Neural Control and Coordination: Class 11 Biology Chapter 18 Hinglish mein

Biology · Hinglish notes, simulations aur practice · Official NCERT chapter PDF ↗

Published 22 Oct 2026 · Updated 22 Oct 2026

55 min
22 practice questions
25 MCQs

Is chapter mein aap kya seekhenge

Samjhao ki coordination kya hai, aur tez, point-to-point neural route ko dheeme hormonal route se compare karo
Trace karo ki Hydra se insects aur phir vertebrates tak neural organisation kaise zyada centralised hota jaata hai
Human neural system ko CNS aur PNS, afferent aur efferent fibres, aur somatic aur autonomic (sympathetic aur parasympathetic) divisions mein classify karo
Neuron ke parts label karo, neurons ko multipolar, bipolar ya unipolar mein baanto, aur myelinated aur non-myelinated fibres ko compare karo
Samjhao ki ion gradients aur sodium–potassium pump resting potential kaise banate hain, aur Na⁺ ka andar aana aur K⁺ ka bahar jaana action potential ko kaise generate aur conduct karta hai
Step by step batao ki impulse electrical aur chemical synapses ko kaise paar karta hai
Brain ki coverings aur forebrain, midbrain aur hindbrain ke parts ke naam batao, har ek ke main kaam ke saath

NCERT Biology Class 11, Chapter 18, pp. 230–238 par based original companion text. Yeh NCERT se juda nahi hai aur NCERT ne ise endorse nahi kiya hai.

Bus stop se nikalne lagi hai, to tum daud padte ho. Kuch hi seconds mein tumhari leg muscles rest ke mukable kai guna tezi se fuel jala rahi hoti hain, aur iske liye unhe extra oxygen chahiye. Tum tez aur gehri saans lene lagte ho, heart rate lagbhag 72 se badhkar shayad 150 beats per minute ho jaata hai, aur pairon tak jaane wali arteries chaudi ho jaati hain taaki zyada blood pahunch sake. Bus mein baith jaane ke baad agle kuch minutes mein yeh sab dheere-dheere wapas normal ho jaata hai. Kisi ek organ ne yeh changes akele nahi kiye. Muscles, lungs, heart, blood vessels aur kidneys tak, sab saath mein, sahi maatra mein aur sahi waqt par badle.

Biologists is teamwork ko coordination (समन्वय) kehte hain: organs ka aapas mein aise kaam karna ki har ek ka kaam baaki sabke kaam ko support kare. Isi tarah body apni andar ki conditions ko steady rakhti hai, jise homeostasis kehte hain, jabki us par demands badalti rehti hain.

Yeh kaam do systems milkar karte hain (Fig. 18.1). Neural system telephone line ki tarah kaam karta hai: ek electrical message cells ki chain se hote hue kisi ek khaas muscle ya gland tak jaata hai aur milliseconds mein pahunch jaata hai. Endocrine system zyada radio broadcast jaisa hai: ek gland blood mein hormone chhodti hai, hormone lagbhag har cell tak pahunchta hai, aur sirf woh cells respond karti hain jinke paas matching receptor hota hai. Hormonal effects dheere shuru hote hain lekin kaafi der tak chal sakte hain. Dono systems milkar organs ko integrate karte hain taaki woh ek saath kaam karein. Is chapter mein hum neural route ko follow karenge: nerve impulse kaise banta hai, kaise travel karta hai aur ek cell se doosre cell tak kaise jaata hai. Chapter 19 mein hormones ki baat hogi.

3/3Blood mein chhoda gaya hormone heart, liver aur muscles tak dheere pahunchta hai.

Fig. 18.1Message bhejne ke do tareeke: nerve ke through ek target tak, ya blood ke through kai targets tak.

Daudte hue insaan ki ek simple outline mein brain aur spinal cord, thigh muscle tak jaati ek nerve, aur kidney ke upar ek adrenal gland dikhaya gaya hai jiske saath blood vessels ka ek loop hai. Step one mein kuch bhi active nahi hai. Step two mein spinal cord se thigh muscle tak jaane wali nerve chamakti hai, uske saath-saath signal dots daudte hain aur ek label par milliseconds aur one target likha hai. Step three mein hormone ke dots adrenal gland se nikal kar blood loop mein jaate hain aur heart, liver aur leg muscles tak pahunchte hain, aur ek label par seconds or longer aur many targets likha hai.

Try karke dekho

Dekho tumhare organs kaise saath-saath chalte hain

Tumhe chahiye

ek ghadi ya phone ki stopwatch
ek partner
ek notebook

Pehle guess karo

Ek minute tak ek hi jagah jogging karne ke turant baad tum kya expect karte ho?

Pulse badhegi, breathing rate same rahegaPulse aur breathing rate dono badhengePulse badhegi, breathing rate ghategaItne kam time mein koi change nahi

Do minute chupchaap baitho. Kalai par 15 seconds tak apni pulse gino aur 4 se multiply karo. Tumhara partner 30 seconds tak tumhari saansein gine aur 2 se multiply kare.
Ek minute tak ek hi jagah jogging karo.
Turant dono ko phir se measure karo.
Baith jao, teen minute ruko aur teesri baar measure karo.

Table 18.1

Kab	Pulse/min	Saansein/min
Rest par
Jogging ke baad
3 min baad

Tumhari entries apne aap save hoti hain.

18.1 Neural System

Har animal ka neural system, jellyfish se lekar human tak, neurons (तंत्रिका कोशिका) se bana hota hai. Yeh cells teen kaamon ke liye specialised hain: stimuli pakadna, doosri cells se signals receive karna aur signals aage bhejna. Ek animal group se doosre tak jo badalta hai woh hai neurons ka arrangement (Fig. 18.2).

Definition

Neuron

Aisa cell jo stimuli detect karne aur signals receive aur transmit karne ke liye specialised hai; neural system ki structural aur functional unit.

ExampleCerebral cortex ka ek neuron.

Hydra ek chhota freshwater cnidarian hai, jismein neurons body wall mein faila hua ek dheela network banate hain. Na koi brain hai, na koi command centre: ek tentacle ko chhoone par signals net mein har direction mein fail jaate hain, aur poora animal sikud jaata hai. Insects mein ek bada step aage dikhta hai. Unke neurons clusters mein ikatthe hote hain jinhe ganglia kehte hain; head mein ek brain hota hai, aur nerve cords aur doosre neural tissue se jude ganglia ki ek chain body ke saath-saath chalti hai. Vertebrates mein sabse developed arrangement hota hai: protective skull ke andar ek bada brain, backbone ke andar spinal cord, aur body ke har hisse tak pahunchti nerves.

3/3Vertebrate: ek brain aur nerves ke saath spinal cord.

