Class 10 Science

Chapter 6: Control and Coordination

Learn how the nervous system, brain, plant hormones, and endocrine glands work together to keep living organisms responsive and balanced.

🌐 Language / भाषा:

Remember from before:

In Class 9, we learned that nervous tissue coordinates body movements and responds to stimuli. Class 9 में, हमने सीखा था की nervous tissue body movements को coordinate करता है और stimuli के according respond करता है.
We saw that specialized cells called neurons are structural and functional units of nervous tissue. हमने देखा की specialized cells jinhein neurons kehte हैं, वह nervous tissue की structural और functional units होती हैं.
Visible movements (like a cat running, swings going up and down) are often responses to changes in the environment to keep the organism safe. Visible movements (जैसे cat का run करना, swings का up-down hona) hamare surroundings के changes का response होती हैं जो हमें safe रखता है.

1. Animals - Nervous System 1. Animals - Nervous System (जंतु-तंत्रिका तंत्र)

Section Goal: Explain how nervous tissue detects environmental stimuli and transmits electrical impulses from neurons to muscle cells. Section Goal: Nervous tissue kaise environmental stimuli को detect करता है और neurons से muscle cells तक electrical impulses को transmit करता है, ise समझें.

🔌 The Telegraph Network Analogy

Imagine a school building with wires running from every classroom to a central speaker. The sensory receptors are like microphones, the neurons are the copper wires carrying electrical signals, and the muscles are speakers that play the sound. The nervous system is a fast-speed biological wire network. Ek school building की kalpana करें jahan हर classroom से wires ek central speaker तक ja रही हैं. Sensory receptors (ग्राही) microphones ki tarah hain, neurons copper wires की तरह हैं जो electrical signals ले jati हैं, और muscles speakers की तरह हैं जो sound play करते हैं. Humara nervous system ek fast-speed biological wire network की तरह है.

All information from our environment is detected by the specialized tips of some nerve cells, which are called receptors [NCERT p.99]. These receptors are located in our sense organs: हमारे environment की सारी information nerve cells की specialized tips द्वारा detect की जाती है, jinhein receptors (ग्राही) kehte hain [NCERT p.99]। ये receptors हमारे sense organs में होते हैं:

Gustatory receptors (रससंवेदी ग्राही) detect taste [NCERT p.99]. Gustatory receptors (रससंवेदी ग्राही) taste detect karte hain [NCERT p.99]।
Olfactory receptors (घ्राणग्राही) detect smell [NCERT p.99]. Olfactory receptors (घ्राणग्राही) smell detect karte hain [NCERT p.99]।
Photoreceptors in eyes detect light, and Phonoreceptors in ears detect sound. Eyes में present photoreceptors light detect करते हैं, और ears में present phonoreceptors sound detect करते हैं.

A neuron (तंत्रिका कोशिका) is the functional unit of the nervous system. Information acquired at the dendritic tip of a neuron sets off a chemical reaction that creates an electrical impulse [NCERT p.100]. Ek neuron (तंत्रिका कोशिका) nervous system ki basic functional unit hai. Neuron ke dendritic tip par mili information ek chemical reaction ko start karti hai jisse ek electrical impulse create hota hai [NCERT p.100]।

3D Neuromuscular Junction Synapse Render

Source: Adapted from NCERT Class 10 Science, Fig 6.1 (b) Neuromuscular Junction, p. 100.

The electrical impulse travels from the dendrite to the cell body (Cyton) and then along the axon to its end [NCERT p.100]. At the end of the axon, the electrical impulse sets off the release of some chemical neurotransmitters. These chemicals cross the gap, called a synapse, and start a similar electrical impulse in the next neuron's dendrite [NCERT p.100]. ये electrical impulse dendrite से cell body (Cyton) तक travel करता है और फिर axon से होते hue uske end तक पहुंचता है [NCERT p.100]। Axon के end पर, electrical impulse chemical neurotransmitters को release करता है. ये chemicals dono nerve cells के बीच के gap, जिसे synapse (अंतर्ग्रथन) kehte hain, ko cross karte hain aur next neuron ke dendrite mein ek similar electrical impulse start karte hain [NCERT p.100]।

Finally, when the nerve impulse reaches a muscle, the muscle must move. A neuromuscular junction is the junction where the nerve ending meets a muscle fiber [NCERT p.100]. Muscle cells change their shape to cause movement. They have special proteins that change their shape and arrangement in the cell in response to electrical impulses, causing contraction [NCERT p.102]. Finally, जब nerve impulse muscle तक पहुंचता है, तो muscle move करती है. Neuromuscular junction (तंत्रिका-पेशी संधि) wo point hai jahan nerve ending ek muscle fiber se milti hai [NCERT p.100]। Movement के लिए muscle cells अपना shape बदलती हैं. उनके पास special proteins होते हैं जो electrical impulses के response में अपना shape और cell में अपना arrangement बदलते हैं, jisse contraction होता है [NCERT p.102]।

🔬 Lab 1: Virtual Neuron Synaptic Cleft 🔬 Lab 1: Virtual Neuron Synaptic Cleft (सिनैप्स लैब)

Drag the slider below to propagate an electrical signal along a nerve fiber and watch it cross the chemical synapse cleft to stimulate the next neuron. Nerve fiber के along electrical signal send करने के लिए slider को drag करें और dekhein kaise ये chemical synapse cleft को cross karke next neuron को stimulate करता है.

Signal Progress: 0%

⚡ Checkpoint 1 ⚡ Checkpoint 1

Which receptors are specialized to detect taste and smell respectively? Taste और smell को detect करने के लिए kaunse specialized receptors उसे होते हैं?

