Describe the nervous system of cockroach.

Nervous system in cockroach: 

Nervous system of cockroach is ventral, solid and ganglionated. It consists of central nervous system (CNS), peripheral nervous system (PNS) and autonomous nervous system (ANS). 

Central nervous system (CNS): 

Central nerv ous system consists of nerve ring and ventral nerve cord. 

1. Nerve ring consists of: 

a. a pair of supra-oesophageal ganglia 

b. a pair of circum-oesophageal connectives 

c. a pair of sub-oesophageal ganglia 

(a) Supra-oesophageal ganglia or cerebral ganglia: A pair of supra-oesophageal ganglia is collectively known as the brain. Brain is present in head, above the oesophagus and between antennal bases. Each supraoesophageal ganglion is formed by the fusion of three small ganglia – protocerebram, deutocerebrum and tritocerebrum. 

(b) Circum-oesophageal connectives: Supraoesophageal ganglia are connected to suboesophageal ganglion by a pair of lateral nerves called as circum-oesophageal connectives. Connectives arise from supraoesophagial ganglia. 

(c) Sub-oesophageal ganglia: It is a bilobed and present below the oesophagus, in head. It is also formed by the fusion of three pairs of ganglia.

2. Ventral nerve cord: 

a. It arises from the sub-oesophageal ganglion. It is present along mid-ventral position, in perineural sinus. 

b. It is double ventral nerve cord and consists of nine segmental, paired ganglia. 

c. First three pairs of segmental ganglia are large and known as thoracic ganglia. The other six pairs of segmental ganglia are in abdomen (abdominal ganglia). 

d. 6th abdominal ganglion is the largest and it is present in 7th abdominal segment. 

e. There is no ganglion in 6th segment. 

Peripheral nervous system (PNS):

1. The peripheral nervous system comprises of nerves that arise from various ganglia of CNS 

2. Six pairs of nerves arise from the supraoesophageal ganglia.They supply to the eyes, antenna and labrum. 

3. Nerves arising from the suboesophageal ganglion supply to the mandibles, maxillae and labium. 

4. Nerves arising from the thoracic ganglia supply to the wings, legs and internal thoracic organs. 

5. Nerves from abdominal ganglia go to the abdominal organs of respective abdominal segments. 

6. Autonomic nervous system (ANS): It consists of four ganglia and a retrocerebral complex.

The ganglia are as follows: 

1. Frontal ganglion: It is present above the pharynx and in front of brain. 

2. Hypocerebral ganglion: It is present on the anterior region of oesophagus.

3. Ingluvial ganglion: It is present on crop. It is also called as visceral ganglion. 

4. Ventricular ganglion: It is present on gizzard.