Fig. 18.2Nerve net se brain tak: neural organisation zyada centralised hota jaata hai.NCERT p. 231

Teen outlines saath-saath khadi hain: tentacles wala ek Hydra, upar se dikhta ek insect, aur side se dikhta machhli ke shape ka ek vertebrate. Step one mein Hydra highlight hota hai, jismein neurons dots ki tarah bane hain jo lines se judkar uski body mein ek barabar net banate hain, aur koi centre nahi hai. Step two mein insect highlight hota hai, jiske head mein brain hai aur body ke saath-saath nerve cord se judi ganglia ki chain chalti hai. Step three mein vertebrate highlight hota hai, jiske head mein bada brain hai aur peeth ke saath-saath spinal cord chalti hai jisse nerves nikalti hain.

Quick check

3 mein se 1

Hydra ke ek tentacle ko chhoo do to uski poori body sikud jaati hai. Uske neural system ka kaunsa feature ise sabse achhi tarah samjhata hai?

Tentacles ke base par ek brainBody mein faila neurons ka ek networkNerve cord ke saath ganglia ki ek chainPaired nerves wali ek spinal cord

Answer dekho

Answer (B) Body mein faila neurons ka ek network

Hydra mein sirf ek nerve net hota hai, isliye signal poori body mein fail jaata hai aur poori body sikud jaati hai. Nerve cord par ganglia insects mein hote hain, aur spinal cord vertebrates mein.

18.2 Human Neural System

Human neural system ke do parts hain. Brain aur spinal cord milkar central neural system (CNS) banate hain, woh part jo information leta hai, use samajhta hai aur decide karta hai ki body ko kya karna chahiye. Baaki sab, yaani brain aur spinal cord se nikal kar muscles, glands, skin aur organs tak jaane wali nerves, peripheral neural system (PNS) banati hain. Kisi city ka traffic-control room aur har signal aur camera tak jaane wali cables imagine karo: room decide karta hai, cables message le jaati hain (neeche ka comparison).

Compare

CNS aur PNS

CNS

Brain aur spinal cord
Information process karta hai aur commands deta hai
Skull aur backbone ke andar band

PNS

CNS aur baaki body ke beech chalne wali nerves
CNS aur body ke beech impulses le jaata hai
Poori body mein faila hua

PNS ke nerve fibres do directions mein traffic le jaate hain. Afferent fibres (अभिवाही) reports CNS ke andar laate hain: ungli ke sire par pen ka pressure, ya bhare pet ka khinchaav. Efferent fibres (अपवाही) commands CNS se bahar un muscles, glands aur organs tak le jaate hain jinhe respond karna hai. Yaad rakhne ka aasaan tareeka: afferent arrive, efferent exit (Fig. 18.3).

PNS ko is basis par bhi baanta jaata hai ki uske bahar jaane wale impulses kahan jaate hain. Skeletal muscles ke liye messages, yaani woh muscles jinhe tum apni marzi se hilaate ho jab likhte ho ya ball ko kick karte ho, somatic neural system se jaate hain. Autonomic neural system un parts ko serve karta hai jinhe tum apni marzi se nahi hila sakte: involuntary organs aur heart, gut, bladder aur blood vessels ki smooth muscles. Iske do divisions hain, sympathetic aur parasympathetic neural systems, jo aksar ek hi organ par ulti directions mein kaam karte hain: jaise sympathetic side heart ko tez karti hai, aur parasympathetic side use dheema karti hai (Table 18.2).

4/4Autonomic efferent fibres impulses ko heart aur gut tak le jaate hain.

Fig. 18.3Afferent fibres impulses andar laate hain; efferent fibres unhe bahar skeletal muscles (somatic) ya involuntary organs (autonomic) tak le jaate hain.NCERT p. 231

Saamne se dikhti ek body outline mein brain aur spinal cord mote aur nerves patli bani hain. Step one mein CNS aur PNS label hote hain. Step two mein afferent arrows judte hain jo andar ki taraf point karte hain, ek ungli ke sire se aur stomach se spinal cord tak. Step three mein somatic system ka ek efferent arrow judta hai jo spinal cord se bahar upper arm ki muscle tak point karta hai. Step four mein autonomic system ke dashed efferent arrows judte hain jo bahar heart aur gut tak point karte hain.

PNS ke kuch terms travel ki direction ke bajaye serve kiye jaane wale organs ko describe karte hain. CNS ko viscera, yaani chest aur abdomen ke organs, se jodne wali nerves, ganglia aur plexuses (aapas mein guthi nerves ke jaal) ko milakar visceral nervous system kehte hain. Iska traffic dono taraf chalta hai: commands bahar stomach aur bladder jaise organs tak, aur unse reports wapas.PNS nerves CNS se fixed points par nikalti hain: humans mein brain se 12 pairs cranial nerves aur spinal cord se 31 pairs spinal nerves nikalti hain.

Table 18.2Peripheral neural system ke divisions

Division	Impulses kahan le jaata hai	Example
Somatic	CNS → skeletal muscles	school bag uthaate hue tumhari biceps
Autonomic	CNS → involuntary organs aur smooth muscles	stomach wall ki muscle
Sympathetic	autonomic branch; jaise, heart ko tez karta hai	stage show se pehle tez dhadakta heart
Parasympathetic	autonomic branch; jaise, heart ko dheema karta hai	relax karte hue heart ka shaant hona
Visceral	CNS ↔ viscera, dono taraf	gut ki nerves aur plexuses

Quick check

3 mein se 1

Inmein se kaunse PNS ke hisse hain? Jo bhi sahi hon, sab chuno.

Saare sahi options chuno

Answer dekho

Answer

(B) Biceps tak jaati ek nerve
(C) Skin se aata ek afferent fibre
(E) Heart tak jaati ek sympathetic nerve

Nerves aur unke fibres, chahe afferent hon, somatic ya autonomic, PNS banate hain. Spinal cord aur cerebrum CNS ke parts hain.

18.3 Neuron: Neural System ki Structural aur Functional Unit

Neuron itna chhota hota hai ki microscope ke bina dikhta nahi, phir bhi yeh ek saaf plan par bana hai jiske teen main parts hain: ek cell body, kai dendrites aur ek axon (Fig. 18.4).

Shuru karte hain cell body se, jo neuron ka control centre hai. Nucleus ke alawa ismein cell ke saare normal organelles hote hain, aur stain karne par ismein dark clumps dikhte hain jinhe Nissl's granules kehte hain: ribosomes aur rough endoplasmic reticulum ke clusters, yaani neuron ki protein factories.Inka naam German neuroscientist Franz Nissl ke naam par rakha gaya hai, jinhone woh stain banaya jisse yeh dikhte hain. Cell body se dendrites nikalte hain, chhote aur bahut branched fibres ka ek ghana guchha. Inhe neuron ke antennae samjho: yeh signals ikatthe karte hain aur unhe andar cell body tak bhejte hain, aur cell body ki tarah inmein bhi Nissl's granules hote hain.

