General Organisation of the Nervous System
Original Editor - Pierre Beunardeau
- 1 Introduction
- 2 Anatomical division
- 3 Functional division
- 4 Cell types of Nervous System
- 5 References
The nervous system commands muscles, controls the functioning of all organs and provides information about the outside world through sensory information. It is the seat of the intellectual faculties.
From an anatomical point of view, we distinguish:
- central nervous system (CNS)
- peripheral nervous system (PNS). 
The nervous system fulfilled three functions:
- Sensitive function: sensory information.
- Effector function: motor / glandular response.
- Sensory-afferent : It receives nerve impulses from sensitive receptors and leads them to the CNS
- Motor-efferent: sensory information : It drives CNS nerve impulses up to the effector organs :
- Somatic : responsible for reflex control and voluntary skeletal muscle.
- Autonomous : innervates involuntary effectors: lise muscle, heart and glands: sympathetic and parasympathetic.
Cell types of Nervous System
Role: Reception or production, conduction and transmission of messages in the form of an electrical signal.
- Cell body or soma
It contains cell bodies, dendrites and axons.
- In the brain it is found in the most superficial regions.
- In the spinal cord, in the anterior and posterior horns
It contains myelinated axons.
In the central nervous system :
- Nuclei: region where bodies neurons come together
- Tracts: package axons that have an origin anda common destination
In the SNC:
- Ganglia: group of neuron cell bodies
- Tracts: Axons that start from a same central origin and which lead throughout the body (cranial or spinal).
2. Glial cells or neuroglia
Closely associated with neurons, more numerous but smaller in size. They are the support of neurons and have other important and unique functions (nutrition, immune ...)
The neuroglia comprises 6 cell types, depending on location, structure and function:
- 4 types in the CNS
- 2 types in the SNP
Peripheral nervous system
Neurolemmocytes or Schwann cells
They are the producers of myelin (substance lipid that forms the myelin sheath + several concentric insulating layers that surround the large axons and facilitate nerve control).
Satellite glial cells
They form a capsule surrounding the cell body of neurons located in the lymph nodes. They provide a large number of support functions.
Central nervous system
They form the myelin sheaths (equivalent to Schwann cells)
Very branched cells, their extensions adhere to neurons and cover the surrounding capillaries and are part of the blood-brain barrier.
Protective role: specialized immune cells. They phagocytose microorganisms,damaged cells and debris from dead neurons.
Epithelial cells that line the cavities central CNS (ventricles with CSF).
They constitute a permeable barrier. It is a source of "stem cells" nerves that can differentiate into neurons or gliocytes.
- Oregon State University. Structure and Function of the Nervous System. Available from :https://open.oregonstate.education/aandp/chapter/12-1-structure-and-function-of-the-nervous-system/
- National Cancer Institute. Organization of the Nervous System. Available from:https://training.seer.cancer.gov/anatomy/nervous/organization/
- Dr Alan Woodruff. The University of Queensland. What is a Neuron ? Available from: https://qbi.uq.edu.au/brain/brain-anatomy/what-neuron
- NCBI. Neuroscience. 2nd Edition. Neuroglial Cells. Available from: https://www.ncbi.nlm.nih.gov/books/NBK10869/ (accessed 2001)