A student accidentally touches a heated iron rod and immediately withdraws his hand. However, after a few seconds, he realizes the pain and says "It is very hot!"
Chapter 6 · CBSE Class X
📖 Introduction
📘 Definition
🏷️ Properties
Key Components of Control and Coordination
Properties
Stimulus
Any change in the environment (light, heat, touch, chemicals).
Receptors
Specialized cells/organs that detect stimuli (eyes, skin).
Control Centre
Brain or hormones that process information.
Effectors
Muscles or glands that produce a response.
Response
Action taken by the organism.
🔄 Process
Working Mechanism (Stepwise)
-
1Stimulus is detected by receptors.
-
2Information is transmitted to control centres (brain/spinal cord or hormones).
-
3Processing and decision-making occurs.
-
4Instructions are sent to effectors.
-
5Response is generated.
🗂️ Types / Category
Types of Control and Coordination
Animals
- Nervous System (fast, electrical signals)
- Endocrine System (slow, chemical hormones)
Plants
- Growth movements (tropisms)
- Hormonal control (auxins, gibberellins)
✏️ Example
1
Example
Daily Life)
Touching a hot object leads to immediate withdrawal of the hand. This is a reflex action controlled by the spinal cord.
2
Example
Example 2 (Plants)
A plant bends towards light. This is known as phototropism and is controlled by plant hormones.
3
Example
Concept-Based Question
Why do we blink when an object suddenly approaches our eyes?
Solution: It is a protective reflex action controlled by the nervous system to prevent injury.
🔢 Formula
Concept Flow (Stimulus-Response Pathway)
\[ \text{Stimulus} \rightarrow \text{Receptor} \rightarrow \text{Control Centre} \rightarrow \text{Effector} \rightarrow \text{Response} \]
🌟 Importance
⚡ Exam Tip
⚠️ Warning
Common Mistakes
📋 Case Study
Which part of the nervous system is responsible for immediate action?
Spinal cord controls the immediate reflex action.
Why is there a delay in feeling pain?
The brain processes the sensation of pain after receiving signals, hence the delay.
- Start with basic definitions and components.
- Understand nervous system and endocrine system separately.
- Study plant hormones and tropisms.
- Practice diagrams and NCERT questions.
- Revise with case-based and HOTS questions.
🧠 Introduction
The nervous system is a highly specialised communication and control network in animals that ensures
rapid coordination of body activities. It works through electrical impulses transmitted by nerve cells
(neurons), enabling organisms to respond quickly to environmental changes. This system is crucial for
survival, decision-making, reflexes, and voluntary actions.
📘 Definition
🗂️ Types / Category
Main Functions
Sensation
Detects internal and external stimuli using receptors.
Integration
Processes and interprets incoming signals in the brain/spinal cord.
Response
Sends commands to muscles or glands to act.
🎨 SVG Diagram
🔢 Formula
Working Mechanism
\[ \text{Stimulus} \rightarrow \text{Receptor} \rightarrow \text{Sensory Neuron} \rightarrow \text{CNS} \rightarrow \text{Motor Neuron} \rightarrow \text{Effector} \rightarrow \text{Response} \]
🗂️ Types / Category
Types of Nervous System
Central Nervous System (CNS)
The CNS acts as the body’s control center.
- Brain: Responsible for thinking, memory, emotions, intelligence, and voluntary actions.
- Spinal Cord: Carries nerve impulses between the brain and the rest of the body and controls reflex actions.
Peripheral Nervous System (PNS)
The PNS Connects CNS to the body
-
Cranial Nerves:
- 12 pairs arising from the brain.
- Control sensory functions (vision, smell, hearing), motor actions, and mixed functions. -
Spinal Nerves:
- 31 pairs arising from the spinal cord.
- Carry sensory and motor signals between CNS and body parts.
📌 Note
Neuron (Structural and Functional Unit)
📌 Note
Reflex Action and Reflex Arc
Reflex action is a quick, automatic, and involuntary response to a stimulus without conscious thinking.
Reflex Arc Pathway:
\[ \text{Stimulus} \rightarrow \text{Receptor} \rightarrow \text{Sensory Neuron} \rightarrow \text{Spinal Cord} \rightarrow \text{Motor Neuron} \rightarrow \text{Effector} \]
Example: Withdrawal of hand on touching a hot object.
1
Example
Withdrawal of hand on touching a hot object.
📌 Note
Link with Endocrine System
The nervous system works in coordination with the endocrine system for long-term regulation. While
nervous control is fast and short-lived, hormonal control is slow and long-lasting.
- Pituitary: Master gland that regulates other endocrine glands.
- Thyroid: Controls metabolism, growth, and development.
- Adrenal: Produces hormones involved in stress response and metabolism.
- Pancreas: Regulates blood glucose levels through insulin and glucagon.
- Hypothalamus: Connects the nervous and endocrine systems and controls the pituitary gland.
✏️ Example
Why do we withdraw our hand before feeling pain?
Because reflex action is controlled by the spinal cord, which acts faster than the brain.
🌟 Importance
⚡ Exam Tip
⚠️ Warning
Common Mistakes
📋 Case Study
A person touches a sharp object and quickly pulls back the hand. Later, the brain recognizes the pain.
- Which part acts first?
- Why is the brain involved later?
Answer:
- Spinal cord initiates reflex action.
- Brain processes pain sensation after receiving signals.
🗺️ Roadmap
- Understand neuron structure first
- Learn CNS and PNS differences
- Practice reflex arc diagrams
- Revise NCERT questions thoroughly
📖 Introduction
📘 Definition
🗂️ Types / Category
Types of Stimuli
External Stimuli
Stimuli from the external environment, such as light, heat, sound, touch, and chemicals.
Internal Stimuli
Stimuli arising within the body, such as hunger, thirst, hormonal changes, and pain.
