Nervous System- Chapter 6 (Class 7 - Concise Biology Selina) ICSE

 

Nervous System- Chapter 6

(Class 7 - Concise Biology Selina) ICSE

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Keywords:

·  Neurons: Specialized cells that transmit nerve impulses.

·  Brain: The control center of the nervous system, located in the skull.

·  Spinal Cord: A long, thin structure made of nervous tissue, extending from the brain down the back, responsible for transmitting signals between the brain and the rest of the body.

·  Nerves: Bundles of fibers that transmit impulses of sensation to the brain or spinal cord, and from these to the muscles and organs.

·  Central Nervous System (CNS): Comprises the brain and spinal cord.

·  Peripheral Nervous System (PNS): Consists of all the nerves outside the central nervous system.

·  Reflex: An automatic response to a stimulus that is mediated by the nervous system.

·  Synapse: The junction between two nerve cells where impulses pass by diffusion of a neurotransmitter.

·  Sensory Neurons: Neurons that carry signals from the outer parts of your body (periphery) into the central nervous system.

·  Motor Neurons: Neurons that carry signals from the central nervous system to the outer parts (muscles, skin, glands) of your body.

·  Cerebrum: The largest part of the brain, responsible for voluntary activities, intelligence, memory, and emotions.

·  Cerebellum: A part of the brain that coordinates voluntary movements such as posture, balance, coordination, and speech.

·  Medulla Oblongata: The lower half of the brainstem, controlling involuntary functions like breathing, heart rate, and digestion.

·  Autonomic Nervous System (ANS): A part of the peripheral nervous system that controls involuntary body functions, such as heartbeat, blood flow, breathing, and digestion.

·  Reflex Arc: The pathway taken by the nerve impulses during a reflex action.

 

The Nervous System

The nervous system is a complex network of nerves and cells that carry messages to and from the brain and spinal cord to various parts of the body. It is responsible for controlling and coordinating all the activities of the body.

Parts of the Nervous System

1.      Central Nervous System (CNS): This includes the brain and the spinal cord. The brain is the control center of the body, processing information and sending out instructions. The spinal cord acts as a highway, transmitting messages between the brain and the rest of the body.

2.      Peripheral Nervous System (PNS): This consists of all the nerves that branch out from the spinal cord and extend to other parts of the body. It connects the CNS to the limbs and organs.

Functions of the Nervous System

• Sensory Function: The nervous system collects information from the environment through sensory organs (like eyes, ears, and skin) and sends it to the brain.
• Motor Function: After processing the information, the brain sends signals to muscles and glands to respond appropriately (like moving your hand away from something hot).
• Integration: The brain processes and interprets the sensory information to make decisions and coordinate actions.

Types of Nerves

• Sensory Nerves: Carry information from sensory organs to the brain.
• Motor Nerves: Carry instructions from the brain to the muscles.
• Mixed Nerves: Contain both sensory and motor fibers, allowing them to perform both functions.

 Multiple Choice Questions

Question 1

Medulla oblongata controls:

1. Smelling
2. Beating of heart and respiratory movement
3. Intelligence and will power
4. Balancing of the Body

Answer

Beating of heart and respiratory movement

Reason — Involuntary functions of internal organs are controlled by Medulla oblongata.

Question 2

Spinal cord is an extension of:

1. Cerebellum
2. Cerebrum
3. Vertebral column
4. Medulla oblongata

Answer

Medulla oblongata

Reason — Medulla oblongata extends to form spinal cord that runs down to whole length of backbone.

Question 3

Body posture is maintained by:

1. Cerebrum
2. Cerebellum
3. Medulla oblongata
4. Spinal cord

Answer

Cerebellum

Reason — The function of cerebellum includes coordination of muscular activities and balancing of the body.

Short Answer Questions

Question 1

Write one word in the space provided to complete the second pair of the related words pertaining to nervous system:

Memory : cerebrum :               : breathing : ...............

Balance : cerebellum :             : reasoning : ...............

Answer

Memory : cerebrum :               : breathing : medulla oblongata

Balance : cerebellum :             : reasoning : cerebrum

Question 2

(a) Name the two major divisions of the human nervous system.

Answer

The two major divisions of the human nervous system are:

1. The central nervous system
2. The peripheral nervous system

(b) Name the three main parts of the human brain.

Answer

The three main parts of the human brain are:

1. Cerebrum
2. Cerebellum
3. Medulla oblongata

Question 3

Given alongside is the diagram of a neuron. Name the parts numbered 1-5.

Answer

1. Dendrite
2. Nucleus
3. Cyton
4. Axon
5. Terminal Branches

Long Answer Questions

Question 1

With the help of a suitable diagram describe the structure of a neuron.

Answer

A neuron is made up of two main parts —

1. A main cell body called cyton, which gives out a number of fine processes (dendrites)
2. A long process is called the axon.

The cell body contains a nucleus. The dendrites are cytoplasmic extensions of the cell body. They receive messages from the organs and transmit them through the cell body into the axon, which transmits the message. The end of the axon terminates in a number of branches called terminal branches.

