मराठी

Nervous System in Planaria (Flatworm)

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Estimated time: 3 minutes
Maharashtra State Board: Class 12

Key Points: Nervous System in Planaria (Flatworm)

  • Planaria (phylum Platyhelminthes) is the most primitive animal with a Central Nervous System (CNS), located on the ventral side of the body.
  • CNS consists of cephalic ganglion (inverted U-shaped brain-like structure) in the head region with 9 branches on each side, and a pair of Ventral Nerve Cords (VNC).
  • VNC are interconnected by transverse commissures in a ladder-like manner.
  • Peripheral nerve plexus arises laterally from VNC. PNS includes sensory cells arranged in lateral cords and single sensory cells scattered in the body.
  • A pair of photosensory eyes is located on the dorsal side of the brain. Represents evolution from diffused (Hydra) → centralised nervous system (Planaria).
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