Know about neuroglia cells , their chatacteristics, functions & disorders....

                                       

                                 

NEURONS :

ü  Excitable cells

ü  Generate action potential

ü  Is the basic structural & functional unit of the nervous system

ü  Present in CNS,PNS &ANS. 

GLIAL CELLS :

                                     

ü Non excitable cells

ü Do not generate action potential

ü Supporting connective tissue

ü Present mainly in CNS

GLIOGENESIS

ü In the primitive organisms, neurons used to do glial functions but as their specialization  took place they became perfect elements for signaling & information processing .

ü There housekeeping function went to these glial cells first in “ PLATYHELMINTHES 

CHARACTERISTICS:

• They can replace themselves.

•They can divide throughout life.

•Much smaller than neurons but more numerous.

Make up half the mass of brain.

CLASSIFICATION:

CNS:

ØAstrocytes

ØOligodendrocytes

ØMicroglia

Ependymal

PNS:

ØSchwann cells

ØSatellite cells

        ASTROCYTES

§Forms the blood brain barrier.

§Senses when neuron releases glutamate.

§Forms scar like tissue following a CNS injury.

§Involved  in synapse formation in developing  neural tissue. 

 

                   SATELLITE CELLS

•Surround neuronal cell bodies within ganglia.

•Regulate neural environment.

•Found in PNS.

•Support and protect neurons.

OLIGODENDROCYTES & SCHWANN CELLS:

                                      

•They both provide myelination to axons to insulate them.

•MYELIN = PHOSPHOLIPID  bilayer derived from cell membranes

• Myelin prevents the action potential to escape out from the neuron.

        EPENDYMAL CELLS:

                                                         

•These are simple cuboidal or columnar   epithelium in the ventricles of the brain.

• They secrete CSF via the anterior choroid plexus.

•They bear cilia to circulate cerebro spinal fluid.

 DISORDERS OF NEUROGLIAL CELLS :

• Neuroglia cells are self replicating cells  located in between the neurons.

•They make more than half of the mass of the brain.

•Therefore, uncontrolled growth causes brain tumour.

•In adults over 45 years of age, 90%  of all brain tumors are called as “GLIOMAS”.

•GLIOMAS = A general category of tumors which includes :

•Oligodendrogliomas

                        

•Astrocytomas

                           

•Ependymomas