Introduction
The nervous system in humans is the control and coordination system of the body. It receives information from different body parts and surroundings, processes it, and sends instructions to muscles and glands to produce responses.
Example:
- Touching a hot object → Hand immediately moves away.
- Seeing food → Salivary glands start producing saliva.
The nervous system works together with the endocrine system to maintain body activities.
What is the Nervous System?
Definition:
The nervous system is a network of specialized cells called neurons that carry messages (nerve impulses) between different parts of the body and the brain.
Main Functions
- Detect changes inside and outside the body.
- Process information.
- Coordinate body activities.
- Control voluntary and involuntary actions.
- Maintain body balance and responses.
Structure of Human Nervous System
The nervous system is divided into two major parts:
| Division | Main Components | Function |
|---|---|---|
| Central Nervous System (CNS) | Brain and Spinal Cord | Control center |
| Peripheral Nervous System (PNS) | All nerves | Connects body to CNS |
1. Central Nervous System (CNS)
The CNS acts as the main control centre.
Components:
- Brain
- Spinal Cord
A. Brain
The brain is protected by:
- Skull (cranium)
- Three membranes (meninges)
- Cerebrospinal fluid (CSF)
Major Parts of Brain
| Part | Function |
|---|---|
| Forebrain | Thinking, memory, intelligence |
| Midbrain | Visual and auditory reflexes |
| Hindbrain | Balance and involuntary actions |
Forebrain
Functions:
- Thinking
- Learning
- Memory
- Decision making
- Voluntary movements
Main parts:
- Cerebrum
- Thalamus
- Hypothalamus
Midbrain
Functions:
- Controls visual reflexes
- Controls auditory reflexes
- Coordinates body movement
Hindbrain
Components:
- Cerebellum
- Pons
- Medulla Oblongata
Functions:
- Body balance
- Posture
- Breathing
- Heartbeat
B. Spinal Cord
The spinal cord:
- Starts from the brain stem
- Extends down the backbone
- Carries messages between brain and body
Functions
- Conducts nerve impulses
- Controls reflex actions
2. Peripheral Nervous System (PNS)
Peripheral nervous system connects body organs to CNS.
Components:
- Cranial nerves
- Spinal nerves
Functions:
- Carry information to CNS
- Carry commands from CNS
Functional Division of Nervous System
| Type | Function |
|---|---|
| Somatic Nervous System | Controls voluntary actions |
| Autonomic Nervous System | Controls involuntary actions |
Autonomic Nervous System
Further divided into:
| Division | Function |
|---|---|
| Sympathetic | Prepares body for emergency |
| Parasympathetic | Restores normal body conditions |
Examples:
- Increased heartbeat
- Digestion regulation
- Sweating
Neuron – Structural and Functional Unit
Neuron is the basic unit of nervous system.
Structure of Neuron
Parts:
- Dendrites
- Cell body
- Axon
Functions of Parts
| Part | Function |
|---|---|
| Dendrites | Receive signals |
| Cell Body | Process information |
| Axon | Transmit impulses |
Types of Neurons
- Sensory neuron
- Motor neuron
- Relay neuron
Reflex Action
Definition
A reflex action is a rapid and automatic response to a stimulus without conscious thinking.
Example:
- Removing hand from hot object
Reflex Arc Pathway
Stimulus → Receptor → Sensory Neuron → Spinal Cord → Motor Neuron → Effector
Importance
- Fast protection
- Reduces injury risk
Transmission of Nerve Impulse
Process:
- Stimulus received
- Electrical signal generated
- Signal travels through neuron
- Neurotransmitter released
- Next neuron activated
- Response produced
Importance of Nervous System
- Controls body functions
- Maintains coordination
- Enables thinking and learning
- Produces responses
- Helps survival
Quick Summary Table
| Feature | Nervous System |
|---|---|
| Basic Unit | Neuron |
| Main Function | Control and coordination |
| Control Centre | Brain |
| Reflex Centre | Spinal Cord |
| Signal Type | Nerve impulses |
Practice Questions with Answers
Short Answer Questions
1. What is the nervous system?
Answer: A control and coordination system made of neurons that transmits information throughout the body.
2. What are the two major divisions?
Answer: CNS and PNS.
3. What is the functional unit?
Answer: Neuron.
4. Which organ controls reflex action?
Answer: Spinal cord.
5. Name the parts of neuron.
Answer: Dendrites, cell body and axon.
Fill in the Blanks
- The basic unit of nervous system is ________.
Answer: Neuron - The brain and spinal cord form ________.
Answer: CNS - Reflex action is controlled mainly by ________.
Answer: Spinal cord - ________ carries impulses away from cell body.
Answer: Axon - The forebrain contains ________.
Answer: Cerebrum
10 MCQs with Answers
1. Functional unit of nervous system:
A. Muscle
B. Neuron
C. Bone
D. Blood
Answer: B
2. Brain and spinal cord together form:
A. PNS
B. CNS
C. Neuron
D. Reflex
Answer: B
3. Which controls balance?
A. Cerebellum
B. Cerebrum
C. Axon
D. Dendrite
Answer: A
4. Reflex action mainly occurs through:
A. Heart
B. Liver
C. Spinal Cord
D. Kidney
Answer: C
5. Messages travel through:
A. Blood
B. Neurons
C. Bones
D. Muscles
Answer: B
6. Dendrites perform:
A. Receiving signals
B. Digestion
C. Breathing
D. Pumping
Answer: A
7. Autonomic nervous system controls:
A. Involuntary actions
B. Writing
C. Walking only
D. Speaking only
Answer: A
8. Cerebrum belongs to:
A. Forebrain
B. Hindbrain
C. Midbrain
D. Spinal cord
Answer: A
9. Nerve impulse is:
A. Electrical signal
B. Bone movement
C. Blood flow
D. Air pressure
Answer: A
10. Response to stimulus is called:
A. Coordination
B. Reflex
C. Reaction
D. Respiration
Answer: B
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