📌 Note
Associated Components
- Receptor: Specialized cells or tissues that detect stimuli and convert them into nerve impulses.
- Effector: Muscles or glands that carry out the response after receiving signals.
- Response: The reaction or change in activity shown by the organism.
🔢 Formula
Stimulus–Response Pathway<
\[ \text{Stimulus} \rightarrow \text{Receptor} \rightarrow \text{Sensory Neuron} \rightarrow \text{CNS} \rightarrow \text{Motor Neuron} \rightarrow \text{Effector} \rightarrow \text{Response} \]
✏️ Example
1
Example
Touching a hot object (stimulus) → receptors in skin detect heat → hand withdraws (response).
Eample
Bright light falling on eyes → pupils contract to protect retina.
Why do we feel hungry after a long time without food?
Hunger is an internal stimulus triggered by changes in glucose level in the body.
🗒️ Important
- Initiates all control and coordination processes
- Helps organisms survive by responding to environmental changes
- Maintains internal balance (homeostasis)
- Essential for reflex and voluntary actions
⚡ Exam Tip
⚠️ Warning
Common Mistakes
📋 Case Study
A person suddenly withdraws their hand after touching a hot pan, and later realizes the pain.
- Identify the stimulus and response.
- Which organ detects the stimulus?
Answer:
- Stimulus: Heat from the pan; Response: Withdrawal of hand
- Receptors in the skin detect the stimulus
🗺️ Roadmap
Study Roadmap
- Start with definition and types of stimuli
- Understand receptor-effector mechanism
- Practice diagrams and pathways
- Revise examples for application-based questions
📖 Introduction
📘 Definition
🖼️ Figure
Structure of Neuron
(a) Structure of neuron (b) Neuromuscular junction
🗂️ Types / Category
Parts of Neuron
- Cell Body (Cyton) Contains nucleus and organelles like mitochondria, Golgi apparatus, and endoplasmic reticulum; responsible for metabolic activities.
- Dendrites Short, branched projections that receive signals from other neurons or receptors.
- Axon Long, cylindrical structure that conducts nerve impulses away from the cell body
- Myelin Sheath (if present) Insulating layer that increases speed of impulse transmission.
- Axon Terminals End branches that release neurotransmitters to pass signals to the next cell.
🧠 Functioning Of Neuron
\[ \text{Dendrite} \rightarrow \text{Cell Body} \rightarrow \text{Axon} \rightarrow \text{Axon Terminal} \rightarrow \text{Next Neuron/Muscle} \]
Electrical impulses travel in one direction only. At synapses (junctions between neurons), the signal is transmitted chemically using neurotransmitters.
🗂️ Types / Category
Types of Neurons
Sensory Neurons
Carry nerve impulses from receptors to the central nervous system (CNS).
Sensory neurons transmit signals from sense organs such as the eyes, skin, nose, tongue, and ears to the brain or spinal cord. They help detect stimuli like light, heat, pain, pressure, sound, and chemicals.
Sensory neurons transmit signals from sense organs such as the eyes, skin, nose, tongue, and ears to the brain or spinal cord. They help detect stimuli like light, heat, pain, pressure, sound, and chemicals.
Motor Neurons
Carry nerve impulses from the CNS to effectors such as muscles and glands.
Motor neurons transmit commands from the brain or spinal cord to muscles or glands, producing actions such as movement, secretion, or other responses.
Motor neurons transmit commands from the brain or spinal cord to muscles or glands, producing actions such as movement, secretion, or other responses.
Interneurons
Connect sensory and motor neurons within the CNS and help in processing information.
Interneurons are found entirely within the central nervous system. They link sensory and motor neurons, process incoming information, and help in decision-making and coordination.
Interneurons are found entirely within the central nervous system. They link sensory and motor neurons, process incoming information, and help in decision-making and coordination.
📌 Note
Structure of Motor Neuron
- Multipolar in structure (one axon, multiple dendrites)
- Cell body (soma) contains nucleus
- Axon carries impulses away from CNS
- Dendrites receive signals from other neurons
Types of Motor Neurons
Upper Motor Neurons
Located in the brain, these neurons carry motor commands from the cerebral cortex to the spinal cord. They play an important role in planning, initiating, and controlling voluntary movements.
Lower Motor Neurons
Located in the spinal cord and brainstem, these neurons carry impulses from the CNS to skeletal muscles. They directly stimulate muscle contraction and produce movement.
📌 Note
Functions of Neurons
🔎 Key Fact
Neurogenesis
📌 Note
Synapse
✏️ Example
1
Example
When you touch a hot object, sensory neurons carry the signal to the spinal cord, and motor neurons
send instructions to muscles to withdraw the hand.
Why is impulse transmission faster in myelinated neurons?
Because the myelin sheath allows impulses to jump between nodes (saltatory conduction), increasing speed.
🗒️ Important
- Enables rapid communication within the body
- Controls reflex and voluntary actions
- Essential for thinking, learning, and memory
- Maintains coordination and balance
⚡ Exam Tip
⚡ Exam Tip
Common Mistakes
📋 Case Study
p>
A person suffers damage to the myelin sheath of neurons. As a result, nerve impulse transmission slows down.
- Explain why impulse transmission is affected.
- Which property of neurons is lost?
Answer:
- Myelin sheath enables fast conduction; its damage slows impulse transmission.
- Insulation and rapid conduction property is lost.
🗺️ Roadmap
- Start with neuron structure and diagram
- Understand impulse transmission mechanism
- Learn types of neurons
- Practice NCERT diagrams and questions
📖 Introduction
📘 Definition
💡 Concept
Reflex Arc
🧠 Remember
Reflex Arc Pathway
\[ \text{Stimulus} \rightarrow \text{Receptor} \rightarrow \text{Sensory Neuron} \rightarrow \text{Spinal Cord} \rightarrow \text{Motor Neuron} \rightarrow \text{Effector} \rightarrow \text{Response} \]
🗂️ Types / Category
Components of Reflex Arc
Receptor
Detects a stimulus, such as heat, pain, touch, or pressure, and converts it into a nerve impulse.
