nf er encesi nt hesci encedi ar y . Fi g. 2. 1:St r uct ur eoft heey e.
I l l ust r at i on2. 1: t heey epar t sandf unct i on.
LetusAssess Whatar et hel ay er soft heey eandt hei r f unct i ons? Whati spupi l andwher ei ti sl ocat ed? Whati st hef unct i onoft heaqueous humor ? Howt heposi t i onandsi gni f i canceof
l enseandcor neahel pt heent r yofl i ght ? EXTENDEDACTI VI TY Pr epar ea3Dmodel ofey eusi ngt he mat er i al sav ai l abl ei ny ourl ocal i t y .
3.THECHEMI STRYOF VI SI ON Ret i naandt hephot or ecept or s Youmi ghthav eunder st oodt hat phot or ecept or sar epr esenti nt her et i na. Rodcel l sandconecel l sar et he phot or ecept or si nt her et i na. Rodcel l sar e mor ei nnumbert hanconecel l s. Obser v ef i gur e3. 1andr el at et heshapeof phot or ecept or swi t ht hei rnames. Anal y se t hedescr i pt i onandcompar et he phot or ecept or sandcompl et et abl e3. 1.
Fi g: 3. 1
Rodcel l scont ai nt hev i sual pi gmentcal l ed
r hodopsi n. Thi spi gmenti sf or medf r om a pr ot ei nnamedopsi nandr et i nal whi chi sa der i v at i v eofv i t ami nA.Si ncet heyar e act i v at edev eni ndi ml i ght , wear eabl et o seeobj ect si ndi ml i ght .Thesecel l scannot det ectcol our . Conecel l scont ai napi gmentcal l ed phot opsi n.Thi si sal socal l edi odopsi n. Thi spi gmenti sal socomposedofopsi n andr et i nal .Ther ear et hr eet y pesofcone cel l si nourey es, whi chhel pust odet ect t hr eepr i mar ycol our sofl i ght r ed, gr eenand
bl ue. Thi sdi v er si t yi sduet ot hedi f f er ence i nami noaci dsi nt heopsi n mol ecul e. So, conecel l spr ov i deuswi t h col ourv i si on. Thechemi st r yofv i si on Howar ei mpul sesf or medi n phot or ecept or st omakev i si onpossi bl e? Anal y set hei l l ust r at i on3. 1andf i gur e3. 2 andt hedescr i pt i onandwr i t ey our i nf er encesi nt heSci encedi ar y .
I l l ust r at i on3. 1
Fi g: 3. 2: senseofsi ght I nt hepr esenceofl i ght , t hepi gment s pr esenti nphot or ecept or s, di ssoci at e.Thi s chemi cal changel eadst ot hef or mat i onof i mpul ses.Thesei mpul sesar et r ansmi t t ed t ot hecer ebr um t hr oughopt i cner v esand t hi senabl esv i si on.
Ey e-def ect sanddi seases Youar enowawar eofsomeoft heey e def ect s.Pr epar eanot eoney edef ect sand t hei rr emedi es. Letusf ami l i ar i seour sel v eswi t haf ew mor eey edef ect sanddi seases. Col ourBl i ndness Obser v ef i gur e3.3
Fi g3. 3 Cany our eadt hef i gur ecl ear l y ? Youar eawar et hatt her et i nacont ai ns conecel l swhi chcandet ectr ed, gr een andbl uecol our s.Someper sonscannot di st i ngui shgr eenandr edcol our sduet o t hedef ectofconecel l s.Thi scondi t i on i scal l edcol ourbl i ndness. Cany ouguesswhyper sonawi t hcol our bl i ndnessar enotsel ect edf ormi l i t ar yor f orj obsl i ket hatofapi l ot , dr i v eret c? Di scuss. Ni ghtbl i ndness Youhav est udi edt hatt her et i nal , apar tof t hev i sual pi gment, i sder i v edf r om v i t ami n A.Thedef i ci encyofv i t ami nAr esul t si nt he l owpr oduct i onofr et i nal .Thi si nt ur n