Signals axon se bahar jaate hain, jo neuron ki output cable hai: ek single lamba fibre jo pair tak jaane wali nerve mein lagbhag ek metre tak lamba ho sakta hai. Sirf apne door wale (distal) end par hi yeh branches mein bantta hai. Har branch ke sire par ek ubhaar hota hai jise synaptic knob kehte hain, jismein synaptic vesicles bhare hote hain, yaani membrane ki chhoti thailiyan jinmein neurotransmitters naam ke chemical messengers hote hain. Yahin signal aage diya jaata hai, ya to ek synapse ke paar doosre neuron ko, ya neuromuscular junction par ek muscle fibre ko. Cell body aur dendrites ke ulat, axon mein Nissl's granules nahi hote.

1/4Impulses dendrites se cell body hote hue axon ke saath-saath chalte hain.

Fig. 18.4Ek multipolar neuron: dendrites impulses andar laate hain, axon unhe bahar synaptic knobs tak le jaata hai.NCERT Fig. 18.1 · p. 232

Ek neuron figure mein left se right tak leta hua hai, aur neeche ek arrow dikhata hai ki impulses left se right travel karte hain. Step one mein poora cell dikhta hai. Step two mein left par cell body highlight hoti hai, apne nucleus aur chhote dark Nissl's granules ke saath, aur uske aas-paas branched dendrites, jin par chhote arrows cell body ki taraf andar point karte hain. Step three mein right ki taraf jaata lamba axon highlight hota hai, jo Schwann cells se bane myelin segments ki ek row mein lipta hai, aur unke beech khule nodes of Ranvier hain. Step four mein right par branched axon terminals highlight hote hain, jinmein har ek ek gol synaptic knob mein khatam hota hai jismein chhote vesicles hain.

Compare

Dendrites aur axon

Dendrites

Aam taur par har neuron mein kai
Chhote, cell body ke paas hi branch hote hain
Impulses ko cell body ki taraf le jaate hain
Inmein Nissl's granules hote hain

Axon

Har neuron mein sirf ek
Lamba, zyaadatar apne door wale end par branch hota hai
Impulses ko cell body se door le jaata hai
Nissl's granules nahi hote; synaptic knobs mein khatam hota hai

Cell body se nikalne wale fibres gino aur tum kisi bhi neuron ko teen types mein se ek mein daal sakte ho (Fig. 18.5). Kai fibres, jinmein ek axon aur baaki dendrites hon, ek multipolar neuron banate hain, jo cerebral cortex mein aam type hai. Theek do, ek dendrite aur ek axon, ek bipolar neuron banate hain, jo jaise aankh ki retina mein milta hai. Ek hi fibre, sirf axon, ek unipolar neuron banata hai; aise neurons zyaadatar embryonic stage mein milte hain.

1/3Multipolar: ek axon, do ya zyada dendrites (cerebral cortex).

Fig. 18.5Cell body se nikalne wale fibres ki ginti ke hisaab se neuron types.NCERT p. 232

Teen neurons saath-saath khade hain, har ek gol cell body aur uske fibres ke saath bana hai, aur har step ek neuron ko highlight karta hai aur ek label batata hai ki woh kahan milta hai. Step one mein multipolar neuron highlight hota hai, jismein kai branched dendrites aur ek axon hai, label cerebral cortex. Step two mein bipolar neuron highlight hota hai, jiski ek side ek dendrite aur doosri side ek axon hai, label retina. Step three mein unipolar neuron highlight hota hai, jismein sirf ek axon hai, label embryonic stage.

Body ki nerves mein axons ki dekhbhaal Schwann cells karti hain, do mein se kisi ek tareeke se (Fig. 18.6). Non-myelinated fibre mein Schwann cell axon ko bas apni membrane ke ek fold mein sambhaal leti hai, koi lapet nahi hoti. Myelinated fibre mein Schwann cell khud ko axon ke chaaron taraf baar-baar lapet leti hai, jaise kisi danda par chatai lapeti jaaye, aur uski membrane ki kai layers milkar ek insulating myelin sheath banati hain. Ek Schwann cell sirf ek chhota hissa cover karti hai, isliye lambe axon par inki ek row hoti hai aur beech mein chhote khule gaps hote hain, jinhe nodes of Ranvier kehte hain. Yeh kahan milte hain: myelinated fibres spinal aur cranial nerves banate hain, jabki non-myelinated fibres autonomic aur somatic neural systems mein aam hain.

3/3Side view: sheath segments aur unke beech khule nodes of Ranvier.

Fig. 18.6Schwann cells ya to axon ko bas gher leti hain ya use aisi myelin sheath mein lapet deti hain jiske beech-beech mein nodes hote hain.NCERT p. 232

Step one mein ek non-myelinated fibre ka cross-section hai: ek Schwann cell ek uthle fold mein axon ko ghere hue hai, aas-paas koi layers nahi. Step two mein ek myelinated fibre ka cross-section hai: ek Schwann cell axon ke chaaron taraf kai baar lipti hai, jisse membrane layers ki ek moti ring, yaani myelin sheath, axon ko gherti hai, aur Schwann cell ka nucleus bahar ki taraf hai. Step three mein ek myelinated axon side se dikhta hai, jo sheath segments ki ek row se dhaka hai, har segment ek Schwann cell se, aur unke beech chhote khule gaps hain jinka label nodes of Ranvier hai.

Quick check

4 mein se 1

Ek slide mein ek neuron ki cell body se paanch branched fibres aur ek lamba fibre nikalta hai. Yeh kis type ka hai, aur aise kai neurons tum kahan expect karoge?

Multipolar; cerebral cortexBipolar; retinaUnipolar; embryoMultipolar; retina

Answer dekho

Answer (A) Multipolar; cerebral cortex

Ek axon aur do ya zyada dendrites se multipolar neuron banta hai, jo cerebral cortex mein typical hai. Retina mein milne wale bipolar neurons mein sirf ek dendrite hota hai.

18.3.1 Nerve Impulse ka Generation aur Conduction

Neuron fire kar hi kyun paata hai? Kyunki rest par bhi uski membrane polarised hoti hai: uski bahari surface par positive charge aur andar ki surface par negative charge hota hai, kuch-kuch battery ke do terminals jaisa. Charge ka yahi stored difference neurons ko excitable cells banata hai. Yeh isliye hota hai kyunki dono taraf ions barabar nahi faile hote, aur yeh asamanta membrane ke ion channels banaaye rakhte hain, yaani protein pores jo chun-chun kar ions ko jaane dete hain.

Resting axon ke dono taraf ke fluids measure karo (Table 18.3) to woh bahut alag milte hain. Axoplasm mein bahar ke fluid se lagbhag 28 guna zyada $K^{+}$ hota hai, jabki bahar lagbhag das guna zyada $N a^{+}$ hota hai; negative charge wale bade protein molecules andar fanse rehte hain. Channels batate hain ki yeh difference bana kyun rehta hai. Rest par kai $K^{+}$ channels khule rehte hain, isliye $K^{+}$ kaafi aasaani se leak ho jaata hai; $N a^{+}$ channels band rehte hain, isliye lagbhag koi $N a^{+}$ paar nahi hota; aur koi bhi channel proteins ko andar-bahar nahi jaane deta. Isliye har ion ek concentration gradient par hota hai, $K^{+}$ bahar leak hone ki koshish mein aur $N a^{+}$ andar ghusne ki koshish mein (Fig. 18.7).

