Control and Coordination: Class 10 Science Chapter 6 Hinglish mein

Tum bus mein ghar jaate hue padh rahe ho, tabhi ek machchhar tumhari kalaai par baith jaata hai. Tumhe chubhan mehsoos hoti hai, tumhara doosra haath use maar deta hai, aur tumhari aankhein page se hatti tak nahi. Thodi der baad driver zor se brake lagata hai, aur bina soche tum aage wali seat pakad lete ho. Kuch hi seconds mein tumhare body ne aas-paas ke do changes notice kiye aur har ek ka jawab bilkul sahi movement se diya.

Jis change ko koi living thing detect kar sake, use stimulus (उद्दीपन; plural stimuli) kehte hain, aur us change par woh jo karta hai woh uska response hai. Response stimulus ke hisaab se hona chahiye. Chehre ki taraf tez aati cricket ball se tum jhuk kar bachte ho, lekin aaram se uchhaali gayi ball ko pakadne ke liye haath badhaate ho. Sahi response chunna control hai. Aankhon, brain, haathon aur pairon ko saath mein, sahi order mein kaam karwana coordination hai.

Movement woh response hai jo hum sabse zyada notice karte hain. Kuch movements sirf growth se aati hain: kuch dinon mein windowsill par rakha sunflower ka seedling glass ki taraf jhuk jaata hai, aur lauki ki bel fence ke taar par lipat kar upar chadh jaati hai. Kuch ka growth se koi lena-dena nahi: keede par jhapatti chhipkali, poonchh hilata kutta, tumhari apni palkein jhapakna. Dono tarah ki movements control hoti hain. Bahut saare cells se bane body mein yeh kaam special tissues karte hain. Yeh chapter pehle un do systems ko dekhta hai jo animals use karte hain, nerves aur hormones, aur phir yeh ki plants bina kisi nerve ke yeh kaam kaise kar lete hain.

6.1 Animals mein Nervous System

Har response ek change ko notice karne se shuru hota hai. Animals mein notice karna, messages le jaana aur decide karna nervous tissue karta hai, aur aakhri action muscle tissue karta hai; dono se tum Class 9 mein mil chuke ho.

Detect karna receptors (ग्राही) ka kaam hai: aisi nerve cells jinki tips ek tarah ke change par respond karne ke liye bani hoti hain. Aankh ke receptors light par respond karte hain, naak ke olfactory receptors smell par aur jeebh ke gustatory receptors taste par (Table 6.1). Zyadatar receptors sense organs mein group mein hote hain, lekin skin mein yeh poore mein faile hote hain.

Nervous tissue ki basic unit nerve cell, yaani neuron (तंत्रिका कोशिका) hai. Fig. 6.1 mein iske parts dekho:

• Dendrites: cell body ke aas-paas chhote, shaakhaon wale dhaage. Inki tips information pakadti hain, ya to kisi stimulus se ya kisi doosre neuron se.
• Cell body: sabse chauda hissa, jismein nucleus hota hai aur jo cell ko zinda rakhta hai.
• Axon: ek lamba fibre jo signal ko cell body se door le jaata hai. Tumhare pair mein neeche tak jaane wala ek akela axon lagbhag ek metre lamba ho sakta hai.
• Nerve endings: axon ka shaakhaon wala sira, jahan message agle cell ko diya jaata hai.

Safar mein message ka roop badalta hai: neuron ke andar woh electrical hota hai, lekin do neurons ke beech chemical. Ek message ko Fig. 6.1 aur Fig. 6.2 mein follow karo:

1. Jab dendrite ki tip stimulate hoti hai, to wahan ke chemical changes stimulus ko ek chhote electrical signal, yaani electrical impulse, mein badal dete hain.
2. Jaise rassi par ek lehar chalti hai, waise hi impulse aage badhta hai, cell body se hokar axon ke aakhir tak.
3. Paas-paas ke neurons kabhi poori tarah ek doosre ko chhoote nahi. Jab impulse nerve endings tak pahunchta hai, to cell do cells ke beech ke patle gap mein thode se chemicals chhodta hai. Yeh gap synapse hai.
4. Doosri taraf, chemicals agle neuron ke dendrite se jud jaate hain. Isse ek bilkul naya electrical impulse shuru hota hai, aur relay aage chalta rehta hai. Yeh poora crossing ek second ke hazaarven hisse se bhi kaafi kam samay leta hai.
5. Chain ke aakhir mein, isi tarah ka junction message ko ek muscle cell ya gland cell ko deta hai, jo phir action leta hai.