Sensory Neuron
Carries the nerve impulse from the receptor to the spinal cord through the dorsal root.
Interneuron
Found in the spinal cord, it receives the sensory impulse, processes it quickly, and passes the signal to the motor neuron.
Motor Neuron
Carries the impulse from the spinal cord to the effector, such as a muscle or gland, through the ventral root.
Effector
The muscle or gland that carries out the response, such as withdrawing a hand from a hot object or secreting a substance.
✏️ Example
1
Example
Withdrawal of hand when touching a hot object.
2
Example
Blinking of eyes when dust enters.
Why are reflex actions faster than voluntary actions?
Because reflex actions bypass the brain initially and are controlled by the spinal cord.
🗂️ Types / Category
Types of Reflex Actions
Natural Reflexes
Inborn, automatic responses present from birth. These reflexes do not need learning or practice and help protect the body or maintain basic functions, such as blinking, coughing, sneezing, and withdrawing the hand from a hot object.
Conditioned Reflexes
Learned or acquired responses developed through experience, training, or repeated association. These reflexes are not present at birth and can change over time, such as salivation at the smell of food or braking a bicycle automatically after practice.
🌟 Importance
⚡ Exam Tip
⚠️ Warning
Common Mistakes
📋 Case Study
A person steps on a sharp object and immediately lifts the foot before realizing the pain.
- Which part of the nervous system controls this action?
- Why is the brain involved later?
Answer:
- Spinal cord controls the reflex action.
- Brain processes the sensation after receiving signals.
📽️ Animation
Reflex Arc - Animation
Visualization of impulse flow during reflex action.
🗺️ Roadmap
Study Roadmap
- Understand reflex arc components
- Memorize pathway sequence
- Practice diagrams
- Solve NCERT and case-based questions
📘 Definition
📌 Note
Parts of Brain
Fore Brain
Mid Brain
Hind Brain
The brain is divided into three major regions: forebrain, midbrain, and hindbrain.
Each region performs specific functions but works in coordination with others.
Forebrain
- Cerebrum: Largest part of the brain responsible for voluntary actions, intelligence, memory, reasoning, speech, emotions, and sensory perception.
- Thalamus: Acts as a relay centre, directing sensory impulses to appropriate regions of cerebrum.
- Hypothalamus: Maintains homeostasis by regulating hunger, thirst, body temperature, and sleep; also links nervous system with endocrine system.
Midbrain
- Controls reflex movements of head, neck, and eyes.
- Processes visual and auditory information.
- Plays a role in motor coordination.
Hindbrain
- Cerebellum: Maintains balance, posture, and coordination of muscular activities (e.g., walking, cycling).
- Pons: Regulates breathing cycle and sleep; acts as a bridge between different parts of the brain.
- Medulla Oblongata: Controls involuntary actions such as heartbeat, blood pressure, breathing, salivation, and vomiting.
✏️ Example
1
Example
Solving a mathematical problem involves cerebrum for thinking and reasoning.
2
Example
Maintaining balance while riding a bicycle is controlled by cerebellum.
Why does damage to the medulla oblongata become life-threatening?
Because it controls vital involuntary functions like breathing and heartbeat.
🌟 Importance
⚡ Exam Tip
⚠️ Warning
Common Mistakes
📋 Case Study
A person loses balance while walking and has difficulty maintaining posture.
- Which part of the brain is affected?
- What function is impaired?
Answer:
- Cerebellum is affected.
- Balance and coordination are impaired.
🗺️ Roadmap
Study Roadmap
- Understand division of brain
- Learn functions of each part
- Practice diagrams
- Revise NCERT questions thoroughly
📘 Definition
💡 Concept
Key Concept
🗂️ Types / Category
Tropic Movements
Nastic Movements
Types of Plant Movements
Tropic Movements
- Growth-dependent movements
- Directional response with respect to stimulus
- Permanent and irreversible
- Found in all plants
- Slow response
Nastic Movements
- Growth-independent movements
- Non-directional response
- Temporary and reversible
- Found in specialized plants (e.g., Mimosa pudica)
- Quick response
📊 Comparison Table
Tropic vs Nastic Movements
| Feature | Tropic Movement | Nastic Movement |
|---|---|---|
| Dependence on Growth | Growth-dependent | Growth-independent |
| Direction | Directional | Non-directional |
| Speed | Slow | Fast |
| Reversibility | Irreversible | Reversible |
📊 Comparison Table
Tropic Movements
Types of Tropic Movements
| Type | Stimulus Response | Example |
|---|---|---|
| Phototropism | Towards/away from light | Shoot bends towards light |
| Geotropism (Gravitropism) | Towards/away from gravity | Roots grow downward |
| Hydrotropism | Towards water | Roots grow towards moisture |
| Chemotropism | Towards chemicals | Pollen tube grows towards ovule |
| Thigmotropism | Response to touch | Tendrils coil around support |
🗂️ Types / Category
Auxin
Gibberellins
Cytokinins
Abscisic Acid
Ethylene
Plant Hormones (Phytohormones)
Plant Growth Promoters
Auxin
- Promotes cell elongation in shoots and young stems.
- Controls phototropism and gravitropism.
- Helps in root initiation and fruit development.
- Prevents premature falling of leaves and fruits in some plants.
- Stimulate stem elongation and overall plant growth.
- Promote seed germination by breaking dormancy.
- Enhance flowering and fruit growth.
- Help in bolting and overcoming dwarfism in plants.
- Promote cell division and growth.
- Delay ageing (senescence) of leaves and flowers.
- Promote lateral bud growth and shoot formation.
- Work together with auxins to regulate plant development.