📝 Section Summary

Receptors like gustatory (taste) and olfactory (smell) detect information from our surroundings. Gustatory (taste) और olfactory (smell) जैसे receptors हमारे surrounding से information detect करते हैं.
Impulses travel electrically down the dendrite, cyton, and axon, then cross the synapse gap chemically via neurotransmitters. Impulses electrically travel करते हैं down थे dendrite, cyton, और axon, और synapse gap को chemical neurotransmitters के through cross करते हैं.
Muscles contract when receiving nerve impulses by changing the shape and layout of their specialized proteins. Nerve impulses milne पर muscles specialized proteins का shape और arrangement badalkar contract करती हैं.

2. Reflex Actions 2. Reflex Actions (प्रतिवर्ती क्रिया)

Section Goal: Trace the pathway of a reflex arc and explain why automatic reflex actions bypass conscious brain processing for survival. Section Goal: Reflex arc के pathway को trace करें और समझें की survival के लिए automatic reflex actions brain के conscious process bypass क्यों करते हैं.

🚨 The Smoke Detector & Automatic Sprinkler

If a room catches fire, the automatic water sprinkler goes off immediately on its own. It does not wait for a fire truck to arrive or for a committee to vote. A reflex action is your body's automatic local sprinkler—acting instantly to prevent damage before the brain finishes thinking. अगर किसी room में aag lag jaye, तो automatic water sprinkler turant khud-b-khud chal jata है. वह fire truck के आने या किसी committee की permission का wait nahi करता. Ek reflex action भी आपकी body का automatic sprinkler है—जो brain के sochne से पहले ही damage rokne के लिए instantly act करता है.

A reflex action is a sudden, involuntary response to an environmental stimulus, such as pulling your hand back instantly when touching a hot flame [NCERT p.100]. Ek reflex action (प्रतिवर्ती क्रिया) environmental stimulus ke liye ek sudden aur involuntary response hai, jaise hot flame ko touch karte hi hand ko instantly peeche kheench lena [NCERT p.100]।

Thinking is a complex process involving dense networks of thousands of neurons in the brain. If we touched a hot object and waited for our brain to think "it is hot, I should move my hand," the tissue would burn. To prevent this, the connection between input (sensory) nerves and output (motor) nerves is made directly in the spinal cord [NCERT p.101]. Thinking ek complex process है jisme brain के thousands of neurons का network kaam करता है. अगर हम किसी hot object को touch करें और brain के sochne का wait करें की "ye garm है, mujhe hand hatana chahiye", तो tissue burn हो jayega. Is damage को rokne के लिए, input (sensory) nerves और output (motor) nerves का connection direct spinal cord (मेरुरज्जु) mein kar kiya jata hai [NCERT p.101]।

The pathway that detects a stimulus, routes it through the spinal cord, and activates an effector muscle is called a reflex arc [NCERT p.101]. Stimulus को detect करने, उसे spinal cord के through route करने, और effector muscle को activate करने वाले pathway को reflex arc (प्रतिवर्ती चाप) kehte hain [NCERT p.101]।

The Reflex Arc Sequence:
Stimulus (Heat) → Receptor (Skin) → Sensory Neuron → Spinal Cord (Relay Neuron) → Motor Neuron → Effector (Muscle) → Response (Pull hand away) [NCERT p.101]. The Reflex Arc Sequence:
Stimulus (Garm) → Receptor (Skin) → Sensory Neuron → Spinal Cord (Relay Neuron) → Motor Neuron → Effector (Muscle) → Response (Hand hatana) [NCERT p.101]।

🔬 Lab 2: Interactive Reflex Arc Timeline 🔬 Lab 2: Interactive Reflex Arc Timeline (रिफ्लेक्स आर्क लैब)

Click the "Stimulate" button to send an emergency electrical impulse through the reflex arc and see how the spinal cord triggers muscle contraction before the brain is notified. "Stimulate" button पर click karke reflex arc के through impulse send करें और dekhein kaise spinal cord brain को पाता चलने से पहले ही muscle contraction trigger कर देता है.

⚡ Checkpoint 2 ⚡ Checkpoint 2

What is the correct pathway sequence of an electrical impulse in a reflex arc? Reflex arc में electrical impulse का correct pathway sequence kya है?

📝 Section Summary

Reflex actions bypass the conscious brain networks to allow rapid, life-saving responses to danger. Reflex actions conscious brain networks को bypass करते हैं taaki danger के time rapid और life-saving response mil सके.
Reflex arcs are formed in the spinal cord, and sensory signals are simultaneously sent up to the brain. Reflex arcs spinal cord में बनते हैं, और sensory signals simultaneously brain तक भी bheje जाते हैं.
The sequence is: Receptor → Sensory Neuron → Spinal Cord → Motor Neuron → Effector Muscle. Correct sequence है: Receptor → Sensory Neuron → Spinal Cord → Motor Neuron → Effector Muscle.

3. Human Brain 3. Human Brain (मानव मस्तिष्क)

Section Goal: Identify the three major divisions of the brain and describe how each anatomical region regulates voluntary and involuntary bodily functions. Section Goal: Brain के teen major divisions की pehchan करें और समझें की हर region voluntary और involuntary functions को kaise control करता है.