Table 18.3Resting membrane ke aar-paar ions: axoplasm (andar) aur tissue fluid (bahar), mammalian neuron ke typical values mmol/L mein

Ion	Andar	Bahar
$K^{+}$	lagbhag 140	lagbhag 5
$N a^{+}$	lagbhag 15	lagbhag 145
Protein anions	zyada	bahut kam

Leaks in gradients ko dheere-dheere khatam kar dete, isliye cell unhe wapas banane mein energy kharch karti hai. Sodium–potassium pump, ATP se chalne wala ek membrane protein, ions ko unke gradients ke khilaaf move karta hai: har cycle mein yeh teen $N a^{+}$ cell se bahar phenkta hai aur do $K^{+}$ andar laata hai. Isliye har cycle jitne positive charge andar laata hai usse ek zyada bahar bhejta hai. Isme woh $K^{+}$ jodo jo lagaataar bahar leak hota rehta hai jabki negative proteins andar hi reh jaate hain, aur leak aur pump milkar ek steady charge separation banate hain: membrane ke bahar positive, andar negative. Is resting membrane ke aar-paar voltage ko resting potential (विराम विभव) kehte hain, jo ek typical neuron mein lagbhag $- 70 m V$ hota hai. Minus sign batata hai ki andar wali side negative hai, (18.1) ke convention ke hisaab se.

Membrane potential

V_{m} = V_{in} - V_{out}

(18.1)

jahan

$V_{in}, V_{out}$: membrane ke theek andar aur theek bahar ka electrical potential
$V_{m}$: membrane potential; rest par negative kyunki andar wali side negative hai

Definition

Resting potential

Jo neuron impulse conduct nahi kar raha, uski membrane ke aar-paar electrical potential difference; andar wali side bahar ke mukable negative hoti hai.

ExampleEk typical neuron mein lagbhag $- 70 m V$ .

4/4Bahar positive, andar negative: yahi resting potential hai, lagbhag $- 70 m V$ .

Fig. 18.7Leak karte

K^{+}

channels, band

N a^{+}

channels aur pump milkar andar ki side ko negative chhodte hain.NCERT p. 232

Membrane ki ek horizontal patti upar ke tissue fluid ko neeche ke axoplasm se alag karti hai. Step one mein ions dikhte hain: upar kai sodium ions aur kam potassium ions, neeche kai potassium ions, kam sodium ions aur bade negative protein ions. Step two mein ek khula potassium channel hai jisse ek potassium ion upar ki taraf jaata hai, aur uske paas ek band sodium channel hai. Step three mein pump ATP use karke teen sodium ions upar aur bahar, aur do potassium ions neeche aur andar le jaata hai. Step four mein bahari surface par plus signs ki aur andar ki surface par minus signs ki ek row judti hai, aur ek meter minus 70 millivolts padhta hai.

Example 18.1

Pump kitna move karta hai, yeh ginna

Axon membrane ke ek chhote patch mein pumps hain jo milkar har second $5.0 \times 10^{6}$ cycles poore karte hain, aur har cycle mein ek ATP use hota hai. Har second ke liye nikalo (a) kitne $N a^{+}$ ions bahar jaate hain aur kitne $K^{+}$ ions andar aate hain, (b) bahar jaane wale positive charges ki net sankhya, aur (c) woh net charge coulombs mein. $e = 1.6 \times 10^{- 19} C$ lo.

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Ab axon ko ek jagah, P par, ek chhota electric jhatka do, ya kisi sense organ ko use excite karne do (Fig. 18.8). Stimulus wahan ke sodium channels ko khol deta hai, aur ek pal ke liye $N a^{+}$ P par membrane se andar umad padta hai. Sodium ke andar daudne ki do wajah hain: bahar yeh bahut zyada hai, aur negative andar ka hissa ise attract karta hai. Ek millisecond se bhi kaafi kam time mein itne positive ions andar aa jaate hain ki P par charges palat jaate hain, andar positive aur bahar negative. Yeh palatna depolarisation hai, aur P par membrane ke aar-paar ulta voltage, yaani action potential, hi nerve impulse hai.

Definition

Action potential

Neuron ki membrane par stimulate ki gayi jagah par ulta potential difference, jo $N a^{+}$ ke tezi se andar aane se banta hai; yahi nerve impulse hai.

ExampleMembrane potential lagbhag $- 70 m V$ se lagbhag $+ 30 m V$ tak jaata hai aur do-ek milliseconds mein wapas aa jaata hai.

Impulse ko aage kaun le jaata hai? P ko uske resting padosi Q se compare karo. Axon ke andar ab P positive hai aur Q negative; bahar Q positive hai aur P negative. Positive charge + se − ki taraf khiskta hai, isliye current ka ek chhota loop banta hai: andar ki taraf aage, P se Q, aur bahar ki taraf wapas, Q se P. Yeh local current Q ko fire karane ke liye kaafi hai: uske sodium channels khulte hain, sodium andar bhar jaata hai aur Q fire karta hai. Phir Q ka current R ko fire karta hai, R agli jagah ko, aur impulse fibre ke saath-saath girte dominoes ki line ki tarah chalta hai, har ek ko pichhla wala girata hai. Kyunki har jagah apna naya action potential banati hai, isliye impulse ek metre lambe axon ke end tak bhi bina kamzor hue pahunchta hai.

3/4Current andar P se Q ki taraf aur bahar Q se wapas P ki taraf behta hai.

Fig. 18.8Depolarisation ki ek wave: active site par sodium andar aata hai, local currents aage wali site ko depolarise karte hain, aur bahar jaata potassium peeche wali site ko restore karta hai.NCERT Fig. 18.2 · p. 233

Upar ke aadhe hisse mein axon ka ek tukda do membrane lines ki tarah bana hai jis par left se right sites P, Q aur R marked hain; neeche ke aadhe hisse mein axon ke saath position ke against membrane potential ka graph hai, aur minus 70 millivolts par ek dashed line hai. Step one mein resting axon dikhta hai: har jagah bahar plus signs, andar minus signs aur minus 70 par flat graph. Step two mein P par stimulus hai: sodium ions arrows ke saath axon mein jaate hain, P par signs ulat jaate hain aur graph mein P par lagbhag plus 30 tak ek peak hai. Step three mein local current ke curved arrows judte hain: axon ke andar P se Q ki taraf, bahar Q se wapas P ki taraf. Step four mein Q par signs ulte hain, P par potassium ions bahar ja rahe hain aur graph ka peak ab Q par hai, jabki P wapas minus 70 ki taraf ja raha hai.

