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

This communication allows for such actions as: muscle contraction, thoughts to proceed, actions to be made, and others.

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.


  • These are the 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:

1.)  Microglia

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

2.)  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

3.)  Ependymal

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

4.)  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

5.)  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

6.)  Satellite

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