🏢 The Corporate Headquarters Analogy

Think of the brain as a massive headquarters office:
• Forebrain (Cerebrum) is the CEO's office, where voluntary, conscious plans, memory, and thoughts are decided.
• Midbrain & Hindbrain (Pons, Medulla) are the maintenance basements controlling automatic utilities (AC, power grid, breathing, heartbeat) in the background.
• Cerebellum is the fitness trainer ensuring employees walk in straight lines and maintain perfect balance. Brain को ek massive corporate headquarters office की तरह समझें:
• Forebrain (Cerebrum) CEO का office है, jahan voluntary और conscious plans, memory, और thoughts decide होते हैं.
• Midbrain & Hindbrain (Pons, Medulla) maintenance basements हैं जो background में automatic utilities (breathing, heartbeat) को control करते हैं.
• Cerebellum fitness trainer है जो ensure करता है की आप straight line में चलें और body balance maintain rakhein.

The brain and spinal cord constitute the Central Nervous System (CNS) [NCERT p.101]. The peripheral nerves arise from the CNS: Cranial nerves originate from the brain, and Spinal nerves originate from the spinal cord [NCERT p.101]. Brain और spinal cord मिलकर Central Nervous System (CNS) (केंद्रीय तंत्रिका तंत्र) banate hain [NCERT p.101]। Isse peripheral nerves निकलती हैं: Cranial nerves brain से originate होती हैं, और Spinal nerves spinal cord से originate होती हैं [NCERT p.101]।

Source: Adapted from NCERT Class 10 Science, Fig 6.3 Human Brain, p. 102.

The brain is divided into three major anatomical regions: Brain को teen major anatomical regions में divide किया गया है:

A. Forebrain (अग्रमस्तिष्क) A. Forebrain (अग्रमस्तिष्क)

The forebrain consists mainly of the Cerebrum (प्रमस्तिष्क). It is the main thinking part of the brain and controls all voluntary actions [NCERT p.101]. It contains sensory areas for hearing, smell, sight, and separate areas for learning and memory [NCERT p.101]. It also houses the hunger center that senses when we are full [NCERT p.102]. Forebrain main part Cerebrum (प्रमस्तिष्क) se bana hota hai. Ye brain ka main thinking area hai jo saari voluntary actions ko control karta hai [NCERT p.101]। Isme hearing, smell, sight के लिए sensory areas होते हैं, और learning और memory के लिए separate areas होते हैं [NCERT p.101]। Isme hunger center भी होता है जो feed complete hone पर fullness feel कराता है [NCERT p.102]।

B. Midbrain (मध्यमस्तिष्क) & Hindbrain (पश्चमस्तिष्क) B. Midbrain (मध्यमस्तिष्क) & Hindbrain (पश्चमस्तिष्क)

These regions control involuntary actions (like pupil size changes, salivation, heartbeat) [NCERT p.102]. The hindbrain is split into three specific parts: ये regions involuntary actions (जैसे pupil size change hona, salivation, heartbeat) control करते हैं [NCERT p.102]। Hindbrain teen parts में split होता है:

Pons (पोंस) regulates respiration [NCERT p.102]. Pons (पोंस) respiration (श्वसन) ko regulate karta hai [NCERT p.102]।
Medulla (मध्यांश) controls blood pressure, salivation, and vomiting reflexes [NCERT p.102]. Medulla (मध्यांश) blood pressure, salivation, aur vomiting reflexes ko control karta hai [NCERT p.102]।
Cerebellum (अनुमस्तिष्क) is responsible for precision of voluntary actions and maintaining posture and body balance (like walking in a straight line, riding a bicycle, or picking up a pencil) [NCERT p.102]. Cerebellum (अनुमस्तिष्क) voluntary actions ki precision aur body posture aur balance maintain karne ke liye responsible hai (jaise straight line mein chalna, bicycle chalana, ya pencil uthana) [NCERT p.102]।

C. Protection of the CNS C. Protection of the CNS (सुरक्षा)

Because the brain is extremely delicate, it sits inside a bony box called the cranium (कपाल) [NCERT p.102]. Within the skull, the brain is suspended in a fluid-filled balloon containing Cerebrospinal Fluid (CSF), which acts as a shock absorber [NCERT p.102]. The spinal cord is protected by the vertebral column or backbone [NCERT p.102]. Kyunki brain bahut delicate है, ये ek bony box के अंदर safe रहता है जिसे cranium (कपाल) kehte hain [NCERT p.102]। Skull के अंदर, brain fluid-filled balloon के अंदर suspended होता है jisme Cerebrospinal Fluid (CSF) होता है, जो shock absorber का kaam करता है [NCERT p.102]। Spinal cord ko spinal column ya backbone (कशेरुका दंड) protect karti hai [NCERT p.102]।

🔬 Lab 3: Brain Function Mapping Atlas 🔬 Lab 3: Brain Function Mapping Atlas (मस्तिष्क मानचित्र)

Click on the buttons below to highlight different regions of the brain and discover what voluntary and involuntary actions they regulate. Brain के different regions को highlight करने के लिए buttons पर click करें और janein की वह voluntary और involuntary actions को kaise regulate करते हैं.

Select a Brain Region Select a Brain Region (ब्रेन का हिस्सा चुनें)

Click on one of the colored buttons above to see how that specific section of the central nervous system controls thoughts, movements, or automatic survival reflexes. Upar दिए गए colored buttons पर click karke dekhein की central nervous system का वह part thoughts, movements या automatic survival reflexes को kaise control करता है.

⚡ Checkpoint 3 ⚡ Checkpoint 3

Which part of the hindbrain controls posture and balance during voluntary movements like riding a bicycle? Voluntary movements (जैसे bicycle chalana) के time posture और body balance hindbrain का kaunsa part control करता है?

