Control & Coordination Class 10 Notes

Chapter 6 · CBSE Class X

🧠

Control and Coordination

Nervous System Neuron Structure Reflex Action Reflex Arc Human Brain Spinal Cord Endocrine Glands Anomal Hormones Plant Hormones

📖 Introduction

Control and Coordination is a fundamental life process that enables living organisms to detect changes (stimuli) in their internal and external environment and respond appropriately. It involves the integration of different organ systems so that the body functions in a synchronized and efficient manner. This process ensures survival, adaptation, growth, and maintenance of homeostasis (stable internal conditions).

📘 Definition

Control refers to the regulation of various physiological activities in the body, while Coordination refers to the harmonious functioning of different organs and systems in response to stimuli.

In simple terms, it is the mechanism by which organisms receive information, process it, and produce a suitable response.

🏷️ 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)

1

Stimulus is detected by receptors.
2

Information is transmitted to control centres (brain/spinal cord or hormones).
3

Processing and decision-making occurs.
4

Instructions are sent to effectors.
5

Response 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

Example

Daily Life)

Touching a hot object leads to immediate withdrawal of the hand. This is a reflex action controlled by the spinal cord.

Example

Example 2 (Plants)

A plant bends towards light. This is known as phototropism and is controlled by plant hormones.

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

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!"

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.

🧠

ANIMALS – NERVOUS SYSTEM

🧠 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.

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

🧠

Stimulus

📖 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.

basis receptors — Types of receptors detecting stimuli

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

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

🧠

Neurons

📖 Introduction

📘 Definition

🖼️ Figure

Structure of Neuron

(a) Structure of neuron (b) Neuromuscular junction

🗂️ Types / Category

Parts of Neuron

🧠 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.

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.

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.

📌 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

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

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

🧠

Reflex Actions

📖 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

Example

Withdrawal of hand when touching a hot object.

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

🧠

HUMAN BRAIN

📘 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

Example

Solving a mathematical problem involves cerebrum for thinking and reasoning.

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

🧠

COORDINATION IN PLANTS

📘 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.

Gibberellins

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.

Cytokinins

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.

Ethylene

Promotes fruit ripening.
Causes leaf, flower, and fruit fall.
Involved in ageing processes.
Helps in response to mechanical stress and senescence.

✏️ Example

Example

Sunflower turning towards sunlight due to phototropism.

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

🧠

Animal Hormones

📘 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

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

🗂️ 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

Example

After eating food, insulin is released to lower blood glucose levels.

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.

Core Concepts

Formulas & Terms

Practice Questions

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 Impulse

Reflex Arc Direction

Receptor → Sensory Neuron → CNS (Spinal Cord) → Motor Neuron → Effector

Hormone Action Principle

Stimulus → Endocrine Gland → Hormone (via blood) → Target Organ → Response

Phototropism (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.

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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

1

The synaptic cleft is a fluid-filled gap — electricity cannot travel across a fluid medium efficiently.
2

Neurotransmitters allow for signal modulation — the receiving neuron can decide whether to fire based on the combined input from many synapses (summation).
3

This ensures one-directional transmission: neurotransmitters are only stored in the pre-synaptic terminal, preventing backward signals.
4

It 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

1

Correct: Both carry electrical signals; both have a specific direction of current flow; both connect components in the body/circuit.
2

Misleading: Neurons are NOT passive conductors. The signal is an electrochemical impulse (action potential), not a simple electrical current.
3

Misleading: Signal strength does NOT decrease with distance in neurons (unlike wire resistance). The signal is regenerated at each node of Ranvier.
4

Misleading: 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

1

The medulla oblongata controls all vital involuntary functions: cardiac rhythm, respiratory rate, blood pressure, and swallowing.
2

These functions are non-negotiable for survival — stopping them even briefly causes death.
3

The cerebrum controls voluntary actions, thinking, and memory. These can be compensated for partially (unconscious reflex activity continues).
4

Conclusion: 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

1

Hypothesis: Reflex actions are processed in the spinal cord independently of the brain.
2

Procedure: Use an animal model (frog). Destroy the brain (pith the frog) while keeping the spinal cord intact.
3

