CBSE Class 11 Biology – Neural Control and Coordination | NCERT Study Module & Revision Notes

Course & Examination Details

• Course: CBSE Class 11 Biology
• Prescribed By: Central Board of Secondary Education
• Based On: NCERT
• Unit: Unit V – Human Physiology
• Chapter: Chapter 21 – Neural Control and Coordination
• Chapter Importance: Conceptually important chapter forming the base for coordination, reflexes, behaviour, and nervous regulation in higher classes

Neural Control and Coordination Class 11 Biology – NCERT Study Module & Revision Notes

CBSE Board Examination Relevance

This chapter is frequently assessed through:

• Definitions and distinctions (neuron types, reflex vs voluntary action)
• Structure and functions of brain and neuron
• Pathway of reflex action
• Short notes on nervous system divisions
• MCQs and assertion–reason questions

It also lays the foundation for coordination mechanisms studied further in Class 12 Biology.

Introduction: Neural Control and Coordination

Living organisms respond to changes in their internal and external environment. In humans, coordination is achieved mainly by two systems:

1. Nervous system – fast, short-lived responses
2. Endocrine system – slow, long-lasting responses

This chapter focuses on neural control, explaining how nerve impulses are generated, transmitted, and coordinated to produce appropriate responses.

1. Nervous System

The nervous system controls and coordinates body activities through electrical signals called nerve impulses.

1.1 Functions of Nervous System

• Receives sensory information
• Integrates and interprets signals
• Sends motor commands to effectors
• Maintains coordination and homeostasis
• Enables learning, memory, and behaviour

1.2 Divisions of Nervous System

The human nervous system is divided into:

(A) Central Nervous System (CNS)

• Brain
• Spinal cord

(B) Peripheral Nervous System (PNS)

• Cranial nerves
• Spinal nerves

(C) Autonomic Nervous System (ANS)

• Sympathetic nervous system
• Parasympathetic nervous system

1.3 Central Nervous System

The CNS acts as the control and integration centre.

Brain

• Protected by skull
• Covered by meninges
• Bathed in cerebrospinal fluid

Spinal Cord

• Protected by vertebral column
• Conducts impulses to and from brain
• Controls reflex actions

1.4 Peripheral Nervous System

• Consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves
• Connects CNS with body parts
• Transmits sensory and motor impulses

1.5 Autonomic Nervous System (ANS)

ANS controls involuntary activities such as heartbeat, digestion, and breathing.

Sympathetic Nervous System

• Prepares body for emergencies
• “Fight or flight” response
• Increases heart rate, dilates pupils

Parasympathetic Nervous System

• Conserves energy
• “Rest and digest” response
• Slows heart rate, constricts pupils

2. Neuron

Neuron is the structural and functional unit of the nervous system.

2.1 Structure of Neuron

A typical neuron consists of:

(a) Cell Body (Cyton)

• Contains nucleus and cytoplasm
• Integrates incoming signals

(b) Dendrites

• Short, branched processes
• Receive impulses

(c) Axon

• Long process
• Conducts impulses away from cell body

2.2 Types of Neurons

Based on Function

1. Sensory neurons – carry impulses from receptors to CNS
2. Motor neurons – carry impulses from CNS to effectors
3. Interneurons – connect neurons within CNS

Based on Structure

• Unipolar neurons
• Bipolar neurons
• Multipolar neurons (most common in humans)

2.3 Myelinated and Non-myelinated Fibres

Myelinated Fibres

• Covered with myelin sheath
• Faster conduction
• Found in CNS and PNS

Non-myelinated Fibres

• No myelin sheath
• Slower conduction

Nodes of Ranvier help in saltatory conduction.

3. Nerve Impulse

A nerve impulse is an electrical signal transmitted along the neuron.

3.1 Resting Membrane Potential

• Inside of neuron is negatively charged
• Due to unequal distribution of Na⁺ and K⁺ ions
• Maintained by sodium–potassium pump

3.2 Action Potential

• Stimulus causes depolarization
• Na⁺ channels open → Na⁺ enters
• Inside becomes positively charged

3.3 Repolarization

• K⁺ channels open
• K⁺ moves out
• Resting potential restored

3.4 Transmission of Impulse

Impulse travels along axon and reaches synapse for further transmission.

4. Synapse

Synapse is the junction between two neurons or a neuron and effector.

4.1 Types of Synapse

Electrical Synapse

• Direct ion flow
• Faster transmission

Chemical Synapse

• Uses neurotransmitters
• Unidirectional transmission

4.2 Synaptic Transmission

• Impulse reaches axon terminal
• Neurotransmitter released into synaptic cleft
• Binds to receptors on postsynaptic membrane
• New impulse generated

4.3 Neurotransmitters

Common neurotransmitters include:

• Acetylcholine
• Dopamine
• Serotonin
• Noradrenaline

5. Brain

The brain is the central coordinating organ.

5.1 Major Parts of Brain

The human brain is divided into:

1. Forebrain
2. Midbrain
3. Hindbrain

5.2 Forebrain

Cerebrum

• Largest part
• Controls voluntary actions
• Centre of intelligence, memory, learning

Thalamus

• Relay centre
• Transmits sensory impulses

Hypothalamus

• Controls temperature, hunger, thirst
• Links nervous and endocrine systems

5.3 Midbrain

• Connects forebrain and hindbrain
• Controls visual and auditory reflexes

5.4 Hindbrain

Cerebellum

• Coordinates muscular movements
• Maintains posture and balance

Pons

• Regulates respiration

Medulla Oblongata

• Controls involuntary actions
• Heartbeat, breathing, swallowing

6. Reflex Action

Reflex action is an automatic, quick, involuntary response to a stimulus.

6.1 Characteristics of Reflex Action

• Rapid response
• Involuntary
• Protective in nature
• Controlled mainly by spinal cord

6.2 Reflex Arc

The pathway followed by a reflex action is called reflex arc.

Components of Reflex Arc

1. Receptor
2. Sensory neuron
3. Interneuron
4. Motor neuron
5. Effector

6.3 Examples of Reflex Actions

• Withdrawal of hand from hot object
• Blinking of eyes
• Knee-jerk reflex

6.4 Significance of Reflex Action

• Protects body from injury
• Saves time by bypassing brain
• Maintains posture and balance

7. Coordination Between Nervous System and Effectors

Effector organs include:

• Muscles
• Glands

Motor neurons transmit impulses to effectors, resulting in:

• Muscle contraction
• Gland secretion

8. Disorders of Nervous System

(a) Parkinson’s Disease

• Degeneration of dopamine neurons
• Tremors and rigidity

(b) Epilepsy

• Abnormal electrical activity
• Causes seizures

(c) Alzheimer’s Disease

• Progressive loss of memory
• Degeneration of neurons

Quick Revision Notes (CBSE Exam Focus)

• Nervous system controls rapid responses
• Neuron is structural and functional unit
• Resting potential ≠ action potential
• Synapse ensures unidirectional transmission
• Cerebrum controls intelligence and memory
• Hypothalamus links nervous and endocrine systems
• Reflex action is involuntary and rapid
• Spinal cord controls reflexes

NCERT & CBSE Compliance Confirmation

✔ Strictly based on NCERT Class 11 Biology
✔ Terminology and diagrams as per textbook
✔ No out-of-syllabus content
✔ Ideal for CBSE Class 11 board examinations

Conclusion

The chapter “Neural Control and Coordination” explains how the human nervous system receives, processes, and responds to stimuli. Understanding the structure of neurons, brain regions, synaptic transmission, and reflex actions is essential for mastering Human Physiology and scoring well in CBSE Class 11 Biology examinations.