📝 Section Summary

The Forebrain (Cerebrum) is the center for thinking, decision making, voluntary actions, and memory. Forebrain (Cerebrum) thinking, decision making, voluntary actions, और memory का main center है.
The Hindbrain consists of the Pons (breathing), Medulla (vomiting, salivation, BP), and Cerebellum (balance, coordination). Hindbrain में Pons (breathing), Medulla (vomiting, saliva, BP), और Cerebellum (balance, coordination) होते हैं.
The brain is protected by a bony cranium skull and floating cerebrospinal fluid (CSF) shock absorbers. Brain cranium skull और floating cerebrospinal fluid (CSF) shock absorbers द्वारा protected रहता है.

4. Coordination in Plants 4. Coordination in Plants (पादपों में समन्वय)

Section Goal: Contrast plant immediate responses (turgor changes) with slow directional growth (tropisms) driven by chemical phytohormones. Section Goal: Plants के immediate responses (turgor changes) और slow directional growth (tropisms) के बीच difference समझें, जो chemical phytohormones द्वारा controlled होते हैं.

🌱 The Solar Tracker and Touch Sensor

Animals run away from danger using muscles. Plants cannot walk, so they move by growing. Bending towards a window is like an automatic solar panel slowly turning towards the sun. Folding leaves on a touch-sensitive plant (chhui-mui) is like deflating water balloons inside leaf joints, causing them to drop instantly. Animals muscles का उसे karke danger से भाग सकते हैं. Plants chal nahi सकते, isliye वह grow karke move करते हैं. Window की taraf bend hona solar panel के sun की taraf turn hone jaisa है. Touch-sensitive plant (chhui-mui) की leaves का fold hona leaf joints के अंदर के water balloons के deflate hone jaisa है, jisse leaves instantly drop हो jati हैं.

Plants have neither a nervous system nor muscles [NCERT p.102]. They coordinate their actions through two distinct types of movements: Plants के पास na तो nervous system होता है और na ही muscles [NCERT p.102]। Ve do distinct types के movements के द्वारा coordinate करते हैं:

A. Immediate Response to Stimulus (वृद्धि से मुक्त गति) A. Immediate Response to Stimulus (वृद्धि से मुक्त गति)

This movement is independent of growth [NCERT p.102]. When you touch the leaves of the sensitive plant (Mimosa pudica / छुई-मुई), they fold up immediately [NCERT p.102]. The plant uses electrochemical means to convey information from cell to cell. Instead of muscle proteins, plant cells change their shape by changing the amount of water in them—swelling (when water enters) or shrinking (when water leaves), causing the leaves to fold [NCERT p.103]. ये movement growth पर depend nahi करती [NCERT p.102]। Jab aap sensitive plant (Mimosa pudica / छुई-मुई) ki leaves ko touch karte hain, toh wo instantly fold ho jati hain [NCERT p.102]। Plant cell-तो-cell information convey करने के लिए electrochemical means उसे करते हैं. Muscle proteins के बिना, plant cells water volume change karke अपना shape बदलती हैं—water enter करने पर swell हो jati हैं और exit करने पर shrink हो jati हैं, jisse leaves fold होती हैं [NCERT p.103]।

Source: Adapted from NCERT Class 10 Science, Fig 6.5 & 6.6 Phototropism and Geotropism, p. 104.

B. Directional Growth Movements — Tropisms (तटस्थ गतियां) B. Directional Growth Movements — Tropisms (तटस्थ गतियां)

These are growth movements in response to directional environmental stimuli [NCERT p.104]: ये growth movements directional environmental stimuli के response में होती हैं [NCERT p.104]:

Phototropism (प्रकाशानुवर्तन): Growth response to light. Shoots bend towards light (+), while roots bend away (-) [NCERT p.104]. Phototropism (प्रकाशानुवर्तन): Light ke direction mein response. Stems light ki taraf bend hote hain (+), jabki roots light se door bend hoti hain (-) [NCERT p.104]।
Geotropism (गुरुत्वानुवर्तन): Response to gravity. Roots grow downwards (+), and shoots grow upwards (-) [NCERT p.104]. Geotropism (गुरुत्वानुवर्तन): Gravity ke direction mein response. Roots niche grow karti hain (+), aur shoots upar grow karte hain (-) [NCERT p.104]।
Hydrotropism (जलाकर्षण): Roots grow towards water sources. Hydrotropism (जलाकर्षण): Roots ka moisture aur water sources ki taraf grow karna.
Chemotropism (रसायनअनुवर्तन): Response to chemicals, such as the growth of pollen tubes towards ovules during fertilization [NCERT p.104]. Chemotropism (रसायनअनुवर्तन): Chemicals ke direction mein growth response, jaise fertilization ke dauran pollen tubes का ovules की taraf grow करना [NCERT p.104]।

C. Plant Hormones (Phytohormones / पादप हार्मोन) C. Plant Hormones (Phytohormones / पादप हार्मोन)

Plants synthesize chemical compounds to coordinate growth and development [NCERT p.105]: Plants growth और development coordinate करने के लिए chemical compounds synthesize करते हैं [NCERT p.105]:

