NERVOUS SYSTEM
Generalities
The Nervous system is one of the most important systems of the organism, has multiple functions that base  in receiving and process of information proveniente from the surroundings as of the interior of the body with the end to regulate the operation of the other organs and systems

divide  in:
FROM THE POINT OF VIEW ANATOMICO.
	CENTRAL NERVOUS SYSTEM (SNC)
	NERVOUS SYSTEM PERIFERICO (SNP)
FROM THE FUNCTIONAL POINT OF VIEW.
	NERVOUS SYSTEM SOMATICO(SNS)
	NERVOUS SYSTEM AUTONOMO (SNA)

Sistema Nervous Central (SNC)
The central nervous system is constituted bythe  encephalon and the spinal marrow. It finds  protected by three membranes:
 duramadre (External membrane),
 aracnoides(Intermediate),
 piamadre (Internal membrane), designated genéricamente meninges. Besides, the encephalon and the spinal marrow are protected by osseous wrappings, that are the skull and the vertebral column respectively
Functions of the central nervous system:
	Perceive stimuli of the external world.
	Production of impulses effectors or of answer.
	Transmit the nervous impulses (sensitivos and engines).
	Special functions like the memory, understanding and personality.
Peripheral nervous system
 It is the device of the nervous system formed by nerves and neurons that reside or extend  out of the central nervous system (SNC), to the members and organs.1 The main function of the SNP is to connect the SNC to the members and organs. The difference between east and the SNC is in that the peripheral nervous system is not protected by bones or bythe  barrier hematoencefálica, what allows the exhibition to toxins and mechanical damages. The peripheral nervous system is, like this, the one who coordinates, regulates and integrates our internal organs, by means of the axones


Andl Nervous system Somático (SNS)
It consists of peripheral nervous fibres that send sensory information to the central nervous system, and of nervous fibres motoras that project  to the musculo grooved.
Sistema Nervous Autonomous (SNA) 
It is formed by the autonomous parts of the snc and snp.  subdivide Nice and  parasimpática. It regulates the function of the internal organs. (It controls our involuntary actions)
	Nice system: it commissions  to activate to the organism, by what increases the cost of energy and is used to to work during the day.
	System Parasimpático: it Produces the contrary effects to the nice, that is to say, relaxes the organism, diminishes the consumption of energy and is used to to work at night
Neuron:
They are the functional cells of the nervous fabric. They interconnect  forming networks of communication that transmit signals by clear-cut zones of the nervous system . The complex functions of the nervous system are consequence of the interaction between networks of neurons, and no the result of the specific characteristics of each individual neuron.
The form and structure of each neuron relates  with his specific function, the one who can :
•	Receive signals from sensory receptors
•	Drive these signals like nervous impulses, that consist in changes in the electrical polarity to level of his cellular membrane
•	Transmit the signals to other neurons or to cells efectora
In each neuron exist four different zones
•	The pericarion that is the zone of the cell where situates  the core (Fig 1), and from the which are born two types of prolongations (Fig 2)
 
•	The dendritas that are numerous and increase the area of available cellular surface to receive information from the terminal axónicos of others
 
•	The axón that is born only and drives the nervous impulse of this neuron to other cells (Figs 5 and 6) ramificándose in his terminal portion (telodendrón)
 
•	Skilled cellular unions calls sinapsis, situated in places of vecindad narrow between the terminal buttons of the ramifications of the axón and the surface of other neurons (Fig 4 and 5)


TYPES OF NEURONS

• The UNIPOLAR NEURONS: they are embryonic structures originally bipolar, but that have melted his axón and dendrita in an only fibre that, after separating  of the cellular body, goes back to fork  in two branches
The BIPOLAR NEURONS: only they have an axón and a dendrita.
The NEURONS MULTIPOLARES: they possess an axón and several dendritas.
CELULAS OF SOSTEN: NEUROGLIA (SNC)
In the nervous fabric of the SNC, by each neuron there is between 10 to 50 cells of neuroglia , and that unlike the neurons retain his capacity to proliferate.
They exist 4 classes of cells of neuroglia:
	Astrocytes (astroglia)
	oligodendrocitos (oligodendroglia) 
	Cells ependimarias
	microglia
In the nervous fabric of the SNP, so much the neurons, in the ganglions, like the axones situated in the nervous fibres, are surrounded by of cells of sustain.
They distinguish  two types:
	Cells of Schwann
	Cells satellites or capsulares
-Astrocytes:
Celulas In shape of star with numerous prolongations citoplasmaticas (feet perivasculares and membrane limitante glial), possesses a nucleo  clear and cytoplasm with intermediate filaments of proteina acida fibrilar gial (gfap).
Two Types:
	To. Protoplasmic: they Predominate in the grey substance. They possess abundant short cytoplasmic prolongations and ramificadas.
	To. Fibrous: they Predominate in the white substance. They possess fewer prolongations less ramificadas
-Oligondrocitos:
Cells with cores rounded, small, dark and cytoplasm without filaments neither granulos of glucogeno. It possesses fewer prolongations less ramificadas.
Two Types:
	Or. Satelites: Attached to the body of the nervous cell in the grey substance.
	Or. Interfaciculares: In the white substance  forming rows between the nervous fibres.
Function: they Produce  and they keep the pod of myelin in the (snc).
-Microglicocitos (Microglia):
Small cells with a core reduced and dark and thin prolongations citoplasmaticas with fine spines. It is more numerous in the grey substance. It is of mesodermal origin.
Cells microglia, the first and main line of defence of the central nervous system.
-Celulas ependimarias (Ependimocitos):
They are cells cubicas to cylindrical ciliated that form the revestimiento epitelial of the ventricles of the encephalon and of the pipe of the medula spinal. They possess in his portion subapical links and desmosomas dispersos. They lack lamina basal and suffer some modifications in citios especificos of the system ventricular encefalico to produce the clear cefalorraquideo (plexora coroides).
Central channel of the spinal marrow, observe  cells ependimarias and neuroglial.
Cells of sustain of the SNP

	Celulas of S chwann

Rodean All the axomas perifericos conforming the pod  schwann or neurilema. Andn the axomas perifericos greater develop ademas a rich cover in lipidos called pod of myelin, by what existiran nervous fibres mielinicas and amielinicas. Lto region in where they find  two celulas of schwann contiguous lacks myelin and designates  modulate of ranvier.
The extencion of myelin that exists between two nodulos of ranvier sequential calls  segment intermodal. Several axones can be lodged of this form in the same cell. Between the successive cells of schwann exist zones without myelin called the nodes of ranvier.

	CELULAS SATELITES:
They are celulas cubicas pequenas that surround the neural somas in the nervous ganglions. They contribute to establish and keep a microambiente controlled around the body neural in the ganglion, awarding electrical isolation and a road for the exchange metabolico. It does not produce myelin


Organisation of the SNP
Peripheral nerves: it Is a do of nervous fibres that keep  boards by fabric conjuntivo organised in 3 very clear-cut components:
-Endoneuro: Fabric conjuntivo laxo that surrounds each individual nervous fibre.
-Perineurium: Fabric conjuntivo skilled that surrounds each fascículo of nervous fibres (barrier of difucion).
-Epineuro: Fabric conjuntivo dense no modelling that surrounds all a peripheral and full nerve the spaces between the fascículos nervous.