Classification of Nervous System:

1. Central nervous system (CNS)
2. Visceral or sympathetic nervous system
3. Peripheral nervous system

1. Central nervous system (CNS):

a. Brain:

• It is the dorsal ganglionic center of the head supported by the tentorium. It is formed by the union of the ganglia of the first 3 segments of the head. Brain is divided into protocerebrum, deutocerebrum and tritocerebrum.

i. Protocerebrum: Formed by the union of the ganglia of the pre-antennary segment and gives nerve connection to the compound eyes and ocelli.

ii. Deutocerebrum: It is formed from the ganglia of the antennary segment and innervates the antenna.

III. Tritocerebrum: It is formed by the union of ganglia of the third/intercalary segment and is attached anteriorly to the deutocerebrum and posteriorly to the suboesophageal ganglion.

b. Sub-oesophageal ganglion:

• It is the ventral ganglionic center of the head formed by the union of ganglia of the scaphocephalic segments.
• It gives nerves to the mandibular, maxillary, labial segment, labrum, salivary ducts, and part of cervical muscles in the neck region and corpora allata.

c. Ventral nerve cord (VNC):

• Contains a chain of segmented ganglia connected using longitudinal connectives and transverse commissures.
• The thorax has 3 ganglia (Aggregated neurons) and the abdomen has 8 ganglia.
• Thorax Ganglia has nerve connections for the legs, wings, and general muscles.
• Abdominal ganglia gives off nerves to the muscles of its segment.

2. Visceral/sympathetic nervous system

It is divided into three systems:

(i) Oesophageal sympathetic/stomatogastric nervous system: – It is directly connected with the brain which supplies nerves for the anterior part of the alimentary canal (foregut and midgut), heart, and certain other parts. It is dorsal in position.

(ii) Ventral sympathetic nervous system: – Consists of a pair of transverse nerves that are connected with each ganglion of VNC. The transverse nerves pass to the spiracles of that particular segment.

(iii) Caudal sympathetic nervous system: Some additional nerves arise from the posterior compound ganglion of VNC which supplies nerves for the posterior part of the gut and the reproductive system.

3. Peripheral NS:

• It includes all the nerves coming from the ganglia of the CNS and that of the visceral nervous system.