Nervous System
Neurons
The nervous system monitors the body and allows responses to be made. The neuron, or nerve cell, is
the basic unit of communication in vertebrate nervous systems.
Three classes of neurons work together:
- Sensory neurons are receptors for specific sensory stimuli.
- Interneurons in the brain and spinal cord integrate input and output signals.
- Motor neurons send information from integrator to muscle or gland cells (effectors).
Neuroglia cells protect, support, and assist neurons. They make up more than half the volume of the
vertebrate nervous system. A variety of cells metabolically assist, structurally support, and
protect the neurons.
Neuron Structure
The cell body contains the nucleus and metabolic machinery for protein synthesis.
Dendrites are numerous, usually short extensions that
receive stimuli (input zones). An axon is usually a single, rather long extension (conducting zone)
that transmits impulses to other cells at its branched endings (output zones). Signals actually
arise in trigger zones.
This animation (Audio - Important) describes the structure of
a motor neuron.
This animation (Audio - Important) describes
nerve structure.
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