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Evolution of the nervous system

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Evolution of the nervous system

  1. 1. Nerve Nets – Cnidaria Ex: Hydra- A loosely organized system ofnerves with no central control- Most synapses are electrical- Impulses are bi-directional- Stimulation at any point spreadsto cause movement of entire body
  2. 2. Nerve Cord – Bilateral AnimalsEx: WormsVentral Nerve cords – InvertebrateEx: InsectsDorsal Nerve Cords – ChordatesEx: Fish
  3. 3. First Nervous System Centralization- Cnidaria- Ganglion( ganglia ) -Clusters of nerve cells controlthe ability to perform more complexmotor tasks requiring coordination ex: swimming
  4. 4. Centralization in the Jellyfish– Jellyfishs skirt must open and contract in a coordinated manner for the animal to move through the water.– Nervous system serves as a simple communications network so all parts of the skirt open and then contract at the same time.
  5. 5. Cephalization – concentration of sensory organs & feeding structures at the head or forward-moving portion of an animal• Enlargement of the anterior ganglia that receive this sensory input and control feeding gave rise to the first brains• An anterior brain connected to a nerve cord is the basic design for all organisms with central nervous systems
  6. 6. Ex: earthworms• Dual nerve cord• Two ganglia -
  7. 7. Ex: insects• Parallel nerve cord• Series of ganglia