Specialized Cell & External Factors

Of The Nervous System

External Factors That Affect The Nervous System

The nervous system is designed to respond to the environment. It is vulnerable to many of the things found in the environment. Although the amount of damage caused by a dangerous agent depends on the age and genetic substrate of the subject, there is a high chance for selective vulnerability for some areas to specific toxins all levels of the Central Nervous System (CNS). The effects well known environmental toxins such as lead, mercury, etc. and the impact of social damages such as trauma, alcohol, and tobacco on the CNS require close attention. The effect of the hospital and therapeutic environment is now common in view of increased awareness of iatrogenic disorders. Laboratory tests such as examination of CSF and nerve conduction toxicity studies, are also suggested.

Specialized Cells In The Nervous System


  • transmit nerve messages

  • variable in size and shape

  • Three parts

    • Dendrites - receive information from another cell and transmit the message to the cell body.

    • Cell Body - contains the nucleus, mitochondria and other organelles typical of eukaryotic cells.

    • Axon - conducts messages away from the cell body.

  • Three types

    • Sensory neurons - have a long dendrite and short axon, and they carry messages from sensory receptors to the central nervous system.

    • Motor neurons - have a long axon and short dendrites, and transmit messages from the central nervous system to the muscles or to the glands.

    • Interneurons - found only in the central nervous system where they connect neuron to neuron.

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Glial cell (or glia)

  • supportive cell

  • in direct contact with neurons and often surrounds them

  • do not conduct electrical impulses

  • most abundant cell in the central nervous system
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