It is a complicated system that is the primary form of communication between cells and organs throughout the body.

The communication allows for muscle contraction, thoughts to procede, actions to be
made, and other reactions.

The nervous system is divided into 2 categories:

1.) Peripheral Nervous System.
2.) Central Nervous System.

Peripheral nervous system (PNS)

The PNS is located distinctly outside the Central nervous system.

The Central nervous system consists of the brain and spinal cords.

The function of the PNS is to allow the central nervous system to connect with the limbs and organs.

 
Central Nervous System

The CNS is found within the meninges of the brain.

The main function of the CNS is the reception of information, the processing of that
information, and often the decision or reaction made to the information.

The CNS is quite complex and the location is extensive

Spinal Cord

The spinal cord is protected by bone of the vertebral column.

The function of spinal cord is the conduction of impulses from the brain to the peripheral nervous system to extremities and back again.

There are 31 segments of the spinal cord.

The complexity of the nervous system is often regulated by
signals and neurotransmitters that transmit from one neuron to another
Neurons are a main component of the nervous system.

 
Neurons

Are cells that react and act in the process of receiving and transmitting information by signaling.
They are an important function of the nervous system.

Neurons themselves can differ greatly – some allow for touch, visual, light, smell, sound
and many others.

Neurons in limbs receive stimuli and transfer or send the signal to the spinal cord and to the brain.

Within the nervous system are several cells with complex responsibilities:

Microglia
   -   Are specialized cells of the Nervous system
   -   Act as macrophages
   -   Can protect neurons
   -   Found in brain and spinal cord
   -   Are mobile

Astrocytes
   -   Are apart of the CNS system
   -   Are shaped in a pattern of a star
   -   Helps maintain the cells of the blood-brain barrier
   -   Helps remedy any injury to the brain
   -   Has a role in scar formation

Ependymal
   -   Are apart of the CNS system
   -   Cells that line the brain and spinal cords
   -   Helps produce cerebrospinal fluid (CSF)

Oligodendroglia
   -   Are an aspect of the CNS system
   -   Similar to Schwann cells of the PNS
   -   Wraps around the axon
   -   Forms the myelin sheath
   -   Can wrap around 40-50 axons

Schwann
   -   Are apart of the PNS
   -   Similar to Oligodendroglia of the CNS
   -   Wraps around the axon
   -   Forms the myelin sheath
   -   Can wrap around only 1 axon
   -   Permits Nodes of Ranvier

Satellite
   -   Are apart of the PNS
   -   Are linear schwann cells
   -   Believed to be similar to Astrocytes in CNS
   -   Supply nutrients to cells