pr ev ent st her esy nt hesi sofr hodopsi n. I n t hi scondi t i onobj ect scannotbeseen cl ear l yi ndi ml i ghtandt hi spdi seasei s cal l edni ghtbl i ndness. Xer opht hal mi a I ft her ei sapr ol ongeddef i ci encyof v i t ami nAt heconj unct i v aandcor nea becomedr yandopaque. Thi scauses xer opht hal mi aandl eadsul t i mat el yt o bl i ndness. Gl aucoma Aqueoushumori st hef l ui dwhi ch nour i shest het i ssuesi nt heey es. I ft he r eabsor pt i onof aqueoushumordoesnotoccur , i t causesani ncr easei nt hepr essur e i nsi det heey es. Thi scausesdamaget o t her et i naandt hephot or ecept orcel l s
andul t i mat el yl eadst obl i ndness. Thi s def ecti scal l edgl aucoma.I tcanbe r ect i f i edbyl asersur ger y . Cat ar act I ti sacondi t i oni nwhi cht hel ensoft he ey esbecomeopaquer esul t i ngi n bl i ndness. Thi scanber ect i f i edby r epl aci ngt hel enswi t hanar t i f i ci al one t hr oughsur ger y . Pr ot ect i onofEy es. Whatar et het hi ngst obet akencar eof t oensur et heheal t hoft heey es? Di scussont hebasi soft hei ndi cat or s gi v enbel ow. I ndi cat or s Foodmat er i al sr i chi nv i t ami nAand heal t hoft heey e
Excessi v euseofmobi l e, comput eret c andheal t hoft heey e. Ey eDonat i on
I nI ndi awehav eanest i mat ed4. 6mi l l i on peopl ewi t hcor neal bl i ndnesst hati s cur abl et hr oughcor neal t r anspl ant at i on madepossi bl ebyey edonat i on.The cor neai st hecl earsur f aceatt hef r ont oft heey eandi st hemai nf ocussi ng
el ement . Whent hecor neabecomes cl oudyf r om di sease, i nj ur y , i nf ect i onor anyot hercause, v i si onwi l l bedr ast i cal l y r educed. Coneat r anspl anti st hesur gi cal pr ocedur ewhi chr epl acesadi scshapedsegmentofani mpai r edcor nea wi t hasi mi l ar l yshapedpi eceofa heal t hydonorcor nea. Mor et han90%oft hecor neal t r anspl ant at i oni scar r i edout successf ul l yandhel psr est or ev i si oni n peopl ewi t hcor neal bl i ndness. LetusAssess Whatar et hef act or spr esenti nv i sual pi gment s? Howar ei mpul sesf or medi n phot or ecept or st omakev i si on
possi bl e? Pr epar eanot eoney edef ect sand t hei rr emedi es. Pr epar eapost err egar di ngey e donat i on EXTENDEDACTI VI TI ES Conductasemi nari ncl assont he t opi c” Ey edi seasesandpr ot ect i onof t heey e”.
4. STRUCTUREAND FUNCTI ONOFEAR Youhav est udi edt hataudi t or yr ecept or s ar epr esenti nt heear . Theearnotonl y hel psusi nhear i ng, butal soi n mai nt ai ni ngt hebal anceoft he
body . Obser v et hef i gur e4. 1andl i stt he
mai npar t soft heear . Fi g. 4. 1: St r uct ur eofear Letusexami net hemai npar t soft heeari n det ai l . Ex t er nal ear
I ndi cat or s Funct i onofpi nna I mpor t anceoft heaudi t or ycanal Mi ddl eear Anal y sef i gur e4. 2andpr epar eat abl e byi ncl udi ngt hepar t soft hemi ddl eear andt hei rf unct i on.
Fi g. 4. 2: St r uct ur eoft hemi ddl eear .
I nt er nal ear Obser v et hef i gur e4. 3andunder st and t hepar t soft hei nt er nal ear .
Fi g. 4. 3: st r uct ur eofi nt er nal ear
Howi shear i ngpossi bl e?
Cochl eai sacoi l edt ubel i keasnai l shel l . I tconsi st soft hr ee chamber s. Speci al i sedsensor yhai rcel l s whi char epr esenti nt hebasi l ar membr anet hatsepar at est hemi ddl e andl owerchamber s, f unct i onas audi t or yr ecept or s. Thebasi l ar membr aneandsensor yhai rcel l s t oget herconst i t ut et heOr ganofCor t i .