Plant Growth Inhibitors
Abscisic Acid (ABA)
- Induces stomatal closure during water stress.
- Maintains dormancy in seeds and buds.
- Slows down growth under unfavorable conditions.
- Helps plants survive drought and other stress conditions.
- Promotes fruit ripening.
- Causes leaf, flower, and fruit fall.
- Involved in ageing processes.
- Helps in response to mechanical stress and senescence.
✏️ Example
1
Example
Sunflower turning towards sunlight due to phototropism.
2
Example
Mimosa pudica folding leaves on touch (thigmonasty).
Why do roots grow downward even when a plant is placed horizontally?
Due to positive geotropism (response to gravity).
🌟 Importance
⚡ Exam Tip
⚠️ Warning
Common Mistakes
📋 Case Study
A plant kept in a dark room bends towards a small window through which light enters.
- Identify the type of movement.
- Which hormone is responsible?
Answer:
- Phototropism
- Auxin
🗺️ Roadmap
Study Roadmap
- Understand plant movement types
- Learn all tropisms with examples
- Memorize hormones and functions
- Practice NCERT and case-based questions
📘 Definition
💡 Concept
Key Concept
🗂️ Types / Category
Steroid
Peptide
Types of Animal Hormones
Steroid Hormones
Derived from cholesterol; lipid-soluble hormones that easily pass through cell membranes and bind to intracellular receptors. They usually act by regulating gene expression and produce long-lasting effects.
Examples: Testosterone, Estrogen, Progesterone, Cortisol, Aldosterone
Examples: Testosterone, Estrogen, Progesterone, Cortisol, Aldosterone
Peptide Hormones
Made of short or long chains of amino acids; water-soluble hormones that cannot pass through the cell membrane easily and therefore act through cell surface receptors. They usually trigger second messenger systems and produce rapid effects.
Examples: Insulin, Growth Hormone (GH), Thyroid-Stimulating Hormone (TSH), ADH, Oxytocin
Examples: Insulin, Growth Hormone (GH), Thyroid-Stimulating Hormone (TSH), ADH, Oxytocin
🗂️ Types / Category
Insulin
Adrenaline
Thyroxine
Antidiuretic
Oxytocin
Important Hormones and Functions
Insulin
A hormone secreted by the pancreas that lowers blood glucose levels by promoting glucose uptake by cells and conversion of glucose into glycogen.
Adrenaline (Epinephrine)
A stress hormone released by the adrenal glands that prepares the body for emergency situations by increasing heart rate, blood pressure, and energy availability.
Growth Hormone
Secreted by the pituitary gland; it promotes the growth of bones, muscles, and other body tissues.
Thyroxine (Thyroid Hormone)
Secreted by the thyroid gland; it regulates metabolism, supports growth, and helps maintain normal body activity.
Antidiuretic Hormone (ADH)
Helps maintain water balance by reducing water loss through the kidneys and conserving body fluid.
Oxytocin
Stimulates uterine contractions during childbirth and triggers milk release from the mammary glands.
Cortisol
A hormone of the adrenal cortex that helps regulate metabolism, blood sugar, and the body’s response to stress.
🗂️ Types / Category
Pituitary
Thyroid
Adrenal
Pancreas
Testes/Ovaries
Major Endocrine Glands
Pituitary Gland
Known as the master gland, it controls many other endocrine glands by releasing hormones that regulate growth, reproduction, and metabolism. It secretes hormones such as growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), prolactin, FSH, LH, and also stores and releases oxytocin and ADH.
Thyroid Gland
A butterfly-shaped gland in the neck that controls metabolic rate, energy use, heart rate, and growth. It produces thyroxine (T4) and triiodothyronine (T3), and also secretes calcitonin, which helps regulate calcium levels in the blood.
Adrenal Glands
Located on top of the kidneys, these glands produce hormones that help the body respond to stress and maintain salt and sugar balance. The adrenal medulla secretes adrenaline and noradrenaline, while the adrenal cortex secretes cortisol, aldosterone, and small amounts of sex hormones.
Pancreas
A mixed gland that functions as both an endocrine and exocrine gland. Its endocrine part, the islets of Langerhans, produces insulin and glucagon to regulate blood glucose levels and maintain energy balance.
Testes/Ovaries
The reproductive glands that produce sex hormones and also generate gametes. Testes secrete testosterone, while ovaries secrete estrogen and progesterone; these hormones control sexual development, reproductive functions, and secondary sexual characteristics.
✏️ Example
1
Example
After eating food, insulin is released to lower blood glucose levels.
2
Example
During danger, adrenaline increases heart rate and breathing.
Why is hormonal control slower than nervous control?
Because hormones travel through blood, which takes more time than nerve impulses.
🌟 Importance
⚡ Exam Tip
⚠️ Warning
Common Mistakes
📋 Case Study
A person shows symptoms of high blood sugar levels and fatigue.
- Which hormone is likely deficient?
- Which gland produces it?
Answer:
- Insulin
- Pancreas
🗺️ Roadmap
Study Roadmap
- Understand types of hormones
- Learn major glands and functions
- Revise examples like insulin and adrenaline
- Practice NCERT and case-based questions
Control & Coordination
NCERT Science · Class X · Chapter 6
AI Learning Engine
Chapter 6 — Control & Coordination
A complete AI-powered study engine covering nervous system, hormones, reflex arcs, and plant coordination.
11
Core Concepts
8
Formulas & Terms
20
Practice Questions
5
Interactive Modules
🧬 What You'll Learn
Nervous System
Neurons & Synapses
Reflex Arc
Human Brain
Endocrine System
Plant Hormones
Tropic Movements
🎯 Chapter Flow
Control & Coordination
↓
In Animals → Nervous System
↓
In Animals → Endocrine System
↓
In Plants → Phytohormones & Movements
🧭 How To Use This Engine
📖
Read Concepts
Deep, exam-ready explanations with examples.
