Control and Coordination — Class 10 Science

What CBSE examines here (2026-27). This chapter is unchanged by rationalisation — it has always had three in-text question sets (14 questions) and one end-of-chapter Exercise (12 questions). What's changed is how much anatomical detail it actually teaches: the current text never uses the word "cerebrum," and never mentions the pons, thalamus, meninges or cerebrospinal fluid by name — the brain is examined as three regions (fore-brain, mid-brain, hind-brain), described by function. Plant hormones are covered as four, not five — auxin, gibberellins, cytokinins, abscisic acid; ethylene doesn't appear. The endocrine table covers six hormones (growth hormone, thyroxine, insulin, testosterone, oestrogen, adrenaline) — glucagon and progesterone aren't part of it. All of this detail is real biology and correct, but it belongs to a more detailed treatment (Class 11, or NEET prep) than this chapter gives — see the appendix.

"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

The chapter organises the brain into three regions — fore-brain, mid-brain, hind-brain — and describes each by what it does, not by a longer list of named sub-structures.

Fore-brain

The main thinking part of the brain:

• Receives sensory impulses (separate areas for hearing, smell, sight, etc.)
• Association areas interpret this information, combining it with what's already stored in the brain
• Decides on a response and passes it to motor areas, which control voluntary muscles
• A separate area governs the sensation of hunger

Mid-brain and Hind-brain

Together, these control involuntary actions — actions we don't consciously think about.

• Medulla (part of the hind-brain): controls involuntary actions such as blood pressure, salivation and vomiting; connects to the spinal cord
• Cerebellum (part of the hind-brain): responsible for precision of voluntary actions and for maintaining posture and balance — this is what makes walking in a straight line or riding a bicycle possible

Protection

The brain sits inside the skull (a bony box) and is further cushioned by a fluid-filled layer that absorbs shock. The spinal cord is protected by the vertebral column (backbone).

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

This matches the chapter's own Table 6.1 exactly — six hormones, not more:

Glucagon and progesterone are real hormones but aren't part of this chapter's table — don't confuse them with insulin and oestrogen on an exam.

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.

Four Plant Hormones (this chapter's own list)

1. Auxin:

• Synthesised at the shoot tip; promotes CELL ELONGATION
• When light comes from one side, auxin diffuses to the shady side, making those cells grow longer — this is why the shoot bends toward light

2. Gibberellins:

• Like auxins, help in the growth of the stem

3. Cytokinins:

• Promote CELL DIVISION
• Found in greater concentration where cells divide rapidly — fruits and seeds

4. Abscisic Acid:

• INHIBITS growth
• Its effects include wilting of leaves

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 (the chapter names this one explicitly)

Tendrils: growth, not a named tropism in this chapter

Pea plant tendrils coil around a support because the side touching the object grows more slowly than the side away from it. This directional response to touch is commonly called thigmotropism in more detailed treatments, but this chapter describes the mechanism without using that name — don't be thrown if a question describes tendril-coiling without the label.

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?

• Synthesised at the shoot tip; causes CELL ELONGATION
• Diffuses to the shadier side of the shoot, making those cells grow longer — this is why the shoot bends toward light (phototropism)

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.

Appendix — beyond the current chapter

Not required by this chapter's own text, but correct biology used in more detailed treatments (Class 11, NEET prep) and worth knowing.

More detailed brain anatomy

This chapter examines the brain as fore-brain/mid-brain/hind-brain, described functionally. More detailed courses go further:

• Cerebrum: the common name for the bulk of the fore-brain — thinking, memory, voluntary movement
• Pons: a hind-brain structure relaying signals between the medulla and the rest of the brain
• Thalamus: a fore-brain relay station for sensory information
• Meninges: three protective membrane layers around the brain and spinal cord
• Cerebrospinal fluid (CSF): the fluid this chapter simply calls a "fluid-filled balloon," cushioning the brain against shock

A fifth plant hormone

Ethylene, a gas, promotes fruit ripening and is why keeping one ripe fruit near others speeds up their ripening too — not part of this chapter's four hormones (auxin, gibberellins, cytokinins, abscisic acid), but standard in fuller treatments of plant physiology.

Two more hormones sometimes confused with this chapter's table

Glucagon (also from the pancreas) raises blood sugar, opposing insulin. Progesterone (from the ovaries) supports pregnancy. Neither appears in this chapter's own hormone table — don't substitute them for insulin or oestrogen in an answer here.