Nerve Cell


 
 
Concept Explanation
 

Nerve Cell

Control and coordination in animals depend on two things for information transmission -  chemical signals of hormones and nerve impulses (electrical impulses). If they depended only on electrical impulses through nerve cells, a limited range of tissues would be stimulated. Since they get chemical signals in addition to the nerve impulses, a large range of tissues are stimulated. As a result, animals can show wide-ranging changes in response to stimuli.

Impulse: It is an electrical disturbance received by the dendrite and passed through the cyton to the axon. Messages are transmitted in the form of electrical impulses along the fibres of the neurons.It flows only unidirectionally.

Neurons:  A neuron is the functional and structural unit of kidney.It consists of following parts:

Dendrites or dendrons: These are hairlike processes connected to the cyton. They receive stimulus, which may be physical, chemical, mechanical or electrical, and pass it on to the cyton.

Cyton or Cell body : It's shape may vary from round to stellate . It has large central nucleus surrounded by neuroplasm. Beside other cell organelles cyton contains Nissl's granules.

Axon:  From one side of the cyton arises a cylindrical process filled with cytoplasm. This process is called axon. It is the longest part of the neuron. It transmits impulse away from the cyton. Its tip has a swelling called axon bulb. Generally, a neuron has one axon .Axon is covered with a sheath,made up of schwann cells,called neurilemma. In addition a neuron may be covered with myelinated sheath , such fibres are known as  myelinted sheath fibres  and those without this sheath are termed as  non-myelinated sheath fibres. The ending of an axon may be branched. These endings are called synaptic terminals.

The gap between a synaptic terminal and the dendrite of another neuron or an effector cell is called a synapse. The neurons are not connected. There is minute gap called Synaptic cleft. With in axon there are synaptic vesicles filled with chemicals called neurotansmitters. The impulse that reaches the ends of the axon fibres causes the synaptic vesicles to release neurotransmitters into the synaptic cleft. The neurotransmitter reaches the dendrites of the other neuron. This, sets up a new impulse which is transmitted to the axon. The speed of transmission is 120 m/s.

                                 

Myelinated nerve fibres conduct impulses more efficiently than non-myelinated nerve fibres. The myelinated nerve fibres possess unmyelinated areas at intervals called nodes of Ranvier.

Table : Differences between Dendrites and Axons

S. No Dendrites Axons
1. These are short and tapering processess These are long, uniform and cylindrical processess
2. A number of dendrites arise from the cyton Only single axon arises per cyton
3. They have tapering  ends Terminal branches of the axon enlarge to form a knob
4. They contain NissI's granules and neurofibrils They do no contain NissI's granules but contain neurofibrils
5. They receive sensation and send it to the cyton They carry impulses away from the cyton

A number of nerve fibres are wrapped together to form nerves. The nerves lie end to end in a chain so that the dendrites receive impulse, from an axon or receptor, passes it to the next neuron in the chain via its cyton and axon. The junction between the axon and dendron of the next neuron is called Synapse. It is the point of contact between the terminal branches of the axon of a neuron with dendrites of another neuron. The neurons are not connected. There is a minute gap called Synaptic cleft. Within the axons are synaptic vesicles filled with chemicals called neurotransmitters. Transmission of nerve impulse is a chemical process. The impulse that reaches the ends of the axon fibres causes the synaptic vesicles to release the neurotransmitters (acetylcholine) into the synaptic cleft. The neurotransmitters reach the dendrites of the next neuron. This sets up a new impulse which is transmitted to the axon. The speed of transmission is about 120 m/s. The chemical is soon broken down by an enzyme to make the synapse ready for the next transmission.

Sample Questions
(More Questions for each concept available in Login)
Question : 1

Short and branched outgrowths from the cell body of a neuron are known as _______________

Right Option : B
View Explanation
Explanation
Question : 2

In comparison with other cells, nerve cells show a higher degree of _______________

Right Option : D
View Explanation
Explanation
Question : 3

Junction of two neurons is called _______________

Right Option : D
View Explanation
Explanation
 
Video Link - Have a look !!!
 
Language - Hindi/English
 
Chapters
Simple Harmonic Motion
Cytology
Classifucation Of Plants
Structural Composition Of Plants
Nutrition In Plants, Harmones And Plant Disease
Ecosystem
Classification In Animals
Nutrition In Animals
Human Digestive System
Human Respiratory System
Human Skeleton System
Human Excretory System
Human Nervous System
Human Circulatory System
Human Endocrine System
Human Reproductive System
Genetics
Human Diseases
States Of Matter
Metals And Non Metals
Acid Bases And Salts
Periodic Classification
Fuel, Combustion And Flame
Environmental Chemistry
Rest And Motion
Work Power And Energy
Gravitation
Pressure And Its Effects
Sound and Waves
Heat And Temperature
Light - Reflection
Electricity And Magnetism
Modern Physics
Force And The Laws Of Motion
Light - Refraction
Dispersion And Human Eye
Magnetic Effect Of Electric Current
Atom And Molecule
Pre-Historic Period
Indus Valley Civilization
Vedic Civilization
Religious Reform Movement
The Early Kingdoms
The Mauryan Empire
Post Mauryan Period
The Age Of The Guptas
Post Gupta Era
Age of Rajput
Khilji Dynasty
Slave Dynasty
Tughlaq and Sayyid Dynasty
Vijaynagar Empire And Bahamani Kingdom
Mughal Empire And Beyond
Lodhi Dynasty
Cholas, Chalukyas and Pallavas
Arab Invasions
Bhakti and Sufi Movement
Rise of Sikhs, Jats and Marathas
Administrative Structure of Delhi Sultanate
Architecture During Medivial India
Advent Of The Europeans
Post Mughal Period
Rise of New States in 18th Century
Growth of British Paramountacy
Socio Religious Reforms
Constitutional Development of India
Indian Struggle Against British Rule
The Revolt Of 1857
Education Under British Rule
Role of Press in Freedom Struggle
First Phase of National Movement
Second Phase of National Movement
Third Phase of National Movement
Constitutional Development in India
Constituent Assembly
Union And Its Territory
Structure of Indian Constitution
Fundamental Rights and Duties
The Union Executive
The Union Legislature
Constitutional Amendments and Provisions
Judiciary In India
Emergency Provisions
Center - State Relations
The State Executive
The State Legislature
Election Commission Of India
Constitutional Organisation
Non-Constitutional Organisation
Local Self Goverment
India - Size And Location
Geological History Of India
The Physical Features Of India
Climate Of India
Soils In India
Natural Vegetation
Windlife Conservation In India
Drainage System of India
Irrigation System Of India
Agriculture In India
Livestock And Fisheries In India
Minerals And Energy Resources In India
Means Of Transport In India
Major Industries In India
Tribes of India
Census of India 2011
Music
Dance
Theatre
Pantings
Art, Architecture & Culture of India
Bio-Diversity
Earth And Its Structure
Land Rock And Soil
Atmosphere, Climate And Weather
Oceanography
Human And Regional Geography
Economic Growth And Development
Sectors Of Indian Economy
Economic Planning Of India
Fiscal And Monetary Policy In India
Infrastructure In India
Effects Of British Rule On Indian Economy
National Income
Banking System In India
Poverty And Unemployment
Inflation And Trade Cycles
Major Institutions
Environmental Studies
Chemistry In Everyday Life
Units And Dimensions
Tissues In Organism
Content / Category
Class / Course
 
 
 
Related Videos
Language - Hindi/English
Language - Hindi/English
Language - Hindi/English

Language - Hindi/English
Language - Hindi/English


Students / Parents Reviews [20]