🔬
Use AI Solver
Step-by-step solutions to concept problems.
🎯
Test Yourself
Quiz, matching, fill-in-blanks & concept maps.
Core Concepts
Organised concept-by-concept explanations with examples, mechanisms, and exam insights.
⚡ 1. Why Do We Need Control & Coordination?
All living organisms need to respond to changes in their environment — these changes are called stimuli. The response involves cells, tissues, and organs working together in a coordinated manner.
Key Idea: In multicellular organisms, specialised tissues (nervous & endocrine) perform control and coordination. In plants, coordination happens through chemical signals without a nervous system.
🔌 2. The Neuron — Structural & Functional Unit of Nervous System
A neuron (nerve cell) is the basic unit of the nervous system. It receives and transmits electrical impulses.
Parts of a Neuron
- →Cell body (Cyton/Soma): Contains nucleus and cytoplasm; metabolic centre.
- →Dendrites: Short, branched projections that receive signals from other neurons.
- →Axon: Long fibre that conducts impulses away from cell body. Ends in axon terminals.
- →Myelin sheath: Insulating covering of the axon, speeds up impulse transmission.
Synapse
The junction between two neurons is called a synapse. Electrical impulses cannot cross this gap directly.
Electrical impulse → pre-synaptic terminal
↓
Neurotransmitters released into synaptic cleft
↓
Received by dendrites of next neuron
⚡ 3. Reflex Action & Reflex Arc
A reflex action is a sudden, involuntary response to a stimulus that does not involve the conscious brain. It is a protective mechanism. The pathway is called the reflex arc.
Path of a Reflex Arc
Stimulus (receptor)
→
Sensory neuron
→
Spinal cord (relay neuron)
→
Motor neuron
→
Effector (muscle/gland)
Exam Insight: Reflex arcs pass through the spinal cord, not the brain. The brain becomes aware of the reflex only after it has occurred. Example: Pulling hand away from hot object.
🧩 4. The Human Brain — Structure & Function
| Region | Parts | Key Functions |
|---|---|---|
| Forebrain (Prosencephalon) | Cerebrum, Hypothalamus | Thinking, reasoning, memory, voluntary movements, smell, sight; regulates hunger, thirst, temperature |
| Midbrain (Mesencephalon) | Tectum, Tegmentum | Relay of visual & auditory information; eye movement control |
| Hindbrain (Rhombencephalon) | Cerebellum, Pons, Medulla | Cerebellum: balance, posture, precision movement; Pons: respiration regulation; Medulla: involuntary actions (heartbeat, breathing) |
Memory Hook: "Cerebrum thinks, Cerebellum coordinates, Medulla survives." These three functions map perfectly to the three major brain regions.
🔗 5. Central vs Peripheral Nervous System
| Feature | CNS | PNS |
|---|---|---|
| Includes | Brain + Spinal cord | All nerves outside brain & spinal cord |
| Role | Processing centre; integration | Carry signals to/from CNS |
| Divisions | — | Somatic NS + Autonomic NS |
| Autonomic division | — | Sympathetic (fight/flight) + Parasympathetic (rest/digest) |
🧪 6. Endocrine System — Chemical Coordination
The endocrine system uses hormones — chemical messengers secreted by ductless glands directly into the bloodstream — to regulate body functions. This is slower but longer-lasting than nervous coordination.
| Gland | Hormone(s) | Target / Function |
|---|---|---|
| Hypothalamus | Releasing / Inhibiting hormones | Controls pituitary gland secretions |
| Pituitary (Master gland) | GH, TSH, FSH, LH, ADH, Oxytocin | Growth; controls other endocrine glands; water reabsorption; uterine contraction |
| Thyroid | Thyroxine (T₄), T₃ | Metabolic rate; growth; development (requires iodine) |
| Parathyroid | PTH (Parathormone) | Calcium & phosphate balance in blood |
| Adrenal (cortex) | Cortisol, Aldosterone | Stress response; Na⁺/K⁺ balance |
| Adrenal (medulla) | Adrenaline (Epinephrine) | Emergency hormone: heart rate ↑, blood flow to muscles ↑, breathing ↑, digestion ↓ |
| Pancreas (Islets of Langerhans) | Insulin (β cells), Glucagon (α cells) | Insulin: blood sugar ↓; Glucagon: blood sugar ↑ |
| Gonads (Testes) | Testosterone | Male secondary sexual characteristics; sperm production |
| Gonads (Ovaries) | Oestrogen, Progesterone | Female secondary sexual characteristics; menstrual cycle; pregnancy |
| Pineal | Melatonin | Sleep-wake cycle (circadian rhythm) |
| Thymus | Thymosin | Immunity — maturation of T-lymphocytes |
🌿 7. Coordination in Plants
Plants have no nervous system. They coordinate using phytohormones (plant hormones) and show movements in response to stimuli.
| Hormone | Site of Production | Key Effects |
|---|---|---|
| Auxin (IAA) | Shoot tips (apical meristem) | Cell elongation (one side); phototropism; apical dominance; delays abscission |
| Gibberellin (GA) | Seeds, roots, young leaves | Stem elongation; seed germination; fruit development without fertilisation (parthenocarpy) |
| Cytokinin | Roots, developing fruits/seeds | Cell division; delays senescence (ageing); promotes lateral bud growth |
| Abscisic Acid (ABA) | Leaves, seeds, roots | Stress hormone; stomata closure; seed dormancy; inhibits growth — "stress hormone" |
| Ethylene | Ripening fruits, nodes | Fruit ripening; leaf fall; horizontal growth; senescence |
🌻 8. Tropic Movements in Plants
Tropic (tropistic) movements are directional growth movements in plants in response to directional stimuli. They are caused by differential cell elongation due to unequal distribution of auxin.
| Type | Stimulus | Example | Organ Response |
|---|---|---|---|
| Phototropism | Light | Shoot bending toward light | Shoot: +ve; Root: −ve |
| Geotropism | Gravity | Root grows downward | Root: +ve; Shoot: −ve |
| Hydrotropism | Water | Root bends toward water | Root: +ve |
| Thigmotropism | Touch | Tendrils coiling around support | Tendrils: +ve |
| Chemotropism | Chemical | Pollen tube grows toward ovule | +ve toward chemical |
Mechanism of Phototropism: Light causes auxin to migrate from the illuminated side to the shaded side of the shoot. Higher auxin concentration → greater elongation on shaded side → shoot bends toward light.