Hormone Hormone (पादप हार्मोन)	Primary Biological Action Primary Biological Action (जैविक क्रिया)	NCERT Citation NCERT Citation
Auxin (ऑक्सिन) Auxin (ऑक्सिन)	Synthesized at shoot tip. Promotes cell elongation. Diffuses to the shaded side when light shines from one direction, causing cells on the dark side to grow longer, bending the stem towards light. Shoot tip पर synthesize होता है. Cell elongation को promote करता है. जब light ek side से आती है, तो ये shaded side में diffuse हो jata है, jisse dark side की cells लंबी grow करती हैं और stem light की taraf bend हो jata है.	[NCERT p.105]
Gibberellins (जिबरेलिन) Gibberellins (जिबरेलिन)	Help in the growth of the stem. Stems की length और growth में help करते हैं.	[NCERT p.105]
Cytokinins (साइटोकाइनिन) Cytokinins (साइटोकाइनिन)	Promote rapid cell division. Found in high concentrations in areas of rapid growth (fruits and seeds). Rapid cell division को promote करते हैं. Fruits और seeds जैसे zones में high concentration में मिलते हैं.	[NCERT p.105]
Abscisic Acid (एब्सिसिक अम्ल) Abscisic Acid (एब्सिसिक अम्ल)	Inhibits growth. Causes wilting of leaves and closing of stomata during water stress. Growth को inhibit करता है. Leaves के murjhane (wilting) और dry times में stomata close करने के लिए responsible है.	[NCERT p.105]

🔬 Lab 4: Plant Tropism growth Sandbox 🔬 Lab 4: Plant Tropism growth Sandbox (पादप ट्रॉपिज्म)

Adjust the direction of the light bulb using the slider to see how auxin accumulation on the shaded side causes cell elongation and bends the shoot towards the light. Light bulb की direction slider से change करें और dekhein kaise shaded side में auxin accumulation से cell growth बढ़ती है और stem bend हो jata है.

Light Position (Left ↔ Right): Center

⚡ Checkpoint 4 ⚡ Checkpoint 4

Which plant hormone inhibits growth and is responsible for the wilting of leaves? Kaunsa plant hormone growth को inhibit करता है और leaves के wilting के लिए responsible है?

📝 Section Summary

Plant leaves fold immediately upon touch via local changes in turgor water pressure. Touch करने पर water pressure (turgor pressure) के change hone से sensitive leaves instantly fold हो jati हैं.
Tropic growth responses curve stems towards light (phototropism) and roots downwards with gravity (geotropism). Directional tropic growth stems को light की taraf curve करती है (phototropism) और roots को gravity की taraf (geotropism).
Hormones (Auxin, Gibberellins, Cytokinins) promote growth, while Abscisic Acid inhibits growth. Auxins, Gibberellins, और Cytokinins growth को promote करते हैं, jabki Abscisic Acid growth inhibit करता है.

5. Animal Hormones 5. Animal Hormones (जंतुओं में हार्मोन)

Section Goal: Explain how endocrine glands secrete hormones into the bloodstream and describe the feedback mechanisms that control hormone concentrations. Section Goal: Endocrine glands kaise hormones को direct blood में secrete करती हैं और उनके level को feedback mechanisms से kaise control किया jata है, ise समझें.

✉️ The Wireless Radio Broadcast Analogy

Nerves are like copper telephone wires. The endocrine system is like a radio broadcast tower. Endocrine glands release chemical hormones directly into the blood river (the broadcast). Only cells with the correct matching protein antenna (receptors) receive the message and respond. Nerves copper telephone wires की तरह हैं. Endocrine system wireless radio broadcast tower की तरह है. Endocrine glands chemical hormones को direct blood river (circulation) में release करती हैं. सिर्फ wahi cells response देती हैं jinje पास correct matching protein receptor antenna होता है.

Hormones are chemical messengers secreted directly into the bloodstream by ductless endocrine glands to regulate metabolic and physiological activities [NCERT p.106]. Hormones chemical messengers होते हैं जो ductless endocrine glands (अंतःस्रावी ग्रंथियाँ) dwara direct blood stream mein release kiye jaate hain, taaki metabolic aur physiological functions ko regulate kiya ja sake [NCERT p.106]।

Source: Adapted from NCERT Class 10 Science, Fig 6.7 Endocrine Glands in humans, p. 106.

Key Endocrine Glands and Their Hormones: Key Endocrine Glands and Their Hormones (मुख्य अंतःस्रावी ग्रंथियां):

1. Adrenaline (एड्रीनालिन) - Adrenal Glands 1. Adrenaline (एड्रीनालिन) - Adrenal Glands

Secreted by adrenal glands during stress or emergency (the "fight-or-flight" response) [NCERT p.105].
Effects: Heart beats faster to supply more oxygen to muscles, breathing rate increases, and blood flow is diverted from the digestive system and skin to skeletal muscles [NCERT p.105]. Adrenal glands से emergency या stress के time secrete होता है (fight-or-flight response) [NCERT p.105]।
Effects: Heart beat fast हो jati है taaki muscles को oxygen supply mil सके, breathing rate बढ़ jati है, और blood flow digestive tract और skin से divert hokar skeletal muscles तक पहुंचता है [NCERT p.105]।

2. Thyroxine (थाइरॉक्सिन) - Thyroid Gland 2. Thyroxine (थाइरॉक्सिन) - Thyroid Gland

Regulates carbohydrate, protein, and fat metabolism to provide the optimal balance for growth [NCERT p.105].
Iodine Requirement: Iodine is essential for the synthesis of thyroxine [NCERT p.105]. A deficiency of iodine in our diet leads to Goitre (घेंघा रोग), characterized by a swollen neck [NCERT p.106]. Growth को regulate करने के लिए carbohydrate, protein, और fat के metabolism को control करता है [NCERT p.105]।
Iodine Requirement: Thyroxine के synthesis के लिए iodine ज़रूरी है [NCERT p.105]। Diet में iodine की kami से Goitre (घेंघा रोग) ho jata hai, jisme neck swell ho jati hai [NCERT p.106]।

