Control and Coordination — Class 10 Science

"Your body's intelligence: nervous system carries signals; hormones carry instructions; together they keep you alive."

1. About the Chapter

This chapter covers how living things RESPOND to changes:

• Nervous system (fast signals)
• Endocrine system (slow, long-term signals via hormones)
• Brain structure and function
• Reflex action
• Plant responses and hormones

2. Why Control and Coordination?

Stimuli and Responses

• Stimulus: change in environment (light, heat, smell, sound)
• Response: organism's reaction (move, secrete, contract)

Need for Coordination

• Multicellular bodies have many cells
• All cells must work together
• Need signal systems to communicate

3. Human Nervous System

Parts

Central Nervous System (CNS):

• Brain
• Spinal Cord

Peripheral Nervous System (PNS):

• Nerves going to/from CNS

Neurons (Nerve Cells)

Structure:

• Dendrites: receive signals
• Cell body: contains nucleus
• Axon: long fibre that sends signals
• Synapse: gap between two neurons (chemical signals cross)

How a Nerve Signal Travels

1. Stimulus → receptor (e.g., skin cell)
2. Electrical signal travels along dendrites
3. To cell body
4. Down axon (electrical)
5. At synapse, releases CHEMICAL (neurotransmitter)
6. Crosses gap to next neuron's dendrites
7. Continues...

Types of Nerves

• Sensory: bring signals from sense organs TO CNS
• Motor: take signals from CNS TO muscles/glands
• Mixed: both functions

Reflex Action

A FAST, AUTOMATIC response without conscious thought.

Example: Touching a hot pan → hand pulled away IMMEDIATELY

• Signal: hot pan → sensory nerve → spinal cord
• Direct response: spinal cord → motor nerve → muscle
• Hand jerks back BEFORE brain even processes the pain!

Reflex Arc: Receptor → Sensory neuron → Spinal cord (integration) → Motor neuron → Effector (muscle)

This is FASTER than conscious response.

4. Human Brain

Main Parts

1. Cerebrum (front, largest):

• THINKING, MEMORY, INTELLIGENCE
• Voluntary movements
• Sensations
• Language

2. Cerebellum (back, below cerebrum):

• BALANCE, COORDINATION
• Posture

3. Medulla (Brain Stem):

• INVOLUNTARY actions (heartbeat, breathing, blood pressure, digestion)
• Connects to spinal cord

Hindbrain Components

• Medulla: vital functions
• Pons: between medulla and rest of brain
• Cerebellum: balance

Forebrain

• Cerebrum: voluntary actions, thinking
• Hypothalamus: hunger, thirst, body temperature
• Thalamus: relay station

Protection

• SKULL (cranium): hard bone box
• Meninges: 3 layers of protective membranes
• Cerebrospinal fluid (CSF): liquid cushion

5. Endocrine System

What It Is

The system of GLANDS that secrete HORMONES into the bloodstream.

Hormones

Chemical messengers travelling in blood from glands to target organs.

Important Glands and Hormones

Important Diseases

• Diabetes: low insulin → high blood sugar
• Goitre: iodine deficiency → thyroid enlarges
• Hypothyroidism: low thyroxine → tired, gain weight
• Hyperthyroidism: high thyroxine → losing weight, anxiety
• Cretinism: thyroxine deficiency in children → stunted growth

Pituitary — 'Master Gland'

Controls many other glands. Located at base of brain.

6. Plant Hormones

Plants don't have nerves but have hormones called PHYTOHORMONES.

Five Main Plant Hormones

1. Auxins:

• Promote CELL ELONGATION
• Make stems grow toward light (phototropism)
• Discovered by Charles Darwin and son
• Used as weedkillers (in high doses)

2. Gibberellins:

• Promote STEM GROWTH
• Seed germination
• Flowering

3. Cytokinins:

• Promote CELL DIVISION
• Delay leaf ageing
• Found in fruits

4. Abscisic Acid:

• INHIBITS GROWTH
• Promotes leaf wilting
• Closes stomata in drought (water conservation)

5. Ethylene (gas):

• Promotes FRUIT RIPENING
• Causes leaf shedding
• That's why bananas ripen others nearby

7. Tropisms (Plant Movements)

Definition

Plant movements in response to stimuli.

Types

Phototropism: response to LIGHT

• Stems POSITIVE (grow toward light)
• Roots NEGATIVE (grow away from light)

Geotropism (Gravitropism): response to GRAVITY

• Roots POSITIVE (grow downward)
• Stems NEGATIVE (grow upward)

Hydrotropism: response to WATER

• Roots POSITIVE (grow toward water)

Chemotropism: response to CHEMICALS

• Pollen tube grows toward ovule

Thigmotropism: response to TOUCH

• Tendrils coil around supports

8. Worked Examples

Example 1: Reflex Arc

What is a reflex arc?

• Path of nervous signal in a reflex: Receptor → Sensory neuron → Spinal cord → Motor neuron → Effector
• Bypasses brain for FASTER response.

Example 2: Hormone

What does insulin do? Where is it produced?

• INSULIN is produced by PANCREAS.
• Lowers BLOOD GLUCOSE by helping cells absorb glucose.
• Deficiency causes DIABETES.

Example 3: Brain Function

Which part of brain controls breathing?

• MEDULLA (in brain stem).
• Controls INVOLUNTARY actions including breathing, heart rate.

Example 4: Plant Hormone

What does auxin do?

• Causes CELL ELONGATION
• Makes stems grow toward light (phototropism)
• Discovered through experiments with coleoptiles

9. Common Mistakes

1. Cerebrum vs cerebellum

   • CEREBRUM: thinking (largest)
   • CEREBELLUM: balance (smaller, behind)

2. All nervous responses are slow

   • REFLEX is FAST (bypasses brain). Conscious responses slower.

3. Hormones travel via nerves

   • NO. Hormones travel via BLOOD. Nerves carry electrical signals.

4. Plants have nervous system

   • NO. Plants have HORMONES (phytohormones).

5. All glands produce hormones

   • Endocrine glands do. Some glands produce other substances (sweat, milk).

10. Real-World Applications

Medical

• DIABETES treatment: insulin injection
• THYROID disorders: medication
• BRAIN injuries: severe consequences
• Stroke: blood clot in brain

Indian Heroes

• AIIMS hospitals lead in neurology, endocrinology
• Indian doctors do world-class brain surgeries

Agriculture

• Auxins as weed killers
• Ethylene to ripen fruits
• Gibberellins to make plants grow bigger
• Indian agriculture uses plant hormones

Sports

• Adrenaline during competition
• Brain coordination during sports
• Reflex training in athletes

11. Indian Context

Ancient

• Ayurveda discussed nervous and hormonal systems
• Yoga involves brain and body coordination

Modern

• Indian Institute of Science (Bangalore) does neuroscience research
• National Brain Research Centre (NBRC), Manesar
• AIIMS various specialised research

12. Conclusion

Control and Coordination keeps the body WORKING TOGETHER:

• Nervous system = fast electrical signals
• Endocrine system = slow chemical messengers
• Brain = master controller
• Reflexes = automatic protection
• Hormones = body's instructions

In plants:

• Phytohormones coordinate growth
• Tropisms = directional growth responses

Master:

• Neuron and reflex arc
• Brain parts and functions
• Key hormones (insulin, adrenaline, thyroxine)
• Plant hormones and tropisms

Practice 15+ problems. This is HIGH-MARK chapter.

Your body is a symphony — nervous and endocrine systems are the conductors.