Observation: When the leg is pinched, the frog still withdraws its leg reflexively.
4

Conclusion: Since the brain is absent yet reflex occurs, the spinal cord alone is sufficient for reflex action.
5

Extension: 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

1

Adrenaline binds to specific receptors on target cells. Different organs have different receptor subtypes (α and β adrenergic receptors).
2

Heart: β1 receptors → increased heart rate and force of contraction.
3

Bronchi: β2 receptors → dilation of airways (more oxygen intake).
4

Digestive system: Mainly α receptors → decreased blood flow, slowed peristalsis.
5

Key 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

1

Endocrine glands lack ducts (tubes). They secrete hormones directly into the surrounding capillaries → bloodstream.
2

Exocrine glands (e.g., sweat, salivary) use ducts to deliver secretions to specific surfaces.
3

Advantage 1: Blood acts as a universal carrier → hormones can reach any organ in the body, not just nearby tissues.
4

Advantage 2: Enables systemic (whole-body) coordination from a single gland.
5

Advantage 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

1

Day 1–2: Light enters from one direction. Auxin (produced at shoot tip) begins migrating to the shaded side.
2

Day 2–3: Shaded side has higher auxin concentration → cells on shaded side elongate faster than illuminated side.
3

Day 4–5: The shoot visibly bends toward the light source (positive phototropism).
4

Mechanism: Differential growth (not turgor change) due to auxin gradient is the cause.
5

If 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

1

Thigmotropism (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.
2

Seismonasty (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.
3

Classification 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

1

Nervous system: Signal travels at up to 100 m/s via electrical impulses. Response in milliseconds.
2

Advantage: Essential when speed is critical. Example: Jerking hand away from fire, blinking when something approaches the eye, catching a falling object.
3

Hormonal system: Hormones travel via blood. Response in seconds to hours.
4

Advantage: For sustained, long-term changes. Example: Puberty changes (months), menstrual cycle regulation (days), growth (years), stress adaptation (hours).
5

Conclusion: 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

1

Argument FOR hypothalamus as master: The hypothalamus controls the pituitary by releasing releasing-hormones and inhibiting-hormones (TRH, GnRH, etc.).
2

Without hypothalamus signals, the pituitary cannot secrete its tropic hormones (TSH, FSH, LH, GH, etc.).
3

The hypothalamus also connects the nervous and endocrine systems — it receives signals from the brain and translates them into hormonal responses.
4

Counter-argument: The pituitary physically governs 7+ endocrine glands simultaneously and is often the point of pathology (e.g., pituitary tumours cause gigantism/Cushing's).
5

Conclusion: 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.)

⛔

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).

⛔

Mistake: Confusing nastic and tropic movements.
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.

⛔

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.

⛔

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.

⛔

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'.

MCQ Quiz

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Question 1 of 15

Match It

Click a term on the left, then its matching description on the right. Match all 8 pairs!

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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

ℹ️

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

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Control & Coordination

🔌 Nervous System

🧪 Endocrine System

🌿 Plant System

Neuron Structure

Reflex Arc

Human Brain

Hormones

Tropic Movements

Nastic Movements

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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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Control and Coordination

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What You Will Learn

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🏆 Exam Strategy & Preparation Tips

Working Mechanism (Stepwise)

Types of Control and Coordination

Concept Flow (Stimulus-Response Pathway)

Main Functions

Working Mechanism

Types of Nervous System

Neuron (Structural and Functional Unit)

Reflex Action and Reflex Arc

Link with Endocrine System

Types of Stimuli

Associated Components

Stimulus–Response Pathway<

Study Roadmap

Structure of Neuron

Types of Neurons

Structure of Motor Neuron

Types of Motor Neurons

Functions of Neurons

Neurogenesis

Synapse

Reflex Arc Pathway

Types of Reflex Actions

Reflex Arc - Animation

Types of Plant Movements

Tropic vs Nastic Movements

Types of Tropic Movements

Plant Hormones (Phytohormones)

Study Roadmap

Types of Animal Hormones

Important Hormones and Functions

Major Endocrine Glands

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Chapter 6 — Control & Coordination

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