Har site sirf ek pal ke liye depolarised rehti hai. Sodium channels khulte hi lagbhag turant band ho jaate hain, aur unki jagah potassium channels khulte hain. Andar bharpoor maatra mein maujood $K^{+}$ bahar behta hai, apne saath positive charge le jaata hai, aur andar ki side wapas negative ho jaati hai: yeh repolarisation hai. Ek-do millisecond mein site wapas apne resting potential par aa jaati hai aur phir se fire karne ke liye taiyaar hoti hai. Yahi chhoti si recovery one-way travel ko bhi samjhati hai: jis site ko impulse abhi chhod kar gaya hai woh abhi recover ho rahi hoti hai, isliye wave wapas nahi mud sakti.Is chhote unresponsive time ko refractory period kehte hain.

InteractiveImpulse lab

Ek axon terah membrane sites ki patti ki tarah bana hai, har site ki bahari aur andar ki surface par plus aur minus signs hain, ek site par recording electrode hai aur neeche voltage graph hai. Stimulate dabane par pehli site depolarise hoti hai; Play ya Step time ko aage badhata hai, jisse sodium ka andar aana har site ko baari-baari ulat deta hai, potassium ka bahar jaana peeche ki sites ko restore karta hai, aur graph electrode par membrane potential ko minus 70 se lagbhag plus 30 millivolts tak chadhte aur wapas girte dikhata hai. Ek switch fibre ko myelinated bana deta hai, jismein sirf nodes of Ranvier fire karte hain aur impulse node se node koodta hai, aur ek readout end tak pahunchne mein lage time ko compare karta hai.

Fig. 18.9Stimulate dabao, phir Play ya Step dabao, aur impulse ko travel karte dekho; fibre ko myelinated par switch karo aur lagne wale time ko compare karo.

Myelin picture badal deta hai. Sheath ek achha insulator hai, isliye myelinated fibre mein ions sirf nodes of Ranvier par hi membrane paar kar sakte hain. Ek active node ka local current sheath ke neeche tezi se failta hai aur agle node ko depolarise kar deta hai, aur impulse node se node koodta hua lagta hai. Yeh saltatory conduction (Latin saltare, yaani koodna) non-myelinated fibre ki lagaataar, site-by-site conduction se kahin zyada tez hai. Tumhari body ke sabse tez myelinated fibres lagbhag $100 m / s$ par conduct karte hain, jabki patle non-myelinated fibres lagbhag $1 m / s$ hi kar paate hain. Isse energy bhi bachti hai, kyunki pumps ko kam ions wapas rakhne padte hain. Signal ko lagne wala time (18.2) se milta hai.

Conduction time

t = \frac{d}{v}

(18.2)

jahan

$d$: fibre ki woh length jo impulse travel karta hai, metres mein
$v$: fibre ki conduction speed, metres per second mein

Example 18.2

Myelin aur message ki speed

Tumhare pair ke angoothe se ek touch signal spinal cord tak $0.90 m$ travel karta hai. Isme lagne wala time nikalo (a) $60 m / s$ par conduct karne wale myelinated fibre mein aur (b) usi length ke $1.2 m / s$ par conduct karne wale non-myelinated fibre mein. (c) Myelinated route kitne guna tez hai?

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Quick check

4 mein se 1

Rest par axon membrane

negatively charged proteins ke liye poori tarah permeable hoti hai

N a^{+}

aur

K^{+}

ke liye barabar permeable hoti hai

K^{+}

ke liye zyada permeable aur

N a^{+}

ke liye lagbhag impermeable hoti hai

K^{+}

se zyada

N a^{+}

ke liye permeable hoti hai

Answer dekho

Answer (C) $K^{+}$ ke liye zyada permeable aur $N a^{+}$ ke liye lagbhag impermeable hoti hai

Rest par membrane

K^{+}

ko kaafi aasaani se jaane deti hai lekin

N a^{+}

ke liye lagbhag band hoti hai; zyada

N a^{+}

permeability stimulated state ki baat hai. Protein anions to bilkul paar nahi kar sakte.

18.3.2 Impulses ka Transmission

Neurons wire ki tarah sire se sira nahi jude hote; har ek alag cell hai. Isliye jab impulse axon ke sire par pahunchta hai, to use ek junction ke paar agli cell ko saunpna padta hai. Yeh junction, yaani synapse (अंतर्ग्रथन), ki do sides hoti hain: pre-synaptic neuron, jiska terminal impulse laata hai, aur post-synaptic neuron, jo use receive karta hai. Dono membranes lagbhag chhooti hain ya ek patle gap, yaani synaptic cleft, se alag rehti hain, isi se tay hota hai ki hand-over kaise hoga, aur isi se do tarah ke synapse milte hain (Electrical aur chemical synapses).

Definition

Synapse

Do neurons ke beech ka junction, jahan bhejne wale (pre-synaptic) neuron ki membrane receive karne wale (post-synaptic) neuron ki membrane se milti hai aur impulse paar jaata hai.

Electrical synapse mein gap lagbhag gayab ho jaata hai. Dono membranes itni paas dabi hoti hain ki aate hue impulse ka local current seedha agle neuron mein beh jaata hai,Current gap junctions se paar hota hai, yaani patle protein channels jo dono cells ke cytoplasm ko jodte hain. bilkul waise hi jaise woh ek hi axon ke agle hisse mein behta. Na kuch release karna padta hai na kuch pehchaanna, isliye yeh sabse tez possible hand-over hai, kisi bhi chemical synapse se tez. Lekin tumhara neural system ise kabhi-kabhi hi use karta hai.

Tumhare zyaadatar synapses chemical synapses hain. Yahan cleft ek asli, fluid se bhara gap hai, jo local current ke paar karne ke liye bahut chauda hai, isliye iske bajaye ek chemical messenger signal ko paar le jaata hai (Fig. 18.10):

Action potential axon terminal tak pahunchta hai.
Synaptic vesicles pre-synaptic membrane ki andar wali surface ki taraf khinchte hain, usmein mil jaate hain aur apna neurotransmitter cleft mein chhod dete hain.
Neurotransmitter molecules patle cleft ke paar jaate hain aur post-synaptic membrane par unke liye bane receptors se jud jaate hain.
Har bhara hua receptor ek ion channel kholta hai, aur ions post-synaptic neuron mein bhar jaate hain.
Ions ka flow receive karne wali membrane ka voltage badal deta hai. Agar yeh change us neuron ko fire karne ki taraf dhakelta hai, to yeh excitatory hai; agar neuron ko rokta hai, to inhibitory hai.

3/4Neurotransmitter cleft paar karta hai aur specific receptors se bind karta hai.

Fig. 18.10Chemical synapse par ek neurotransmitter signal ko cleft ke paar le jaata hai.NCERT Fig. 18.3 · p. 234

Pre-synaptic neuron ka phoola hua axon terminal left se aata hai, gol synaptic vesicles se bhara; ek patla vertical synaptic cleft use right ki post-synaptic membrane se alag karta hai, jis par receptor sites hain. Step one mein axon ke saath aata ek impulse arrow dikhta hai. Step two mein vesicles pre-synaptic membrane tak pahunch kar usse fuse hote hain aur neurotransmitter dots cleft mein chhodte hain. Step three mein neurotransmitter dots right ke receptors se jude dikhte hain. Step four mein post-synaptic membrane ke ion channels khule hain, ions andar beh rahe hain, aur ek label par new potential, excitatory ya inhibitory likha hai.