🌙 9. Nastic Movements
Nastic movements are non-directional plant responses (direction does not depend on stimulus direction). They occur due to changes in turgor pressure, not cell growth.
Seismonasty (Touch)
Mimosa pudica (touch-me-not) folds its leaves on touch. Caused by rapid loss of water from pulvinus cells → turgor decreases → leaflets fold.
Photonasty (Light)
Opening and closing of flowers in response to light intensity (e.g., dandelion opens in sunlight, closes at night). Due to differential turgor in petals.
⚖️ 10. Nervous vs Hormonal Coordination
| Feature | Nervous System | Endocrine System |
|---|---|---|
| Speed | Very fast (milliseconds) | Slow (seconds to days) |
| Messenger | Electrical impulse + neurotransmitter | Hormones (chemical) |
| Medium | Neurons | Blood |
| Effect duration | Brief | Long-lasting |
| Specificity | Very specific pathway | Targets specific cells via receptors |
| Memory | Can form memory | No memory formation |
🔑 11. Feedback Mechanisms
Hormone secretion is regulated by negative feedback: when hormone level rises to normal, the signal for its secretion is inhibited.
Negative Feedback (Example: Thyroxine)
Low blood thyroxine → Hypothalamus releases TRH → Pituitary releases TSH → Thyroid secretes Thyroxine → High thyroxine → Inhibits TRH & TSH release
Also Know: Insulin-glucagon feedback for blood glucose is a classic negative feedback loop. Insulin released when glucose ↑; glucagon released when glucose ↓. Together they maintain homeostasis.
Key Terms & Concepts
Precise scientific definitions, relationships, and conceptual formulas for quick revision.
📐 Important Relationships
Synapse Signal Transfer
Electrical Impulse → Neurotransmitter (chemical) → Electrical ImpulseReflex Arc Direction
Receptor → Sensory Neuron → CNS (Spinal Cord) → Motor Neuron → EffectorHormone Action Principle
Stimulus → Endocrine Gland → Hormone (via blood) → Target Organ → ResponsePhototropism (Auxin)
Light → Auxin migrates away → [Illuminated side: less auxin] → [Shaded side: more auxin] → Differential growth → Bending toward light📚 Must-Know Definitions
SYNAPSE
The functional junction between two neurons; site of neurotransmitter release; ensures one-directional signal flow.
HORMONE
A chemical substance produced by an endocrine gland, secreted directly into the blood, and acting on distant target organs in minute quantities.
TROPIC MOVEMENT
Directional growth movement of a plant part toward or away from a stimulus. +ve = toward; −ve = away.
HOMEOSTASIS
Maintenance of a constant internal environment in the body despite external changes (e.g., blood glucose, temperature, pH).
🧠 Quick Comparison Formulas
Iodine & Thyroxine
Deficiency of Iodine → Less Thyroxine → Goitre (enlargement of thyroid gland)Insulin Deficiency
Less Insulin → High blood glucose → Diabetes mellitus (Type 1)Growth Hormone
Excess GH (childhood) → Gigantism | Deficiency GH → Dwarfism🔬 Neuron Signal Mnemonics
DAME for Brain Parts: Diencephalon, Allocortex, Medulla, Encephalon — structural layers of the brain.
AGACE for Plant Hormones: Auxin, Gibberellin, Abscisic acid, Cytokinin, Ethylene — the five main phytohormones.
Signal Speeds: Nervous system = electrical (very fast, milliseconds) | Hormonal = chemical via blood (slow, seconds to hours).
Pituitary = Master gland because it secretes tropic hormones (TSH, FSH, LH, ACTH) that control other endocrine glands.
Step-by-Step AI Solver
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Concept Questions
Rich, concept-building questions with full step-by-step solutions — organised by concept, no textbook repetition.
Neurons
Brain
Reflex
Hormones
Plants
Comparisons
🔌
Neurons & Synapses
Why must neurotransmitters be released at a synapse rather than allowing the electrical impulse to jump directly?
▼
Step-by-Step Solution
-
1The synaptic cleft is a fluid-filled gap — electricity cannot travel across a fluid medium efficiently.
-
2Neurotransmitters allow for signal modulation — the receiving neuron can decide whether to fire based on the combined input from many synapses (summation).
-
3This ensures one-directional transmission: neurotransmitters are only stored in the pre-synaptic terminal, preventing backward signals.
-
4It also allows for pharmacological control — drugs can block or mimic neurotransmitters, enabling treatment of neurological conditions.
🔌
Neurons & Synapses
A student says 'neurons are like wires in a circuit.' Evaluate this analogy — what is correct and what is misleading?
▼
Step-by-Step Solution
-
1Correct: Both carry electrical signals; both have a specific direction of current flow; both connect components in the body/circuit.
-
2Misleading: Neurons are NOT passive conductors. The signal is an electrochemical impulse (action potential), not a simple electrical current.
-
3Misleading: Signal strength does NOT decrease with distance in neurons (unlike wire resistance). The signal is regenerated at each node of Ranvier.
-
4Misleading: Neurons can integrate multiple signals (summation), 'think' partially, and adapt — wires cannot.
🧩
Brain Structure
Why does damage to the medulla oblongata result in death, while damage to the cerebrum may not?