The below diagram shows the structure of a neuron:

Question 2

Briefly describe the structure of the cerebrum in the human brain and mention its functions.

Answer

The cerebrum is the largest portion of the brain. It is divided into two halves called the right and left cerebral hemispheres. Each hemisphere is internally hollow. The outer surface of the hemispheres is folded with ridges and grooves which increase the surface of the brain so as to accommodate a large number of neurons.

The cerebrum has the following functions:

1. Intelligence
2. Consciousness
3. Will power
4. Memory

Question 3

Mention the three functions of the spinal cord.

Answer

The three functions of the spinal cord are:

1. To control reflexes below the neck.
2. To conduct messages from the skin and muscles to the brain.
3. To conduct commands from the brain to muscles of the trunk and limbs

Question 4

Describe three kinds of nerves, giving the example of each.

Answer

Three kinds of nerves are:

1. Sensory nerve — It contains only sensory neurons. Example - optic nerve.
2. Motor nerve — It contains only motor neurons. Example - nerves of the muscles of eyeball.
3. Mixed nerve — It is the one that carries both sensory and motor neurons. Example - The nerve that goes to the tongue.

Question 5

What are voluntary and involuntary actions? Which part of the nervous system controls them?

Answer

Voluntary actions — The actions or movements that are under the control of one's own will are called voluntary actions. For example, walking, jumping, lifting books, etc. Voluntary actions are controlled by the Somatic nervous system.

Involuntary actions — The actions or movements that happen without the consciousness or willingness of an individual are called involuntary actions. For example, the beating of the heart, breathing, digestion, etc. Involuntary actions are controlled by the Autonomic nervous system.

Nervous System FAQ:

1. What is the nervous system?

Answer: The nervous system is a complex network of nerves and cells that transmit signals between different parts of the body. It is responsible for coordinating and controlling body activities, including movement, sensation, and thought processes.

2. What are the main components of the nervous system?

Answer: The nervous system is divided into two main parts:

• Central Nervous System (CNS): Consists of the brain and spinal cord.
• Peripheral Nervous System (PNS): Comprises all the nerves that branch out from the CNS and connect it to other parts of the body, including muscles and organs.

3. What is the function of the central nervous system (CNS)?

Answer: The CNS processes information received from the body and coordinates responses. The brain acts as the control center, while the spinal cord serves as a conduit for signals between the brain and the rest of the body.

4. What is the peripheral nervous system (PNS)?

Answer: The PNS connects the CNS to the limbs and organs. It is divided into the somatic nervous system (controls voluntary movements and reflexes) and the autonomic nervous system (regulates involuntary functions like heart rate, digestion, and respiratory rate).

5. What are neurons?

Answer: Neurons are the basic functional units of the nervous system. They are specialized cells that transmit nerve impulses (electrical signals) throughout the body.

6. How do neurons communicate?

Answer: Neurons communicate through synapses, which are small gaps between neurons. When a nerve impulse reaches the end of a neuron, it triggers the release of neurotransmitters, which cross the synapse and bind to receptors on the next neuron, transmitting the signal.

7. What are the main types of neurons?

• Sensory Neurons: Transmit signals from sensory receptors (e.g., skin, eyes) to the CNS.
• Motor Neurons: Send signals from the CNS to muscles and glands, causing action.
• Interneurons: Connect neurons within the CNS and integrate sensory and motor information.

8. What is the autonomic nervous system (ANS)?

Answer: The ANS is a part of the PNS that controls involuntary functions. It has two divisions:

• Sympathetic Nervous System: Prepares the body for "fight or flight" responses.
• Parasympathetic Nervous System: Promotes "rest and digest" functions.

9. What is the role of the brain in the nervous system?

Answer: The brain is the central organ of the CNS, responsible for processing sensory information, regulating bodily functions, and facilitating higher functions like thinking, memory, and emotion.

10. How does the spinal cord function in the nervous system?

Answer: The spinal cord acts as a communication highway between the brain and the body. It also controls quick reflex actions involuntary responses to stimuli.

11. What is a reflex?

Answer: A reflex is an automatic, involuntary response to a specific stimulus. Reflexes are mediated by the spinal cord, allowing for quick reactions without the need for processing by the brain.

12. What are common disorders of the nervous system?

Answer: Multiple Sclerosis (MS): A disease where the immune system attacks the protective covering of nerves.

• Parkinson’s Disease: A disorder affecting movement due to the loss of dopamine-producing brain cells.
• Epilepsy: A neurological disorder characterized by recurrent seizures.
• Alzheimer’s Disease: A progressive neurodegenerative disorder that affects memory and cognitive function.

13. How can I keep my nervous system healthy?

Answer: Maintaining a healthy nervous system involves regular physical activity, a balanced diet rich in vitamins and minerals, adequate sleep, stress management, and avoiding harmful substances like drugs and excessive alcohol.

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