Acetylcholine ek jaana-maana neurotransmitter hai; aur bhi kai hain. Is design ke do nateeje yaad rakhne layak hain. Sirf pre-synaptic side neurotransmitter store karti hai aur sirf post-synaptic side par receptors hote hain, isliye chemical synapse signals ko sirf ek direction mein bhejta hai. Aur release, diffusion aur binding mein time lagta hai, isliye har chemical synapse lagbhag aadhe millisecond ka synaptic delay jodta hai.

Compare

Electrical aur chemical synapses

Electrical

Membranes bahut paas-paas
Current seedha ek cell se doosre cell mein jaata hai
Zyada tez
Humans mein kam milta hai

Chemical

Membranes fluid se bhare synaptic cleft se alag
Ek neurotransmitter signal ko paar le jaata hai
Dheema: har ek thoda delay jodta hai
Humans mein zyaadatar synapses

Example 18.3

Time kahan jaata hai?

Brain mein ek signal paanch neurons ki chain se guzarta hai, isliye woh chaar chemical synapses paar karta hai. Chain ke axons milkar $0.12 m$ lambe hain aur $40 m / s$ par conduct karte hain, aur har synapse $0.5 m s$ ka delay jodta hai. (a) Total time nikalo. (b) Iska kitna hissa synapses par lagta hai? (c) Agar chaaron electrical synapses hote jinka delay negligible hai, to total ka andaaza lagao.

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Try karke dekho

Tumhara neural system kitna tez hai?

Tumhe chahiye

ek 30 cm ka ruler
ek partner

Pehle guess karo

Tumhara partner bina bataaye ek ruler girata hai aur tum use pakadte ho. Tumhara reaction time sabse kareeb kiske hoga?

0.002 s0.02 s0.2 s2 s

Apni forearm table ke kinaare par tikao, haath khula rakho, angootha aur pehli ungli lagbhag 2 cm door.
Tumhara partner ruler ko seedha khada pakadta hai, uska 0 cm ka nishan tumhare angoothe ke upar wale hisse ke barabar.
Bina bataaye tumhara partner ruler chhod deta hai. Ruler ko jitni jaldi ho sake pakdo aur angoothe ke upar wala nishan padho.
Paanch baar repeat karo. Har catch distance $d$ (metres mein) ko $t = \sqrt{2 d / g}$ se reaction time mein badlo, $g = 9.8 m / s^{2}$ lekar.

Table 18.4

Trial	d (cm)	t (s)
1
2
3
4
5

Tumhari entries apne aap save hoti hain.

18.4 Central Neural System

Tumhara har decision, aur hazaaron aise jo tum notice bhi nahi karte, brain se hokar guzarte hain, jo body ka central information processor aur uska command and control system hai. Iske kaamon ki ek chhoti list:

Conscious kaam: dekhna, sunna, bolna, yaad rakhna, sochna aur emotions mehsoos karna, aur woh intelligence jo in sabko jodti hai
Movement: har voluntary action, aur chalte-phirte body ka balance banaye rakhna
Andar ka kaam jo tum notice nahi karte: heart, lungs aur kidneys jaise zaroori involuntary organs ko chalana, body temperature steady rakhna, aur bhookh aur pyaas ka signal dena
Timing: body ke 24-hour (circadian) rhythms, jaise sleep–wake cycle
Management: kai endocrine glands ko direct karna, aur behaviour ko shape karna

Haddi aur membranes is naram organ ki hifaazat karti hain. Skull bahar ka sakht case hai. Uske neeche teen membranes, jinhe cranial meninges (मस्तिष्कावरण) kehte hain, brain ko parcel ki layers ki tarah lapetti hain (Fig. 18.11). Bahar se andar chalein to dura mater ('tough mother') moti aur mazboot hai; arachnoid, jiska naam uske makdi ke jaale jaise texture se pada, bahut patli hai; aur pia mater ('tender mother') ek naazuk parat hai jo brain tissue se chipki rehti hai aur uske har fold ke saath chalti hai. Brain se bahar ki taraf initials PAD banate hain: pia, arachnoid, dura.

4/4Pia mater: brain tissue ko chhooti andar wali layer.

Fig. 18.11Bahar se andar cranial meninges: dura mater, arachnoid, pia mater.NCERT p. 235

Sir ka ek curved slice close-up mein dikhaya gaya hai, upar skull aur neeche brain ki folded surface. Step one mein sirf skull aur brain dikhte hain. Step two mein skull ke theek neeche moti bahari dura mater judti hai aur label hoti hai. Step three mein dura ke neeche patli, jaale jaisi arachnoid judti hai. Step four mein pia mater judti hai, ek patli layer jo brain surface ke har fold ke saath chalti hai, aur is tarah teeno meninges order mein label ho jaati hain.

Definition

Cranial meninges

Skull ke andar brain ko dhakne wali teen membranes: bahari dura mater, patli beech wali arachnoid aur andar wali pia mater.

Poore brain ko dekhein to iske teen bade regions hain, jinke naam shuruaati embryo mein aage se peeche unke order par rakhe gaye hain: forebrain, midbrain aur hindbrain (Fig. 18.12).

4/5Hindbrain: pons, cerebellum aur medulla oblongata.

Fig. 18.12Brain ke teen divisions, aur brain stem.NCERT Fig. 18.4 · p. 235

Midline se dikhta ek simple aadha brain right ki taraf face karta hai, sir ka aage wala hissa right par aur spinal cord neeche se nikalti hui. Step one mein outline hai aur saare parts halke rangon mein hain. Step two mein forebrain highlight hota hai: upar bada cerebrum, uske andar mehraab jaisa corpus callosum, aur neeche thalamus aur hypothalamus. Step three mein thalamus ke neeche chhota midbrain highlight hota hai, jiske beech se cerebral aqueduct guzarta hai aur peeche corpora quadrigemina hain. Step four mein hindbrain highlight hota hai: aage pons, peeche folded cerebellum, aur spinal cord se judta medulla. Step five mein midbrain, pons aur medulla ko milakar brain stem ki tarah outline kiya jaata hai.

18.4.1 Forebrain

Forebrain teen structures se banta hai: cerebrum, thalamus aur hypothalamus. Human brain mein cerebrum baaki sab se kahin bada hai. Upar se dekhne par iske do bade halves dikhte hain, left aur right cerebral hemispheres, jo maathe se sir ke peeche tak jaane wale ek gehre groove se alag hote hain. Us groove ke tal par nerve fibres ka ek chauda pul, corpus callosum, dono halves ko jodta hai taaki woh ek ki tarah kaam kar sakein (Fig. 18.13).

Har hemisphere par kuch millimetres moti neurons ki ek parat hoti hai, cerebral cortex, jo ridges aur grooves mein sikudi hoti hai. Yeh sikudan ek bahut badi sheet ko skull ki seemit jagah mein fit kar deti hai, jaise ek dupatta chhote bag mein fit hone ke liye mud-tud jaata hai. Neuron cell bodies se bhara hone ke kaaran cortex ka rang halka grey hota hai aur ise grey matter kehte hain. Iske neeche white matter hota hai: nerve fibres ke bundles jinki fatty myelin sheaths ise safed sa dikhati hain.

