Q.Describe nervous system in planaria with well labelled diagram.

Planaria (a flatworm) has a relatively simple but organized nervous system: a bilobed 'brain' (cerebral ganglia) at the anterior end, from which two longitudinal nerve cords run posteriorly along the body, connected a...

Planaria shows a primitive 'ladder-type' nervous system with a bilobed anterior brain and paired longitudinal nerve cords joined by transverse commissures.

Planaria (phylum Platyhelminthes) shows one of the simplest examples of a centralized nervous system in the animal kingdom, often called the 'ladder-type' nervous system. At the anterior end of the body lies a small, bilobed mass of nerve cells called the cerebral ganglia (or 'brain'), formed by concentration of nerve cells, which serves as the main coordinating centre and gives off nerves to the eyespots and other anterior sense organs. From this cerebral ganglion, two main longitudinal nerve cords extend posteriorly along the length of the body, one on either side. These two nerve cords are connected to each other at regular intervals by transverse nerve fibres called commissures, giving the whole system a ladder-like appearance. Fine nerve fibres branch off from the cords and ganglia to supply the body wall, muscles and sensory structures (such as the eyespots for light perception and sensory pits/auricles for chemoreception), allowing coord …