Question

What constitutes a nerve ring in a cockroach?

Answer 1

Hint: Cockroach belongs to phylum- Arthropoda, class- Insecta, subclass- Pterygota, it has jointed appendages, blood containing cavity called haemocoel,it's exoskeleton is made up of chitin,it has two pairs of wings, wings are of dissimilar type. Cockroaches are nocturnal,cursorial ( fast runner and less capacity of flight ). Body is divided into 3 parts: head, thorax and abdomen.

Complete solution:
Body divided into segments called tegmeta, the exoskeleton of chitin plates occurred in each segment. Chitin plate called 'sclerites'. Sclerites are joined to each other by a membrane called 'articular or arthrodial membrane'.
1. Head:
Hypognathus condition: Bent downwards at an angle of 90 degree from the long axis of the body.
2. Nervous system:
Three types of nervous system:
a. Central nervous system
b. Peripheral nervous system
c. Autonomous nervous system.
Central nervous system includes:
Brain ring and central nerve cord.
Brain ring or nerve ring:
It is located in the head around the pharynx.Its dorsal part is a thick and beloved 'supraesophageal ganglion' or 'cerebral ganglion' fusion of three pairs of Cephalon ganglia.
Suboesophageal ganglion on ventral side of alimentary canal.
Both ganglions are connected to each other by circumesophageal connective.

Hence, the supraesophageal ganglion, sub- oesophageal ganglion and circumesophageal connective constitute the nerve ring.

Note:
Cockroaches have 3 types of nervous system- we have discussed above about the central nervous system which has two parts: brain ring and ventral nerve cord. Peripheral nervous system includes all nerves- mixed nerves (motor nerve and sensory nerve) and the Autonomic system is divided into three parts: 1) Stomogastric nervous system 2) Spiricular nervous system 3) Caudal nervous system.