6.1.1 Reflex Actions mein kya hota hai?

Ghaas par nange pair chalo aur kaanta chubh jaaye: 'ouch' bolne se pehle hi tumhara pair jhatke se upar uth jaata hai. Dhool ka ek kan aankh ki taraf aata hai aur tum palak jhapka dete ho. Doctor ghutne ki katori ke theek neeche halke se maarta hai aur tumhara pair apne aap aage ki taraf uchhal jaata hai. Har ek reflex action (प्रतिवर्ती क्रिया) hai: stimulus par ek tez, automatic response, jo bina soche hota hai.

Brain ko hi decide kyun na karne dein? Kyunki decide karne mein time lagta hai. Ek thought ek signal nahi, balki signals ka toofan hai, jo bahut saare neurons ke beech idhar-udhar ghoomta hai. Kaante ke case mein, pain signal ko pehle ek metre se zyada lambi nerve se sir tak chadhna padta. Brain usse tolta, aur phir ek command ko poora raasta wapas pair tak aana padta. Tab tak kaanta andar ghusta hi rehta.

Body ka jawab ek short cut hai. Spinal cord ke andar aane wali 'pain' nerve lagbhag seedhe us jaane wali nerve se judi hoti hai jo pair ki muscles chalati hai, isliye command wahin de diya jaata hai, brain ka intezaar kiye bina. Spinal cord is kaam ke liye theek hai kyunki dhad aur haath-pairon ki har nerve waise bhi usi se hokar guzarti hai. Stimulus se response tak ke is sabse chhote raaste ko reflex arc (प्रतिवर्ती चाप, Fig. 6.3) kehte hain. Yeh school gate ke us guard jaisa hai jise pehle se orders mile hain: aag lag jaaye to woh turant gate khol deta hai aur principal ko baad mein batata hai.

Brain ko chhoda nahi jaata. Receptor se aaya message spinal cord se upar bhi jaata hai, isliye pair jhatke se hatne ke ek pal baad tumhe dard mehsoos hota hai aur pata chalta hai ki kya hua.

Life ki history mein tez, wired responses pehle aaye. Jellyfish mein nerves ka sirf ek dheela jaal hota hai aur brain bilkul nahi, phir bhi chhoote hi woh apne tentacles andar kheench leti hai. Bade, sochne wale brains bahut baad mein aaye, aur jin animals mein yeh hain unhone apne reflex arcs bhi rakhe, kyunki emergency mein isse tez kuch nahi.

6.1.2 Human Brain

Brain aur spinal cord milkar central nervous system (CNS) banate hain, jo body ka control room hai. Har organ se reports wahan aati hain, aur CNS respond karne se pehle unhe jodta hai. Brain main coordinating centre hai. Spinal cord reflexes chalaane ke alawa woh highway bhi hai jo messages ko upar brain tak aur commands ko wapas neeche le jaata hai.

Din bhar tum jo karte ho, uska zyadatar hissa reflex nahi hota. Football ko kick karna, glass mein paani daalna ya pankha chalana voluntary actions hain: inhe karne ka decision tum lete ho. To muscles do raaston se orders leti hain: reflex mein seedhe spinal cord se, ya decision lene par brain se.

Nerves CNS ko baaki body se jodti hain. Brain se baarah jode cranial nerves nikalte hain, aur spinal cord se ikattees jode spinal nerves. Dono milkar peripheral nervous system (PNS) banate hain, yaani CNS aur sense organs, muscles aur glands ke beech cables ka network.

Brain ke alag-alag parts alag-alag kaam karte hain. Brain ke teen main regions hain: fore-brain, mid-brain aur hind-brain (Fig. 6.4).

Fore-brain sochne wala part hai; iska sabse bada hissa cerebrum hai. Ise kaam karte dekho. Tumhe kuch meetha talne ki khushboo aati hai, chhan-chhan ki awaaz sunaai deti hai aur kadhai mein sunehri jalebi jaise golay dikhte hain. Har sense apne impulses cerebrum ke apne sensory area tak pahunchata hai: ek area dekhna sambhalta hai, doosra sunna, teesra smell, aur aise hi. Phir association areas teeno reports ko jodte hain aur memory se match karte hain: jalebis! Sab samajhne ke baad fore-brain tay karta hai ki kya karna hai, aur uske motor areas voluntary muscles ko orders bhejte hain jo tumhara haath plate ki taraf badhaati hain.

