Nervous system Mollusca

simplified diagram of mollusc nervous system

the cephalic molluscs have 2 pairs of main nerve cords organized around number of paired ganglia, visceral cords serving internal organs , pedal ones serving foot. pairs of corresponding ganglia on both sides of body linked commissures (relatively large bundles of nerves). ganglia above gut cerebral, pleural, , visceral, located above esophagus (gullet). pedal ganglia, control foot, below esophagus , commissure , connectives cerebral , pleural ganglia surround esophagus in circumesophageal nerve ring or nerve collar.

the acephalic molluscs (i.e., bivalves) have ring less obvious , less important. bivalves have 3 pairs of ganglia— cerebral, pedal, , visceral— visceral largest , important of 3 functioning principal center of thinking . such scallops have eyes around edges of shells connect pair of looped nerves , provide ability distinguish between light , shadow.