3/3Bahar grey matter (cell bodies); andar white matter (myelinated tracts).

Fig. 18.13Corpus callosum se jude cerebral hemispheres: bahar grey cortex, andar white matter.NCERT p. 236

Cerebrum ka ek slice aage se dikhta hai, jo saath-saath rakhe do gol halves jaisa hai. Step one mein dono halves hain, jin par left aur right hemisphere label hai, aur upar ek gehri cleft unhe alag karti hai. Step two mein corpus callosum highlight hota hai, fibres ki ek patti jo cleft ke neeche hemispheres ke beech jaati hai. Step three mein har hemisphere ka folded bahari kinaara grey matter aur andar ka hissa white matter ki tarah shade hota hai, dono ke labels ke saath.

Cortex ka map banao to teen tarah ke ilaake milte hain. Sensory areas sense organs ki reports receive karte hain, aur motor areas muscles ko hilaane wale commands dete hain. Baaki, jo cortex ka bada hissa hai, in dono mein se koi kaam seedha nahi karta. Yeh association areas oonche level ka kaam karte hain, jaise kai senses ke input ko jodna, memories store karna aur communication sambhalna. Jab phone par ek jaani-pehchaani awaaz sunte hi tumhe apne cousin ka chehra yaad aa jaata hai, tab association areas jo tum sun rahe ho use jo tumhe yaad hai usse jod rahe hote hain.

Hemispheres ke neeche chhupa hai thalamus, ek relay hub jahan sensory aur motor signals cortex tak aate-jaate coordinate hote hain. Iske theek neeche lagbhag ek badaam ke size ka structure hai jiske kaam bahut saare hain, hypothalamus. Yeh tumhara thermostat hai, jo body temperature steady rakhta hai; yeh tumhe bhookh ya pyaas mehsoos karata hai; aur iske kuch neurons neurosecretory cells hain jo hypothalamic hormones release karte hain (Chapter 19).Hypothalamus mein body ki master clock bhi hoti hai, neurons ka ek chhota cluster jise suprachiasmatic nucleus kehte hain, jo circadian rhythms ko din aur raat ke saath time mein rakhta hai.

Emotions ki apni circuitry hoti hai. Limbic system (ya limbic lobe) hemispheres ke sabse andar ke hisson aur unse jude gehre structures se banta hai, jinmein amygdala aur hippocampus shaamil hain. Hypothalamus ke saath milkar yeh motivation aur sexual behaviour ko control karta hai aur yeh shape karta hai ki hum emotions kaise express karte hain: cricket final se pehle ka excitement, khushi, gussa, darr. Yeh smell ki sense aur autonomic responses mein bhi hissa leta hai.

Quick check

3 mein se 1

Cerebral cortex ko grey matter kehte hain kyunki

ismein myelinated fibres bahut hote hainyeh cerebrospinal fluid se bhara hota haipia mater ise dhakti haineuron cell bodies wahan ikatthi hoti hain

Answer dekho

Answer (D) neuron cell bodies wahan ikatthi hoti hain

Cortex mein bhari cell bodies use grey dikhati hain. Myelinated fibres andar wale white matter ko safed banate hain.

18.4.2 Midbrain

Thalamus aur hypothalamus ke neeche, aur pons ke upar, brain ka ek chhota segment hai, midbrain. Iske beech se cerebrospinal fluid ki ek patli naali guzarti hai, cerebral aqueduct. Iski peeche wali (dorsal) surface par chaar gol ubhaar hote hain, corpora quadrigemina (literal matlab 'chaar judwa bodies'). Aankhon, kaanon aur skin se aane wale signals yahan milte hain aur jode jaate hain.In lobes ka upar wala pair zyaadatar vision se aur neeche wala pair sunne se juda hai.

18.4.3 Hindbrain

Hindbrain ke teen parts hain: pons, cerebellum aur medulla oblongata (aam taur par sirf medulla). Pons, jiska Latin mein matlab 'bridge' hai, zyaadatar nerve fibres ke bundles se bana hai jo brain ke ek part ko doosre se jodte hain. Iska ek centre, pneumotaxic centre, medulla dwara set kiye gaye breathing rhythm ko bhi moderate karta hai, jaisa tumne Chapter 14 mein dekha.

Cerebellum pons ke peeche, cerebrum ke peeche wale hisse ke neeche hota hai. Iski surface cortex se bhi zyada baareek folds mein mudi hoti hai, jisse bahut saare neurons ke liye jagah banti hai: yeh brain ke mass ka sirf lagbhag dasvaan hissa hai, phir bhi brain ke har paanch mein se lagbhag chaar neurons ismein hote hain. Cerebellum inner ear ki semicircular canals aur auditory system se aane wali information ko jodta hai, aur tumhe balanced aur tumhari movements ko smooth rakhta hai, chahe tum bheed bhare market mein cycle chala rahe ho ya hilti hui local train mein khade ho.

Sabse neeche medulla patla hote hue spinal cord mein badal jaata hai. Chhota hone par bhi zindagi ispar nirbhar hai: iske centres tumhari saans chalaate hain, cardiovascular reflexes ke through heart rate aur blood pressure adjust karte hain, aur gastric secretion control karte hain, isiliye yahan chot jaanleva ho sakti hai. Midbrain, pons aur medulla milkar brain stem banate hain, woh dandi jis par baaki brain tika hai aur jiske through woh spinal cord se juda hai.

Table 18.5Ek nazar mein brain ke parts

Part	Main kaam
Cerebrum (forebrain)	sochna, memory, voluntary movement, senses, bolna
Thalamus (forebrain)	sensory aur motor signals coordinate karta hai
Hypothalamus (forebrain)	temperature, bhookh, pyaas; hypothalamic hormones
Limbic system (forebrain)	emotions, motivation, sexual behaviour, smell
Corpora quadrigemina (midbrain)	visual, tactile aur auditory inputs ko integrate karte hain
Pons (hindbrain)	brain regions ko jodne wale fibre tracts
Cerebellum (hindbrain)	balance aur smooth, coordinated movement
Medulla oblongata (hindbrain)	saans, heart aur blood-vessel reflexes, gastric secretion

Flash cards · 8

Yeh kaam kaunsa part karta hai?