Fore-brain jo kuch sense karta hai, woh sab aankh, kaan ya naak se nahi aata. Teesre paranthe ke baad ruk jaane wali feeling hypothalamus mein bhookh aur pet bharne ke ek centre se aati hai, jo fore-brain ke base par hai. Hypothalamus pyaas aur body temperature ko control karne mein bhi madad karta hai, aur jaisa tum Section 6.3 mein dekhoge, yeh kai hormones ke release ko direct karta hai.

Kuch actions chalte rehte hain, chahe hum unpar dhyaan dein ya nahi. Raat bhar tumhara heart dhadakta rehta hai, pet tumhare lunch ko mathta rehta hai, aur gehri neend mein bhi tum nigalte aur saans lete ho. Sirf decide karke inhe aasaani se shuru ya band nahi kiya ja sakta. Yeh involuntary actions hain, aur zyadatar ko mid-brain aur hind-brain chalaate hain.

Mid-brain aankhon aur sir ke tez, automatic adjustments karta hai, jaise pupils ka size badalna ya achanak dhamaake ki taraf sir ghumaana.

Hind-brain ke teen parts hain. Medulla involuntary actions control karta hai, jaise heartbeat, blood pressure, saliva ka behna, nigalna, khaansi, chheenk aur ulti. Pons brain regions ke beech messages relay karta hai aur saans ko regulate karne mein medulla ki madad karta hai. Cerebellum voluntary movements ko smooth aur precise banata hai aur body ka posture aur balance banaaye rakhta hai. Sui mein dhaaga daalna, saaf likhna, ek pair par balance karna aur chalti bus mein sthir khade rehna, sab isi par nirbhar hain.

6.1.3 In Tissues ki suraksha kaise hoti hai?

Brain tissue naram hota hai, jame hue dahi se zyada sakht nahi, aur aasaani se chot kha sakta hai. Yeh cranium mein rehta hai, jo skull ka gol hissa hai. Haddi aur brain ke beech protective membranes hoti hain jinke beech fluid bhara hota hai. Jab sir ko jhatka lagta hai, to fluid brain ke liye cushion ka kaam karta hai, bilkul waise jaise band jar mein paani tairte ande ko bachata hai. Spinal cord ka apna kavach hai. Gardan se neeche ki taraf apni peeth ke beech mein dabaao, to tum haddi ki alag-alag ubhri gaanthein gin sakte ho. Yeh vertebral column (backbone) ki hain: ring jaisi haddiyon ka dher jiske beech se spinal cord guzarta hai (Fig. 6.4 ka aakhri step).

6.1.4 Nervous Tissue Action kaise karwata hai?

Tumhari har movement, palak jhapakne se lekar daudne tak, muscle cells ke ek simple kaam par khatam hoti hai: chhota hona. Muscle dono siron par haddiyon se judi hoti hai, isliye jab uske cells chhote (contract) hote hain, to muscle haddiyon ko paas kheenchti hai aur tumhara haath mudta hai ya pair jhoolta hai. Nervous system ka kaam sahi muscles ko batana hai ki yeh kab karna hai.

Har muscle cell ke andar do tarah ke protein threads ke bundles hote hain, jo dheele se phansaaye do haathon ki ungliyon ki tarah overlap karte hain. Nerve ending aur muscle ke junction par pahuncha nerve impulse ek chemical change shuru karta hai. Proteins apni shape badalte hain aur threads ko ek doosre ke aur andar kheench lete hain, bilkul waise jaise phansi ungliyaan aur gehri sarakti hain. Threads ki length wahi rehti hai, lekin poora cell chhota ho jaata hai (Fig. 6.5).11Do main muscle proteins actin aur myosin hain. Inse tum Class 11 mein miloge.

6.2 Plants mein Coordination

Plants khatre se bhaag nahi sakte, na khaane tak chal kar ja sakte hain, aur unmein na nerves hain na muscles. Phir bhi woh bilkul sthir nahi hain. Tez chalaayi gayi films mein shoots sir hilaate, tendrils gol ghoomte aur leaves khulte-band hote dikhte hain. Chhui-mui (touch-me-not, Mimosa pudica) ki patti ko chhoo do to uske leaflets ek-do second mein band ho jaate hain; windowsill par rakha seedling glass ki taraf jhukne mein kai din leta hai. Yeh plant movement ki do tarah hain, jo neeche saath-saath rakhi gayi hain.