▼
Step-by-Step Solution
-
1The medulla oblongata controls all vital involuntary functions: cardiac rhythm, respiratory rate, blood pressure, and swallowing.
-
2These functions are non-negotiable for survival — stopping them even briefly causes death.
-
3The cerebrum controls voluntary actions, thinking, and memory. These can be compensated for partially (unconscious reflex activity continues).
-
4Conclusion: Medulla damage = loss of life-maintaining functions. Cerebrum damage = loss of higher cognitive functions, but survival is possible with medical support.
⚡
Reflex Arc
Design an experiment to prove that the spinal cord, not the brain, is the centre of reflex action.
▼
Step-by-Step Solution
-
1Hypothesis: Reflex actions are processed in the spinal cord independently of the brain.
-
2Procedure: Use an animal model (frog). Destroy the brain (pith the frog) while keeping the spinal cord intact.
-
3Observation: When the leg is pinched, the frog still withdraws its leg reflexively.
-
4Conclusion: Since the brain is absent yet reflex occurs, the spinal cord alone is sufficient for reflex action.
-
5Extension: Now sever the spinal cord and repeat — the reflex disappears, confirming the spinal cord's role.
🧪
Endocrine System
Explain why the same hormone (adrenaline) can have different effects on different organs.
▼
Step-by-Step Solution
-
1Adrenaline binds to specific receptors on target cells. Different organs have different receptor subtypes (α and β adrenergic receptors).
-
2Heart: β1 receptors → increased heart rate and force of contraction.
-
3Bronchi: β2 receptors → dilation of airways (more oxygen intake).
-
4Digestive system: Mainly α receptors → decreased blood flow, slowed peristalsis.
-
5Key Principle: It is not the hormone alone, but the receptor type on the target cell that determines the response. Same hormone, different lock → different effect.
🧪
Endocrine System
Why are endocrine glands called 'ductless glands'? What advantage does this give over exocrine glands?
▼
Step-by-Step Solution
-
1Endocrine glands lack ducts (tubes). They secrete hormones directly into the surrounding capillaries → bloodstream.
-
2Exocrine glands (e.g., sweat, salivary) use ducts to deliver secretions to specific surfaces.
-
3Advantage 1: Blood acts as a universal carrier → hormones can reach any organ in the body, not just nearby tissues.
-
4Advantage 2: Enables systemic (whole-body) coordination from a single gland.
-
5Advantage 3: Enables rapid concentration adjustment through feedback mechanisms.
🌿
Plant Hormones
A plant is kept in a dark room except for light coming from one window. Describe and explain what happens to the shoot over 5 days.
▼
Step-by-Step Solution
-
1Day 1–2: Light enters from one direction. Auxin (produced at shoot tip) begins migrating to the shaded side.
-
2Day 2–3: Shaded side has higher auxin concentration → cells on shaded side elongate faster than illuminated side.
-
3Day 4–5: The shoot visibly bends toward the light source (positive phototropism).
-
4Mechanism: Differential growth (not turgor change) due to auxin gradient is the cause.
-
5If shoot tip is removed: No auxin produced → no bending, regardless of light direction (confirms auxin's role).
🌻
Plant Movements
Tendrils coil around a support (thigmotropism) but Mimosa pudica folds its leaves on touch (seismonasty). Why are these classified differently?
▼
Step-by-Step Solution
-
1Thigmotropism (tendrils): Movement direction DEPENDS on the direction of touch. The tendril wraps toward the support = directional. Caused by differential growth (auxin-driven cell elongation). Irreversible.
-
2Seismonasty (Mimosa): Movement direction does NOT depend on where the stimulus comes from. Leaves fold regardless of touch direction. Caused by rapid change in turgor pressure in pulvinus cells (water flows out). Reversible in minutes.
-
3Classification rule: Tropic = directional growth. Nastic = non-directional turgor change.
⚖️
Comparison
Compare the speed of response in nervous and hormonal systems. Give real-life examples where each speed is advantageous.
▼
Step-by-Step Solution
-
1Nervous system: Signal travels at up to 100 m/s via electrical impulses. Response in milliseconds.
-
2Advantage: Essential when speed is critical. Example: Jerking hand away from fire, blinking when something approaches the eye, catching a falling object.
-
3Hormonal system: Hormones travel via blood. Response in seconds to hours.
-
4Advantage: For sustained, long-term changes. Example: Puberty changes (months), menstrual cycle regulation (days), growth (years), stress adaptation (hours).
-
5Conclusion: Nervous = fast but brief. Hormonal = slow but sustained. Both work together for complete coordination.
⚖️
Comparison
Construct an argument: Is the hypothalamus the true 'master gland' rather than the pituitary?
▼
Step-by-Step Solution
-
1Argument FOR hypothalamus as master: The hypothalamus controls the pituitary by releasing releasing-hormones and inhibiting-hormones (TRH, GnRH, etc.).
-
2Without hypothalamus signals, the pituitary cannot secrete its tropic hormones (TSH, FSH, LH, GH, etc.).
-
3The hypothalamus also connects the nervous and endocrine systems — it receives signals from the brain and translates them into hormonal responses.
-
4Counter-argument: The pituitary physically governs 7+ endocrine glands simultaneously and is often the point of pathology (e.g., pituitary tumours cause gigantism/Cushing's).
-
5Conclusion: The hypothalamus–pituitary axis is a hierarchy. Hypothalamus = supreme commander; pituitary = field commander. Neither operates independently.
Tips, Tricks & Common Mistakes
Curated exam-level tips and frequent errors students make in Chapter 6.
✅ Tricks & Tips
Tropic direction memory: Shoots are POSITIVE phototropic & NEGATIVE geotropic. Roots are the OPPOSITE. Think: shoots chase light, roots avoid it and chase gravity.
Hormone acronym — AGACE: Auxin (growth), Gibberellin (elongation), Abscisic acid (stress/inhibition), Cytokinin (division), Ethylene (ripening/senescence).