1 / 8

Recap

Summary aur key points

Coordination se organs ek saath adjust karte hain; neural system yeh tezi se aur point to point karta hai, endocrine system hormones ke through (shuruaat).
Neural organisation Hydra ke nerve net se lekar insects ke brain aur ganglia tak, aur vertebrates ke brain aur spinal cord tak jaata hai (Section 18.1).
CNS (brain aur spinal cord) information process karta hai; PNS use afferent (andar ki taraf) aur efferent (bahar ki taraf) fibres ke through body se jodta hai (Section 18.2).
Somatic nerves skeletal muscles ko serve karti hain; autonomic nerves involuntary organs aur smooth muscles ko serve karti hain aur sympathetic aur parasympathetic divisions banati hain (Table 18.2).
Neuron mein Nissl's granules wali cell body, impulses andar laane wale dendrites aur unhe bahar synaptic knobs tak le jaane wala axon hota hai (Section 18.3).
Neurons multipolar (cerebral cortex), bipolar (retina) ya unipolar (zyaadatar embryonic) hote hain; axons myelinated, nodes of Ranvier ke saath, ya non-myelinated hote hain (Fig. 18.6).
Selective ion channels aur pump (teen $N a^{+}$ bahar, do $K^{+}$ andar) resting axon ki andar wali side ko negative rakhte hain: yahi resting potential hai (Section 18.3.1).
Stimulus $N a^{+}$ ko andar daudne deta hai aur polarity ulat deta hai: yahi action potential, yaani nerve impulse hai (Fig. 18.8).
Local currents agli site ko depolarise karte hain, bahar jaata $K^{+}$ resting potential wapas laata hai, aur myelinated fibres node se node koodkar zyada tez conduct karte hain (saltatory conduction).
Electrical synapses current ko seedha aur tezi se paar karte hain; chemical synapses par ek neurotransmitter cleft paar karta hai, receptors se bind karta hai aur ion channels kholta hai, jisse excitatory ya inhibitory potential banta hai (Section 18.3.2).
Skull aur teen meninges se protected brain mein forebrain, midbrain aur hindbrain hote hain (Section 18.4).
Forebrain mein cerebrum (corpus callosum se jude do hemispheres; white matter ke upar grey cortex), thalamus aur hypothalamus hain, aur limbic system emotion aur motivation ko control karta hai (Section 18.4.1).
Midbrain mein cerebral aqueduct aur corpora quadrigemina hote hain; hindbrain mein pons regions ko jodta hai, cerebellum balance rakhta hai aur medulla mein vital centres hote hain; midbrain, pons aur medulla milkar brain stem banate hain (Section 18.4.3).

Apna NCERT exercise question dhoondo

Hamare practice questions ncert.ai ke liye likhe gaye hain aur NCERT exercises ko follow karte hain. Apni textbook ke question se match karne wala question dhoondo; uska answer uske saath hai.

Tumhari NCERT textbook mein	Yahan practice question
NCERT Exercises Q1	Practice Q1
NCERT Exercises Q2	Practice Q2
NCERT Exercises Q3	Practice Q3
NCERT Exercises Q4	Practice Q4
NCERT Exercises Q5	Practice Q5
NCERT Exercises Q6 (aur Q5 e)	Practice Q6
NCERT Exercises Q7	Practice Q7
NCERT Exercises Q8	Practice Q8
NCERT Exercises Q9	Practice Q9
NCERT Exercises Q10	Practice Q10

Quick check: MCQs

18.1 Neural System3 questions
18.2 Human Neural System3 questions
18.3 Neuron: Neural System ki Structural aur Functional Unit4 questions
18.3.1 Nerve Impulse ka Generation aur Conduction4 questions
18.3.2 Impulses ka Transmission4 questions
18.4.1 Forebrain3 questions
18.4.3 Hindbrain4 questions

Glossary · 15

Key terms (English + Hindi)

action potential: Neuron ki membrane par stimulate ki gayi site par ulta potential difference, jo $N a^{+}$ ke andar daudne se banta hai; yahi nerve impulse hai.Chapter mein pehli baar yahan aaya →
afferent fibreअभिवाही तंतुabhivahi tantu: Aisa nerve fibre jo impulses ko tissues aur organs se CNS tak le jaata hai.Chapter mein pehli baar yahan aaya →
autonomic neural systemस्वायत्त तंत्रिका तंत्रswayatt tantrika tantra: PNS ka woh part jo impulses ko CNS se involuntary organs aur smooth muscles tak le jaata hai; iske sympathetic aur parasympathetic divisions hain.Chapter mein pehli baar yahan aaya →

central neural systemकेंद्रीय तंत्रिका तंत्रkendriya tantrika tantra: Brain aur spinal cord, jahan information process hoti hai aur control kiya jaata hai.Chapter mein pehli baar yahan aaya →
coordinationसमन्वयsamanvay: Organs ka apni activity ek saath adjust karna taaki har ek baaki sabke kaam ko support kare.Chapter mein pehli baar yahan aaya →
corpus callosum: Nerve fibres ka chauda tract jo left aur right cerebral hemispheres ko jodta hai.Chapter mein pehli baar yahan aaya →

efferent fibreअपवाही तंतुapvahi tantu: Aisa nerve fibre jo commands ko CNS se bahar tissues aur organs tak le jaata hai.Chapter mein pehli baar yahan aaya →

meningesमस्तिष्कावरणmastishkavaran: Brain ko dhakne wali teen membranes: dura mater, arachnoid aur pia mater.Chapter mein pehli baar yahan aaya →
myelin sheath: Axon ke chaaron taraf ek insulating lapet, jo Schwann cell membrane ki layers se banti hai.Chapter mein pehli baar yahan aaya →

neuronतंत्रिका कोशिकाtantrika koshika: Aisa cell jo stimuli detect karne aur signals receive aur transmit karne ke liye specialised hai; neural system ki unit.Chapter mein pehli baar yahan aaya →
neurotransmitter: Synaptic vesicles se release hone wala chemical jo signal ko chemical synapse ke paar le jaata hai.Chapter mein pehli baar yahan aaya →
node of Ranvier: Axon ke saath do paas-paas ki myelin sheaths ke beech ka chhota khula gap.Chapter mein pehli baar yahan aaya →

peripheral neural systemपरिधीय तंत्रिका तंत्रparidhiya tantrika tantra: Brain aur spinal cord ko baaki body se jodne wali saari nerves.Chapter mein pehli baar yahan aaya →

resting potentialविराम विभवviram vibhav: Jo neuron impulse conduct nahi kar raha, uski membrane ke aar-paar potential difference; andar wali side negative hoti hai.Chapter mein pehli baar yahan aaya →

synapseअंतर्ग्रथनantargrathan: Do neurons ke beech ka junction, jo pre-synaptic aur post-synaptic membranes se banta hai.Chapter mein pehli baar yahan aaya →

Neural Control and Coordination: Class 11 Biology Chapter 18 Hinglish mein

Is chapter mein aap kya seekhenge

18.1 Neural System

18.2 Human Neural System

18.3 Neuron: Neural System ki Structural aur Functional Unit

18.3.1 Nerve Impulse ka Generation aur Conduction

18.3.2 Impulses ka Transmission

18.4 Central Neural System

18.4.1 Forebrain

18.4.2 Midbrain

18.4.3 Hindbrain

Summary aur key points

Practice questions answers ke saath (NCERT “Exercises”)

Apna NCERT exercise question dhoondo

Quick check: MCQs

Key terms (English + Hindi)

Tum chapter ke end tak pahunch gaye