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Tamil Nadu (TNBSE)Class 10 Science★ 4-7 marks in the TN SSLC Class 10 Science public exam through MCQs, diagrams and short/long answers

Nervous System

Samacheer Kalvi (TN State Board) Class 10 Science — Biology Chapter 15, Nervous System. The neuron and nerve impulse, the central and peripheral nervous systems, parts of the brain, reflex action and the reflex arc, and the role of cerebrospinal fluid. Notes with diagrams-in-words, common mistakes, practice and quick revision.

⏱ 20 min readMedium difficulty✓ Free · NCERT-aligned

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By the end of this chapter you'll be able to…

1Describe the structure of a neuron
2Differentiate the central and peripheral nervous systems
3State the functions of cerebrum, cerebellum and medulla
4Explain reflex action and the reflex arc
5State the role of cerebrospinal fluid

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Why this chapter matters

The nervous system explains how we sense and respond to the world. The neuron diagram, reflex arc and brain functions are commonly asked and dependable scoring points in the TN SSLC exam.

Before you start — revise these

A 5-minute refresher here will save you 30 minutes of confusion below.

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Class 9 Science — Control and coordination

Stimulus and response basics.

Nervous System — Class 10 Science (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 10 Science, Biology — Chapter 15. How the body senses, decides and responds.

1. About this chapter

This chapter covers the neuron, the nerve impulse, the central (CNS) and peripheral (PNS) nervous systems, the brain, reflex action, and cerebrospinal fluid.

2. The neuron

The neuron is the structural and functional unit of the nervous system.
Parts: dendrites (receive signals), cell body, and axon (carries the impulse away).
A synapse is the junction between two neurons where impulses pass via chemicals (neurotransmitters).

3. Divisions of the nervous system

Central nervous system (CNS): brain + spinal cord.
Peripheral nervous system (PNS): cranial and spinal nerves; includes the autonomic nervous system (sympathetic and parasympathetic).

4. The brain and CSF

Cerebrum: thinking, memory, voluntary actions.
Cerebellum: balance and coordination of movement.
Medulla oblongata: controls involuntary actions (heartbeat, breathing).
Cerebrospinal fluid (CSF): surrounds and protects the brain and spinal cord and acts as a shock absorber.

5. Reflex action

A reflex action is a quick, automatic response to a stimulus (e.g., withdrawing the hand from a hot object).
The path of a reflex is the reflex arc: receptor → sensory neuron → spinal cord → motor neuron → effector (muscle). It does not wait for the brain, so it is fast.

6. Common mistakes

Mistake: Saying the brain controls reflex actions. Fix: Reflexes are processed by the spinal cord for speed.
Mistake: Confusing cerebrum and cerebellum. Fix: Cerebrum = thinking/memory; cerebellum = balance/coordination.
Mistake: Forgetting the function of CSF. Fix: CSF protects the brain and acts as a shock absorber.

7. Practice (book-back style)

Draw and label a neuron (name three parts).
Differentiate the CNS and PNS.
What is a reflex arc? List its parts in order.
State the functions of the cerebellum and medulla.
What is the role of cerebrospinal fluid?

8. Answer key

Dendrites, cell body, axon (with synapse at the end).
CNS = brain + spinal cord; PNS = nerves connecting the CNS to the body.
Receptor → sensory neuron → spinal cord → motor neuron → effector.
Cerebellum: balance and coordination; medulla: controls heartbeat and breathing.
It surrounds and protects the brain and spinal cord and acts as a shock absorber.

9. Quick revision

Biology Ch 15 · neuron, CNS/PNS, brain, reflex, CSF.
Neuron: dendrites → cell body → axon; synapse between neurons.
CNS = brain + spinal cord; PNS = nerves.
Cerebrum (thinking), cerebellum (balance), medulla (heartbeat/breathing).
Reflex arc (spinal cord) gives fast automatic responses; CSF protects the brain.

Key formulas & results

Everything you need to memorise, in one card. Screenshot this for revision.

Neuron

dendrites → cell body → axon

Unit of the nervous system; synapse between neurons.

Nervous system divisions

CNS (brain + spinal cord) + PNS (nerves)

PNS includes the autonomic system.

Reflex arc

receptor → sensory neuron → spinal cord → motor neuron → effector

Fast, automatic, via the spinal cord.