Thesoundwav eswhi chpasst hr ough t heext er nal earv i br at et he t y mpanum. Thi sv i br at i onoft he t y mpanum i st r ansmi t t edt ot heear ossi cl eswhi chcausest hev i br at i onof t hemembr anei nt heov al wi ndow. Thi s v i br at i onf ur t hercausest hemov ement oft hef l ui di nsi det hecochl ea. Asa r esul t , t hesensor yhai rcel l soft he Or ganofCor t i oft hecochl eaar e st i mul at edandi mpul sesar e gener at ed. Thesei mpul sesr eacht he cer ebr um t hr ought heaudi t or yner v e andhear i ngi sef f ect ed. EarandBodybal anci ng Doesn’ tt heearhel pi nmai nt ai ni ngt he bal anceoft hebody ?Howi si tpossi bl e?
Anal y set hef i gur eanddescr i pt i on.
LetusAssess Whatar et hemai npar t sofhumanear ? Whatar et hef unct i onsofhumanear ? Howdoest heearmai nt ai nsbal ance? Howi shear i ngpossi bl e? EXTENDEDACTI VI TY
Col l ecti nf or mat i onr egar di nghear i ngai ds
5. TODETECTTASTE I sn’ tt ast e, oneoft her easonsf orenj oy i ng t hef oodweeat ?Whatar et hedi f f er ent t y pesoft ast eswecandet ect ?
Recept or si nt het ongue
Chemor ecept or sseeni nsi det hemout h andt onguehel pust odet ectt ast e. These ar eseenmai nl yont hesur f aceoft he t ongue. Thepr oj ect edst r uct ur esseenon t hesur f aceoft het onguear ecal l ed papi l l ae. Thepar t sseenont hepapi l l aet hat det ectt ast ear et het ast ebuds. Wehav e t ast ebudst hatar est i mul at edbyt ast es l i kesweet , sal t , sour , bi t t er , umami et c.
Eacht ast ebudhaschemor ecept or st hat hel pt odet ectdi f f er entt ast es. Subst ances r esponsi bl ef ort ast edi ssol v ei n sal i v a, st i mul at et hechemor ecept or sand gener at ei mpul ses. Thesei mpul sesr each t hebr ai nt hr ought her espect i v ener v esand
weexper i encet ast e. LetusAssess Whatar et ast ebuds? Howdoesoursenseoft ast ewor k? EXTENDEDACTI VI TY Col l ectmor ei nf or mat i onaboutt he di v er si t yoft ast es.
6. TODETECTSMELL Howdowedet ectsmel l ?Wehav e
di scussedol f act or yr ecept or s. Anal y se Fi gur e6. 1andcompl et et hest agesi n t hepr ocessofdet ect i ngsmel l .
Fi g. 6. 1: ol f act or yr ecept or s St ages Ar omat i cpar t i cl esdi f f usei nt heai rand ent ert henost r i l s.
Thesear omat i cpar t i cl esdi ssol v ei nt he mucusi nsi det henost r i l s. I sn’ tt her eapossi bi l i t yofnotsensi ng t het ast eoff oodwhi l esuf f er i ngf r om commoncol d?Di scuss.
LetusAssess
Howdowesmel l ? Whatar et hest agesi nt hepr ocessof det ect i ngsmel l ? EXTENDEDACTI VI TY Pr epar eaf l owchar tshowi ngdi f f er ent st agesofsensi ngsmel l .
7. RECEPTORSI NTHE SKI N Youmi ghthav eseenv i sual l yi mpai r ed peopl er eadi ngBr ai l l ebyt ouchi ngwi t h t het i psoff i nger s. Ar et heset ouch r ecept or suni f or ml ydi st r i but edal l ov er t heski n?
Obser v ef i gur e7. 1andunder st andt he v ar i ousr ecept or spr esenti nt heski nt o senset hedi f f er entst i mul i i .
LetusAssess Whi chsensor yr ecept or sar epr esenti n i nt heski n? EXTENDEDACTI VI TY
Pr epar enot esont hepecul i ar i t i esofsense or gansofdi f f er entor gani smsbycol l ect i ng mor ei nf or mat i on.