3. Growth Hormone (वृद्धि हार्मोन) - Pituitary Gland 3. Growth Hormone (वृद्धि हार्मोन) - Pituitary Gland

Secreted by the pituitary gland (located at the base of the brain) to regulate growth and development [NCERT p.106].
Deficiency in childhood causes dwarfism (बौनापन), while excess causes gigantism (अतिदीर्घकाय) [NCERT p.106]. Brain के base पर located pituitary gland (पीयूष ग्रंथि) se secrete hota hai aur growth ko regulate karta hai [NCERT p.106]।
Childhood में iski deficiency से dwarfism (बौनापन) aur excess se gigantism (अतिदीर्घकाय) ho jata hai [NCERT p.106]।

4. Insulin (इंसुलिन) - Pancreas 4. Insulin (इंसुलिन) - Pancreas

Produced by the pancreas to regulate blood glucose levels [NCERT p.107]. A deficiency in insulin production leads to Diabetes, where blood sugar levels rise to harmful levels [NCERT p.107]. Pancreas (अग्न्याशय) se produce hota hai jo blood glucose levels ko control karta hai [NCERT p.107]। Insulin की kami से Diabetes (मधुमेह) ho jata hai, jisme blood sugar level tezi se badhta hai [NCERT p.107]।

Feedback Mechanism (पुनर्भरण क्रियाविधि) Feedback Mechanism (पुनर्भरण क्रियाविधि)

It is crucial that hormones are secreted in precise quantities. The timing and amount of hormone release are regulated by chemical feedback mechanisms [NCERT p.107]. Hormones का body में right quantity में release hona ज़रूरी है. Iske timing और amount को feedback mechanisms (पुनर्भरण क्रियाविधि) chemical control ke through maintain karti hain [NCERT p.107]।

When blood sugar levels rise, they are detected by cells of the pancreas, which respond by secreting more insulin [NCERT p.107]. As the blood sugar level falls to normal, insulin secretion is shut off [NCERT p.107]. E.g., जब blood sugar level बढ़ता है, तो pancreas की cells उसे detect करती हैं और insulin secretion badha देती हैं [NCERT p.107]। जैसे ही blood sugar level normal होता है, insulin secretion wapas control (shut off) हो jata है [NCERT p.107]।

🔬 Lab 5: Homeostasis Glucose Feedback Loop 🔬 Lab 5: Homeostasis Glucose Feedback Loop (होमियोस्टैसिस लैब)

Trigger actions below to see how insulin coordinates blood sugar regulation through a biological feedback loop. नीचे दिए buttons पर click करें और dekhein kaise body insulin और feedback loop से blood sugar regulate करती है.

⚡ Checkpoint 5 ⚡ Checkpoint 5

Which mineral is essential for the synthesis of the hormone thyroxine by the thyroid gland? Thyroid gland द्वारा thyroxine hormone के synthesis के लिए kaunsa mineral ज़रूरी है?

📝 Section Summary

Hormones are chemical coordinates released directly into the blood by endocrine glands. Hormones chemical coordinates हैं जो endocrine glands द्वारा direct blood stream में release होते हैं.
Thyroxine regulates metabolic speed and requires iodine; insulin regulates glucose and is secreted by the pancreas. Thyroxine body metabolic rate maintain करता है और उसे iodine चाहिए; insulin sugar regulate करता है और pancreas से secrete होता है.
Hormone concentration is tightly regulated by negative feedback loops that detect change and restore balance. Hormone concentration feedback loops द्वारा control होती है जो balance restore करने के लिए checks apply करती हैं.

NCERT Solutions NCERT Solutions (पाठ्यपुस्तक के हल)

Q1. What is the difference between a reflex action and walking? Q1. Reflex action और walking के बीच kya difference है?

Answer:

Reflex Action: It is a rapid, automatic, and involuntary response to sensory stimuli (e.g. pulling hand away from heat). It is controlled by the spinal cord and does not require conscious thinking. Reflex Action: Ye ek rapid, automatic, aur involuntary response hai stimuli ke response mein (जैसे hot plate se hand hatana)। Ye spinal cord dwara control hota hai aur isme conscious thinking ki zaroorat nahi hoti.
Walking: It is a voluntary action coordinated by the brain (specifically the cerebellum in the hindbrain). It is a learned behavior that is controlled by conscious intent and complex muscular coordinates. Walking: ये ek voluntary action है जिसे brain (specifically hindbrain का cerebellum) coordinate करता है. Isme conscious intent और muscle coordination ज़रूरी है.

Q2. What happens at the synapse between two neurons? Q2. Do neurons के बीच synapse पर kya होता है?

Answer: At the end of the axon of the first neuron, the electrical impulse triggers the release of chemical messengers called neurotransmitters. These chemicals diffuse across the tiny physical gap (synapse) and bind to specific receptor sites on the dendrite of the next neuron. This binding sets off a new electrical impulse in the second neuron, allowing the signal to travel forward. Answer: First neuron के axon end पर, electrical impulse chemical messengers (neurotransmitters) को release करता है. ये chemicals tiny synaptic gap (synapse) के cross diffuse hokar next neuron के dendrite receptors पर bind होते हैं. Is binding से next neuron में ek naya electrical impulse start होता है, jisse signal forward travel करता है.

Q3. Which part of the brain maintains posture and equilibrium of the body? Q3. Body का posture और balance (equilibrium) maintain करने के लिए brain का kaunsa part responsible है?

