Explain the nervous system of a cockroach.

(N/A) $\rightarrow$ The nervous system of a cockroach consists of a series of fused,segmentally arranged ganglia joined by paired longitudinal connectives on the ventral side. Three ganglia lie in the thorax and six in the abdomen.
$\rightarrow$ The upper part of the oesophagus possesses the brain,also known as the supra-oesophageal ganglion. It is formed by the fusion of three ganglia.
$\rightarrow$ Two perioesophageal connectives arise from the brain. They pass along the lateral sides of the oesophagus and connect to the sub-oesophageal ganglion arranged on the ventral side of the body,forming a nerve ring.
$\rightarrow$ The nervous system is spread throughout the body. The head holds only a small part of the nervous system,while the rest is situated along the ventral part of the body. Therefore,if the head of a cockroach is cut off,it can still live for as long as one week.
$\rightarrow$ In the head region,the supra-oesophageal ganglion supplies nerves to the antennae and compound eyes.
$\rightarrow$ Sensory organs of the cockroach include antennae,eyes,maxillary palps,labial palps,and anal cerci.
$\rightarrow$ The compound eyes are situated on the dorsal surface of the head. Each eye consists of about $2000$ hexagonal ommatidia. With the help of these ommatidia,a cockroach receives several images of an object. This kind of vision is known as mosaic vision,which has more sensitivity but less resolution,and is common during the night (hence called nocturnal vision).