Brain regions: Cerebrum = C for 'Cognition'. Cerebellum = second C for 'Coordination'. Medulla = M for 'Mandatory survival'. Never mix them up in diagrams.
Reflex arc vs voluntary: In a reflex, the response occurs BEFORE the brain is even aware. You feel pain after you've already pulled your hand away.
Iodine question: If asked why seafood prevents goitre — seafood is rich in iodine → sufficient thyroxine → no goitre. Always connect the nutrient → hormone → disease chain.
Pancreas is BOTH exocrine and endocrine: Exocrine = digestive enzymes via pancreatic duct. Endocrine = insulin & glucagon via blood. This dual role is a very common exam question.
❌ Common Mistakes to Avoid
Mistake: "Reflex actions are processed in the brain."
Correct: Reflex arcs are completed at the spinal cord level. The brain gets the signal AFTER the response. (Except cranial reflexes like blinking, which use brainstem.)
Correct: Reflex arcs are completed at the spinal cord level. The brain gets the signal AFTER the response. (Except cranial reflexes like blinking, which use brainstem.)
Mistake: "Auxin causes bending toward light because it increases on the illuminated side."
Correct: Auxin migrates to the SHADED side. More auxin → more elongation on shaded side → bending TOWARD light (not away from auxin).
Correct: Auxin migrates to the SHADED side. More auxin → more elongation on shaded side → bending TOWARD light (not away from auxin).
Mistake: Confusing nastic and tropic movements.
Correct: Tropic = directional (growth-based). Nastic = non-directional (turgor-based). Mimosa is NASTIC, not tropic.
Correct: Tropic = directional (growth-based). Nastic = non-directional (turgor-based). Mimosa is NASTIC, not tropic.
Mistake: "Pituitary is the master gland and works independently."
Correct: Pituitary is controlled by the hypothalamus through releasing and inhibiting hormones. It is NOT fully independent.
Correct: Pituitary is controlled by the hypothalamus through releasing and inhibiting hormones. It is NOT fully independent.
Mistake: "Hormones act on all cells."
Correct: Hormones only act on specific TARGET cells/organs that have the matching receptor proteins. A hormone without a receptor = no effect.
Correct: Hormones only act on specific TARGET cells/organs that have the matching receptor proteins. A hormone without a receptor = no effect.
Mistake: "Plants have no response system since they lack a nervous system."
Correct: Plants respond using phytohormones and show both tropic (growth-based) and nastic (turgor-based) movements. They are highly responsive to their environment.
Correct: Plants respond using phytohormones and show both tropic (growth-based) and nastic (turgor-based) movements. They are highly responsive to their environment.
Mistake: Mixing Dendrites and Axons.
Correct: Dendrites → receive signals (toward cell body). Axon → sends signals away from cell body. Memory: Dendrites = 'D for 'Deliver to'; Axon = 'A for Away'.
Correct: Dendrites → receive signals (toward cell body). Axon → sends signals away from cell body. Memory: Dendrites = 'D for 'Deliver to'; Axon = 'A for Away'.
MCQ Quiz
15 carefully crafted questions. Instant feedback with explanation for every answer.
Question 1 of 15
Match It
Click a term on the left, then its matching description on the right. Match all 8 pairs!
Score: 0 / 8 matched
Fill in the Blanks
Complete each sentence with the correct scientific term. Press Check to verify.
Interactive Diagrams
Annotated SVG diagrams of key structures. Click labels to reveal information.
🔌 Structure of a Neuron
Impulse direction: Dendrites → Cell Body → Axon → Axon Terminals → Synapse. The myelin sheath speeds up transmission by saltatory conduction (jumping between nodes of Ranvier).
⚡ Reflex Arc Pathway
The dashed line shows that the brain receives information about the reflex, but the action is complete before the brain can respond. This is why reflex arcs are faster than voluntary actions.
🧪 Major Endocrine Glands — Human Body
🧠
Hypothalamus
Top of brainstem
Releasing & inhibiting hormones → controls pituitary
👑
Pituitary
Base of brain, sella turcica
GH, TSH, FSH, LH, ADH, Oxytocin — controls other glands
🦋
Thyroid
Front of neck (butterfly shape)
Thyroxine (T3/T4) — metabolic rate, growth
🔵
Parathyroid
Behind thyroid (4 small glands)
PTH — calcium & phosphate balance
🟠
Adrenal
Top of each kidney
Cortex: cortisol, aldosterone | Medulla: adrenaline
🔶
Pancreas (Islets)
Behind stomach
Insulin (β) → glucose ↓ | Glucagon (α) → glucose ↑
♂
Testes
Scrotum
Testosterone — male characteristics
♀
Ovaries
Pelvic cavity
Oestrogen, Progesterone — female characteristics
🌙
Pineal
Deep in brain (epithalamus)
Melatonin — circadian rhythm (sleep/wake)
Concept Map
Click any branch node to explore its details. Build a mental map of the chapter.
Control & Coordination
🔌 Nervous System
🧪 Endocrine System
🌿 Plant System
Neuron Structure
Reflex Arc
Human Brain
Hormones
Tropic Movements
Nastic Movements
📚
ACADEMIA AETERNUM
तमसो मा ज्योतिर्गमय · Est. 2025
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Control & Coordination Class 10 Notes | Quick Revision
Control & Coordination Class 10 Notes | Quick Revision — Complete Notes & Solutions · academia-aeternum.com
Control and Coordination is a vital life process in living organisms, helping them sense and respond to stimuli, regulate functions, and maintain balance. This chapter explores how humans and plants control their body activities, highlighting systems like the nervous and endocrine systems in animals, and the roles of hormones and growth responses in plants. With real-life examples, labelled diagrams, and concepts like reflex action, plant tropisms, and feedback mechanisms, students learn how…
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