Answer: The Cerebellum, which is a part of the Hindbrain, is responsible for maintaining posture, body balance, and equilibrium during voluntary actions. Answer: Hindbrain का Cerebellum part body posture, physical balance, और equilibrium को coordinate करता है voluntary actions के dauran.

Q4. How do we detect the smell of an agarbatti (incense stick)? Q4. अगरबत्ती (incense stick) की smell hume kaise detect होती है?

Answer: Agarbatti smoke carries chemical vapors which are detected by the olfactory receptors located inside our nasal chamber. These receptors trigger electrical impulses that travel along sensory neurons to the olfactory center in the forebrain (cerebrum). The cerebrum interprets this input and recognizes the smell based on previous memory. Answer: अगरबत्ती smoke के chemical vapors nasal chamber में present olfactory receptors (घ्राणग्राही) dwara detect kiye jaate hain. Ye receptors electrical impulses coordinate karte hain jo sensory neurons ke raste forebrain ke cerebrum section तक पहुंचते हैं, jahan previous memories के according smell की identity decode होती है.

Q5. What is the role of the brain in reflex action? Q5. Reflex actions में brain का kya role होता है?

Answer: The reflex action itself bypasses conscious brain processing and is executed directly via a reflex arc in the spinal cord for speed. However, the sensory pathway continues upwards to the brain. The brain registers the stimulus event, processes the sensation (e.g. pain), and stores the event in memory to prevent future encounters. Answer: Reflex action fast action के लिए conscious brain processing को bypass karke direct spinal cord के through coordinate होता है. लेकिन sensory information parallel में brain तक भी jati है, taaki brain pain register कर सके और is incident की memory को future protection के लिए save rakh सके.

Q6. What are plant hormones? Q6. Plant hormones (पादप हार्मोन) kya hote hain?

Answer: Plant hormones (or phytohormones) are organic chemical substances synthesized in minute quantities in one part of a plant and translocated to other parts, where they coordinate growth, development, cell division, and responses to environmental stimuli. Examples: Auxin, Gibberellin, Cytokinin, and Abscisic Acid. Answer: Plant hormones (या phytohormones) organic chemical substances होते हैं जो plants के parts में tiny quantities में synthesize होते हैं और different locations तक travel karke growth, cell division, development, और stimuli response coordinate करते हैं. E.g., Auxin, Gibberellin, Cytokinin, और Abscisic Acid.

Q7. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light? Q7. Sensitive plant (chhui-mui) की leaves की movement shoot की phototropic movement से kaise different है?

Answer:

Sensitive Plant (Chhui-mui) movement Sensitive Plant (Chhui-mui) movement	Phototropic movement of shoot Phototropic movement of shoot
Growth-independent (Nastic movement). Growth-independent (Nastic movement - वृद्धि से मुक्त गति)।	Growth-dependent (Tropic movement). Growth-dependent (Tropic movement - वृद्धि पर निर्भर गति)।
Immediate response driven by turgor water pressure changes inside pulvini cells. Immediate response जो pulvini cells में water volume (turgor pressure) के बदलने से होता है.	Slow growth curvature response driven by unequal distribution of the hormone auxin. Slow growth curvature response जो hormone auxin के unequal distribution के karan होता है.
Non-directional response to mechanical touch. Non-directional response जो किसी touch stimulus के response में होता है.	Directional response towards light source. Directional response जो light source की taraf curve growth दिखाता है.

Q8. How does phototropism occur in plants? Q8. Plants mein phototropism (प्रकाशानुवर्तन) kaise hota hai?

Answer: Phototropism is driven by the hormone auxin. Auxin is synthesized at the shoot tips. When light falls on the plant from one side, auxin diffuses away from the light towards the shaded side of the stem. The higher concentration of auxin on the shaded side causes cells on that side to grow longer than those on the illuminated side, causing the stem tip to curve and bend towards the light. Answer: Phototropism hormone auxin द्वारा controlled होता है. Auxin shoot tips पर synthesize होता है. जब light ek side से आती है, तो auxin diffuse hokar shaded (dark) side में shift हो jata है. Shaded side में auxin concentration high hone से wahan की cells normal cell से ज़्यादा elongation करती हैं, jisse shoot tip light direction में curve हो jata है.

Q9. How are the brain and spinal cord protected? Q9. Brain और spinal cord की protection kaise होती है?

Answer:

The brain is housed within a rigid, bony structure called the cranium (skull) and suspended inside a fluid-filled balloon containing cerebrospinal fluid (CSF) which acts as a hydraulic shock absorber. Brain skull bony structure cranium (कपाल) ke andar fluid-filled shock-absorbing Cerebrospinal Fluid (CSF) balloon में safe रहता है.
The spinal cord is enclosed and protected within the hard, articulated bony channel of the vertebral column (backbone). Spinal cord backbone channel vertebral column (कशेरुका दंड) ke protective bony tunnel ke andar safety paati hai.

Q10. How does chemical coordination take place in animals? Q10. Animals में chemical coordination kaise होता है?

Answer: Chemical coordination is mediated by hormones secreted by endocrine glands. These ductless glands release hormones directly into the blood circulation. Blood carries the hormones to target organs, where they bind to specific cell receptors, triggering metabolic changes that coordinate growth, blood pressure, sugar levels, and homeostasis. Answer: Chemical coordination endocrine glands से release hone वाले hormones के through होता है. ये ductless glands directly blood circulation में hormones release करती हैं. Blood इन hormones को target organs तक ले jata है, jahan receptors से bind hokar ये growth, BP, blood sugar level, और homeostasis को coordinate करते हैं.

Q11. Why is the use of iodised salt recommended? Q11. Iodised salt (आयोडीन युक्त नमक) use karne ki recommendation kyun di jaati hai?

