NERVOUS SYSTEM 

Nervous system is the complex network of nerves and nerves cell that conway impulses to and from the brain and spinal cord to varios part of body.

Nervous tissue:- Nervous tissue is the type of tissue which composed by the neurone and neuroglia which mainly act in control and coordination of body by the transmission of impulses. 

Neuron

Neurons have the property of electrical excitability, it has ability to initiate nerves impulses in response to stimuli and transmit the impulses from one part of the body to another part. 

 

Structure of neurons.   

The neurons has three part 

  i) The cell body 

 ii) Dendrites 

 iii) An axon

I) The cell body:- the cell body contains a single nuclear surrounded by the cytoplasm, which included organelles such as mitochondria, golgi bodies, lysosome and neurofibrils.

* Neurofibrils:- A nework of thread called neurofibril. 

* The Dendrites and axon are the nerve fibres in the nerves cell. 

II) Dendrites :- Dendrites are the short and branched extensions of the cell body (like tree) that receive and carry the incoming impulses toward cell bodies. 

III) Axons :- The axon which carry the nerves impulses away from the cell body.

        They are usually longer than dendrites sometimes as long as 100m. 

* Axon terminal :- The axon begins singly but many branches and it has many fone extensions at its end called axon terminals. 

According to structure

Unipolar :-  in this neuron have only one extension from the cell body this single extension divided into two branches a central branches and another peripheral branches. Central branches function as axon and peripheral branches function as dentroides.

Bipolar:- This type of neurone have one dentrites and one axon and they function as recepter cell in special sence organ.

Multipolar:-  Multipolar neurons are the neuron that have several dentrides and one axon. Most neuron in brain and spinal cord are of this type.

According to Function

Afferent:- These nerves transmit the impulses from the peripheral part of body to brain and spinal cord. These nerves are unipolar  in nature. It is also known as Sensory nerves. 

Efferent:- The motor nerves originate in the brain and spinal cord and they transmit the impulses to various part of body. It is also known as motor nerves.

Mixed nerves:- In the spinal cord sensory and motor nerves are arranged in seprate group or track, however outside the spinal cord when the sensory and motor nerves are enclosed within the same sheet of connective tissue is called mixed nerves.

Nervous System