6.2.1 Stimulus par Turant Response

Chhui-mui ki patti ka mudna paani se chalta hai. Har leaflet ke base par, aur jahan leaf stalk stem se judta hai, cells ka ek chhota phoola hua cushion hota hai. Paani se bhare hone par yeh cells sakht hote hain, achhi hawa bhare tyre ki tarah, aur patti ko khula rakhte hain. Chhoone par inmein se kuch cells jaldi paani kho dete hain; woh dheele pad jaate hain, isliye leaflets band ho jaate hain aur stalk latak jaata hai (Fig. 6.6). Lagbhag aadhe ghante mein paani wapas aata hai, cells phir sakht hote hain aur patti khul jaati hai. To plant ki 'motor' cells ke andar ka water pressure hai, muscle ke protein threads nahi.

Ab sirf ek leaflet ki tip ko chhoo kar dekho. Mudna un leaflets tak bhi phail jaata hai jinhe tumne chhua hi nahi, to chhoone ki khabar zaroor aage gayi hogi. Plants aise signals ek cell se agle cell tak electrical aur chemical changes se bhejte hain. Lekin animals ki tarah inke paas is kaam ke liye koi special tissue nahi hai: aam cells hi message relay karte hain.

6.2.2 Growth se Movement

Karela (karela, bitter-gourd) ki bel apne aap khadi nahi ho sakti, isliye woh chadhti hai. Iske tendrils, pattiyon ke paas ke patle dhaage, dheere-dheere idhar-udhar hilte hain jab tak koi kisi cheez ko chhoo na le. Phir uneven growth kaam sambhalti hai: support ko chhoone wali side ke cells lagbhag lambe hona band kar dete hain, jabki bahar wali side ke cells badhte rehte hain. Jo dhaaga bahar wali side par tez badhe, use andar ki taraf mudna hi padega, isliye ek din ke andar tendril support ke chaaron taraf kas kar lipat jaata hai (Fig. 6.7).

Plants ke hisaab se tendrils tez hain. Zyadatar growth responses mein din lagte hain, aur hum unhe tabhi notice karte hain jab peeche mudkar dekhte hain ki plant ab kisi nayi taraf point kar raha hai. Jab light ya gravity jaisa koi stimulus tay karta hai ki plant ka koi part kis direction mein badhega, to woh response tropism (अनुवर्तन) hai. Stimulus ki taraf growth positive hai; usse door growth negative hai.

Light ke response mein growth phototropism hai. Shoots light ki taraf badhte hain (positive) aur roots usse door (negative). Windowsill par rakha money plant jaldi hi glass ki taraf jhuk jaata hai, aur andhere storeroom mein seedlings darwaaze ke neeche ki light ki patti ki taraf lambe ho jaate hain. Light ki taraf jhukne se leaves ko photosynthesis ke liye zyada dhoop milti hai, jabki usse door badhne se roots andhere soil mein rehti hain, jahan paani aur minerals hain.

Light akela signal nahi hai. Chane ka beej ulta bo do, phir bhi uski root mudkar neeche badhti hai, jabki shoot mudkar upar badhta hai. Gravity ke is response ko geotropism kehte hain (Fig. 6.9). Roots positively geotropic hain aur shoots negatively geotropic. Andhere box mein side par litaaya seedling yeh saaf dikhata hai: raah dikhaane ke liye light na hone par bhi root tip neeche mudti hai aur shoot tip upar.

Paani aur chemicals bhi growth ki direction tay kar sakte hain. Paani ki taraf growth hydrotropism hai: tapakti pipe ya garden tap ke paas roots geeli mitti ki taraf phailti hain, aur ped ki roots kabhi-kabhi andar ke paani tak pahunchne ke liye naaliyon ko tod deti hain. Kisi chemical ke response mein growth chemotropism hai. Iska jaana-maana example pollen tube hai, jo pollen grain se ovule tak neeche badhti hai, ovule ke chemicals se guide hokar. Isse tum Chapter 7 mein miloge.

Plant responses ko speed ke hisaab se line mein lagao. Chhui-mui ki patti lagbhag ek second mein mudti hai; ek young sunflower apna sir east se west ghumaane mein poora din leta hai; ek shoot ko khidki ki taraf jhukne mein kai din lagte hain. Response jitna tez hona chahiye, uske peeche ka message utni hi tezi se chalna chahiye.