Answer: The thyroid gland requires iodine to synthesize the hormone thyroxine. Thyroxine is crucial for regulating carbohydrate, fat, and protein metabolism to promote balanced bodily growth. A lack of iodine in diet prevents thyroxine synthesis, causing Goitre, characterized by an enlarged, swollen thyroid gland. Answer: Thyroid gland को thyroxine hormone banane के लिए iodine ज़रूरी है. Thyroxine body growth के लिए fat, carbohydrate, और protein metabolism को balance करता है. Diet में iodine की kami से Goitre हो jata है, jisme neck region (thyroid) tezi से swell हो jati है.

Q12. How does our body respond when adrenaline is secreted into the blood? Q12. Adrenaline blood में release hone पर body kaise respond करती है?

Answer: Adrenaline prepares the body for action under threat (fight-or-flight):

Heart rate and stroke volume increase, boosting blood oxygenation to skeletal muscles. Heart rate and pumping load बढ़ jate हैं, taaki skeletal muscles को continuous oxygen flow mil सके.
Respiration rate increases due to contraction of diaphragm and rib muscles. Diaphragm and rib muscles के heavy contraction से respiration rate बढ़ jata है.
Blood supply to the skin and digestive system is constricted, diverting flow to active skeletal muscles. Digestive system और skin तो blood supply narrow (constrict) हो jati है, taaki blood major working muscles तक shift हो सके.
Starch conversion to glucose increases in the liver to supply immediate metabolic energy. Immediate metabolic energy output के लिए liver stored glycogen reserves को glucose में release करता है.

Solved PYQs Solved PYQs (विगत वर्षों के प्रश्न)

[1 Mark] Name the plant hormone that inhibits growth and causes wilting of leaves. [1 Mark] Growth inhibit करने वाले और leaves की wilting के लिए responsible plant hormone का name बताएं.

Answer: Abscisic Acid (ABA) is the phytohormone responsible for growth inhibition and leaf wilting. Answer: Abscisic Acid (ABA) ही growth inhibition और leaves wilting के लिए responsible plant hormone है.

[2 Marks] Mention two functions of the hormone insulin. Name the gland that secretes it. [2 Marks] Hormone insulin के do functions बताएं. उसे secrete करने वाली gland का name भी लिखें.

Answer:

It regulates blood glucose levels by promoting cellular glucose uptake. ये cells में glucose intake को regulate karke blood glucose level normal करता है.
It stimulates the liver to convert excess glucose into glycogen for storage. ये liver cells को excess sugar glycogen में store करने के लिए instructions देता है.

It is secreted by the pancreas.

[3 Marks] Trace the pathway of a nerve impulse through a reflex arc when you touch a hot plate. [3 Marks] Hot plate touch hone पर reflex arc के pathway को trace करें.

Answer:

Receptor (Skin of hand): Detects heat stimulus. Receptor (Skin): Heat stimulus detect करता है.
Sensory Neuron: Carries electrical impulse to spinal cord. Sensory Neuron: Impulse को spinal cord तक ले jata है.
Relay Neuron (Spinal Cord): Receives sensory signal and immediately transfers it to motor neuron. Relay Neuron (Spinal Cord): Signal integrate karke motor neuron तक transfer करता है.
Motor Neuron: Carries response impulse back to effector muscle. Motor Neuron: Response command signal wapas muscle तक ले jata है.
Effector (Bicep muscle): Muscle contracts, lifting the hand away from the hot plate. Effector (Bicep Muscle): Muscle contract hokar hand को hot plate से दूर pull करती है.

[5 Marks] List 5 endocrine glands, identify the hormone secreted by each, and state one key function for each. [5 Marks] 5 endocrine glands के name, उनके secreted hormones, और ek function की table बनाएं.

Answer:

Gland Gland (ग्रंथि)	Hormone Hormone (पादप हार्मोन)	Key Biological Function Key Biological Function (जैविक कार्य)
Pituitary Pituitary (पीयूष ग्रंथि)	Growth Hormone Growth Hormone (वृद्धि हार्मोन)	Regulates overall body growth and skeletal development. Body height, growth, और bones development coordinate करता है.
Thyroid Thyroid (अवटु ग्रंथि)	Thyroxine Thyroxine (थाइरॉक्सिन)	Controls metabolic rates of carbohydrate, protein, and fat. Fat, carbohydrates, और proteins के metabolism को control करता है.
Adrenal Adrenal (अधिवृक्क ग्रंथि)	Adrenaline Adrenaline (एड्रीनालिन)	Prepares muscles and organs for emergency fight-or-flight reactions. Emergency conditions में blood pressure, breathing, और alert system activate करता है.
Pancreas Pancreas (अग्न्याशय)	Insulin Insulin (इंसुलिन)	Lowers blood sugar levels by aiding cellular glucose transport. Blood stream से glucose extraction regulate karke sugar lower करता है.
Testes / Ovaries Testes / Ovaries (वृषण / अंडाशय)	Testosterone / Estrogen Testosterone / Estrogen (टेस्टोस्टेरोन / एस्ट्रोजन)	Coordinates development of secondary sexual characters during puberty. Puberty transition के dauran secondary sexual characteristics control करते हैं.

Sources:

NCERT Class 10 Science, Chapter 6: Control and Coordination, pp. 99–112. NCERT Class 10 Science, Chapter 6: Control and Coordination, pp. 99–112.
CBSE Board Secondary Curriculum Class 10 Science Guidelines. CBSE Board Secondary Curriculum Class 10 Science Guidelines.