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Common mistakes & fixes

These are the exact errors that cost students marks in board exams. Read them once, save yourself the trouble.

WATCH OUT

✗ Saying the brain controls reflex actions

✓ Reflexes are processed by the spinal cord for speed.

WATCH OUT

✗ Confusing cerebrum and cerebellum

✓ Cerebrum = thinking/memory; cerebellum = balance/coordination.

WATCH OUT

✗ Forgetting the function of CSF

✓ CSF protects the brain and acts as a shock absorber.

NCERT exercises (with solutions)

Every NCERT exercise from this chapter — what it covers and how many questions to expect.

Multiple choice questions

MCQs on neuron, brain parts and reflex.

Questions

Diagram / short answer

Neuron diagram, reflex arc and brain functions.

Questions

Long answer questions

Nervous system divisions and reflex action.

Questions

Practice problems

Try each one yourself before tapping "Show solution". Active recall > rereading.

Q1EASY· Recall

Name three parts of a neuron.

▶ Show solution

Dendrites, cell body and axon.

Q2MEDIUM· Comparison

Differentiate the CNS and PNS.

▶ Show solution

CNS is the brain and spinal cord; PNS is the network of nerves connecting the CNS to the rest of the body.

Q3MEDIUM· Concept

What is a reflex arc? List its parts in order.

▶ Show solution

The nerve pathway of a reflex: receptor → sensory neuron → spinal cord → motor neuron → effector (muscle).

Q4EASY· Recall

State the functions of the cerebellum and medulla.

▶ Show solution

Cerebellum: balance and coordination; medulla oblongata: controls heartbeat and breathing.

Q5EASY· Concept

What is the role of cerebrospinal fluid?

▶ Show solution

It surrounds and protects the brain and spinal cord and acts as a shock absorber.

Q6MEDIUM· Reasoning

Why is a reflex action faster than a normal response?

▶ Show solution

Because it is processed directly by the spinal cord through the reflex arc, without waiting for the brain to decide.

5-minute revision

The whole chapter, distilled. Read this the night before the exam.

•Biology Chapter 15 of Samacheer Kalvi Class 10 Science.
•Neuron: dendrites → cell body → axon; synapse between neurons.
•CNS = brain + spinal cord; PNS = nerves.
•Cerebrum (thinking), cerebellum (balance), medulla (heartbeat/breathing).
•Reflex arc via spinal cord gives fast automatic responses.
•CSF protects the brain and spinal cord.

Tamil Nadu (TNBSE) marks blueprint

Where the marks come from in this chapter — so you can plan your prep.

Typical chapter weightage: 4-7 marks across MCQ, diagram and short/long answers

Question type	Marks each	Typical count	What it tests
MCQ	1	1-2	Neuron, brain parts, reflex
Short / Diagram	2-3	1-2	Neuron diagram and reflex arc
Long Answer	3-5	0-1	Nervous system divisions

Prep strategy

Draw and label a neuron
Memorise brain part functions
Learn the reflex arc sequence
Note that reflexes use the spinal cord

Where this shows up in the real world

This chapter isn't just an exam topic — it lives in the world around you.

Health and neurology

Understanding the nervous system underlies treating disorders and injuries.

Safety reflexes

Reflexes protect us from harm before conscious thought.

Sports and coordination

The cerebellum's role in balance matters in physical skills.

Exam strategy

Battle-tested tips from teachers and toppers for this chapter.

Label the neuron diagram clearly
Write the reflex arc in correct order
Match each brain part to its function
State CSF's protective role

Going beyond the textbook

For olympiad aspirants and curious learners — topics that build on this chapter.

Compare voluntary and involuntary actions with examples.
Explain how an impulse crosses a synapse.

Where else this chapter is tested

CBSE board isn't the only one — other exams test this chapter too.

TN SSLC Class 10 Public ExamHigh

Foundation / NTSE BiologyMedium

School unit testsHigh

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Questions students ask

The real ones — pulled from the Q&A community and tutor sessions.

The spinal cord triggers a reflex action through the reflex arc almost instantly, while the slower pain sensation reaches the brain a moment later.

The tiny junction between two neurons across which a nerve impulse is passed using chemical neurotransmitters.

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