Speed mein electrical impulses jeette hain, aur jahan speed zaroori hai wahan animals inhi ko use karte hain. Lekin wired system ki kuch kamiyaan hain, jo neeche ke comparison mein di gayi hain: yeh sirf un cells tak pahunchta hai jinse nerves judi hain, aur nerve cell ko har impulse ke baad reset hone ke liye rukna padta hai. Kai kaamon ke liye, jaise hafton tak growth ki direction tay karna, aisa message chahiye jo har cell tak pahunche aur lambe samay tak asar karta rahe. Inke liye living things hormones naam ke chemical messengers use karte hain. Hormone use release karne wale cells se phailta hai, aur sirf woh cells respond karte hain jinmein matching receptor molecules hote hain.

Plant hormones

Plants mein growth, development aur light, gravity aur touch ke responses ko coordinate karne ka main tareeka hormones hain. Plant hormone aksar ek jagah banta hai aur diffusion se un cells tak pahunchta hai jinpar woh asar karta hai, kabhi-kabhi kuch doori par.

Sabse jaana-maana plant hormone auxin (ऑक्सिन) hai. Yeh shoot tip mein banta hai aur uske theek neeche ke region mein jaata hai, jahan yeh cells ko lamba karta hai. Ab hum Activity 6.2 samjha sakte hain. Jab shoot par ek side se light padti hai, to auxin light se door, chhaaya wali side par chala jaata hai. Chhaaya wali side ke cells, jinmein zyada auxin hai, roshan side ke cells se zyada lambe hote hain. Jis stem ki ek side doosri se zyada lambi ho, use mudna hi padta hai, aur woh chhoti side ki taraf mudta hai, yaani light wali side ki taraf (Fig. 6.10).

Teen aur hormones list poori karte hain (Table 6.6). Gibberellins bhi auxin ki tarah stems ko lamba karte hain: ganna ugaane wale lambe ganne ke liye inhe spray karte hain, aur angoor ugaane wale bade daanon ke liye. Cytokinins cells ko divide karwate hain, isliye jahan bhi cells tezi se badhte hain, wahan yeh bahut hote hain, jaise develop hote fruits aur seeds mein; nariyal paani iska ek rich natural source hai.

Abscisic acid ulta kaam karta hai, growth par brake ki tarah. Yeh tab jama hota hai jab plant stress mein ho, jaise sookhe mein. Yeh growth dheemi karta hai, iske asar mein leaves ka murjhaana aur budha hona shaamil hai, aur yeh seeds aur buds ko tab tak dormant rakhta hai jab tak haalat behtar na hon.

6.3 Animals mein Hormones

Animals bhi chemical messages use karte hain. Socho tum shaam ko ek shaant gali mein chal rahe ho aur ek kutta bhaunkte hue tumhari taraf daudta hai. Kuch hi seconds mein tumhara dil zor se dhadakne lagta hai, tum tez saans lene lagte ho, aur tumhare pair daudne ke liye taiyaar lagte hain. Tumhe abhi pata nahi ki tum bhaagoge ya wahin khade rehkar kutte ko bhagaoge. Dono haalat mein body ko jaldi se extra energy chahiye, kai organs ke saath kaam karne se.

Taiyaar hone mein heart, lungs, blood vessels aur lagbhag har muscle shaamil hain, itne zyada ki kuch nerves time par sab tak nahi pahunch sakti. Isliye kuch hi pal mein blood ke zariye ek chemical alarm jaata hai. Do adrenal glands, jo har kidney ke upar topi ki tarah baithi hain, bloodstream mein hormone adrenaline daalti hain, aur blood ise har jagah pahunchata hai. Sirf kuch target organs respond karte hain (Fig. 6.12):

• Heart: yeh tez aur zor se dhadakta hai, muscles tak zyada oxygen wala blood pump karta hai.
• Blood vessels: gut aur skin ko supply karne wali chhoti arteries patli ho jaati hain, kyunki unki deewar ki muscles kas jaati hain. Blood uski jagah skeletal muscles ki taraf jaata hai, isiliye dara hua chehra peela dikh sakta hai.
• Saans: diaphragm aur ribs ki muscles zyada mehnat karti hain, isliye tum tez saans lete ho aur zyada oxygen andar lete ho.

Digestion ruk sakta hai; bachna nahi ruk sakta. Is emergency response ko aksar fight or flight kehte hain.

Adrenaline jaise hormones endocrine glands (अंतःस्रावी ग्रंथियाँ) banati hain. In glands mein ducts nahi hote: yeh apne hormones seedhe blood mein daalti hain. (Salivary glands jaisi glands, jo duct se khaali hoti hain, alag tarah ki hain.) Endocrine glands aur unke hormones milkar endocrine system banate hain, jo nervous system ke baad body ko control aur coordinate karne ka doosra tareeka hai.

Plant hormones shoot ko light ki taraf le jaate hain. Animal hormones humein kisi cheez ki taraf nahi badhaate, lekin yeh zaroor control karte hain ki hum kahan aur kitna badhte hain. Jaise-jaise bachcha bada hota hai, haath, pair aur organs ek doosre ke hisaab se sahi size mein rehte hain: dono pair lagbhag bilkul barabar lambe hote hain, aur heart baaki body ke saath-saath badhta hai. Hormones is dhyaan se bane plan ko banaaye rakhne mein madad karte hain.

Iodine aur thyroxin

1950s mein Himalaya ki talhati mein health surveys mein pata chala ki bahut logon ki gardan ke saamne sujan thi. Wajah unke khaane mein thi: wahan ki mitti aur paani mein iodine bahut kam hai. Gardan ke saamne wali thyroid gland ko hormone thyroxin banane ke liye iodine chahiye. Thyroxin tay karta hai ki body ke cells carbohydrates, proteins aur fats ko kis speed se use karein (iska metabolism), aur isse body balanced tarah se badhti hai.

Kaafi iodine na ho to thyroid kaafi thyroxin nahi bana paati, aur sooj sakti hai. Sujan gardan ke saamne ek gaanth ki tarah dikhti hai, theek wahin jahan Fig. 6.13 mein thyroid hai. Is condition ko goitre kehte hain. Ise rokne ke liye aaj India mein bikne wala lagbhag saara namak iodised hota hai.

Growth hormone aur puberty

Pituitary gland, brain ke neeche latakti matar ke daane jitni gland, growth hormone banati hai, jo bachpan aur teenage mein haddiyon aur muscles ki growth chalata hai. Agar bachche mein yeh bahut kam bane, to growth dheemi ho jaati hai aur bachcha bahut chhota reh sakta hai; is condition ko dwarfism kehte hain. Bachpan mein bahut zyada ho to insaan aam se zyada lamba ho sakta hai (gigantism).

Class 5 ki class photo ko Class 9 wali se compare karo. Beech mein ek growth spurt aaya, bagal mein naye baal aaye, aur awaaz aur body shape mein badlaav hue: yeh puberty ke changes hain. Yeh sex hormones se trigger hote hain jo early teens mein behna shuru karte hain: ladkon mein testes se testosterone aur ladkiyon mein ovaries se oestrogen. Yeh hormones body ko reproduction ke liye bhi taiyaar karte hain, jo tum Chapter 7 mein padhoge.

Insulin aur blood sugar

2023 mein publish hui ek ICMR study ke mutaabik India mein 10 crore se zyada log diabetes ke saath jee rahe hain. Diabetes mein blood mein sugar (glucose) ka level bahut zyada bana rehta hai, aur saalon mein yeh aankhon, kidneys, nerves aur heart ko nuksaan pahunchata hai. Jo hormone aam taur par blood sugar kam karta hai, woh insulin hai, jise pancreas banata hai. Kuch diabetic patients mein insulin bahut kam banta hai, isliye doctors dhyaan se diet ke saath insulin injections dete hain.

Feedback hormones ko control mein rakhta hai

Hormones bahut kam maatra mein kaam karte hain, aur zyada hona utna hi nuksaandeh ho sakta hai jitna kam hona. Isliye body ko control karna padta hai ki har hormone kitna aur kab release ho. Yeh kaam feedback mechanism (पुनर्भरण क्रियाविधि) se hota hai: hormone jo result paida karta hai, wahi result tay karta hai ki us hormone ka aur kitna release ho.

Blood sugar dikhata hai ki yeh kaise kaam karta hai (Fig. 6.14). Daal-chawal khaane ke baad digestion se glucose blood mein aata hai aur uska level badhta hai. Pancreas ke cells is badhaav ko sense karte hain aur zyada insulin release karte hain. Insulin body cells ko glucose lene mein aur liver ko use store karne mein madad karta hai, isliye level girta hai. Jaise hi level normal par lautta hai, pancreas yeh bhi sense karta hai aur apna insulin kam kar deta hai. Level ek patli, safe range mein bana rehta hai. Chhat ki paani ki tanki par laga automatic controller bhi aise hi kaam karta hai: paani kam hone par pump on ho jaata hai, aur tanki bharne par controller use off kar deta hai.