11. Study of Animal Type - Cockroach - part 06 - Nervous system

 


11. Study of Animal Type - Cockroach - part 06 - Nervous system


Nervous system :

  • The nervous system of cockroach consists of -
  1. Central Nervous System (CNS)
  2. Peripheral Nervous System (PNS) and
  3. Autonomus Nervous System (ANS). 
  • Nervous system of cockroach is ventral, solid and ganglionated.

A. Central Nervous System (CNS):


  • CNS consists of -
  1. nerve ring and 
  2. ventral nerve cord. 
Nerve ring :
  • Nerve ring  is made up of-  
  1. supraoesophageal ganglia
  2. circum-oesophageal connective and 
  3. sub-oesophageal ganglion.
  • A pair of supra-oesophageal / cerebral ganglia is collectively known as brain. 
  • Brain is present in head, above the oesophagus and between antennal bases. 
  • Each cerebral ganglion is formed by fusion of three small ganglia-
  1.  protocerebrum
  2. deutocerebrum and 
  3. tritocerebrum.


  • Sub-oesophageal ganglion is bilobed; present below the oesophagus in head. 
  • It is also formed by fusion of 3 pairs of ganglia.
  • Cerebral ganglia are connected to suboesophageal ganglion by a pair of lateral nerves called as circum-oesophageal connectives.
  • Connectives arise from cerebral ganglia.

Ventral nerve cord (VNC) : 

  • It arises from sub-oesophageal ganglion. 
  • It is present along mid-ventral position, in perineural sinus.
  • It is double nerve cord and consists of nine segmental, paired ganglia. 
  • First three pairs of segmental ganglia are large and known as thoracic ganglia. 
  • Six pairs of segmental ganglia are in abdomen. 
  • Sixth abdominal ganglion is largest and it is present in 7th abdominal segment. 
  • There is no ganglion in 6th segment.

B. Peripheral Nervous System (PNS):

  • Peripheral nervous system consists of nerves arising from various ganglia of CNS.
  • Six pairs of nerves arise from cerebral ganglia.
  • They go to eyes, antennae and labrum. 
  • Nerves arising from sub-oesophageal ganglion go to mandibles, maxillae and labium. 
  • Nerves arising from thoracic ganglia go to the wings, legs and internal thoracic organs. 
  • Nerves from abdominal ganglia go to the abdominal organs of respective abdominal segments.

C. Autonomous Nervous System (ANS):

  • It consists of four ganglia and a retrocerebral complex. 
  • These 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.

Knowledge Enhancer : 

  • Compound eyes are present in the cockroach, situated on the dorsal surface of the head. 
  • Each eye consists of about 2000 hexagonal ommatidia (singular : Ommatidium). 
  • Each ommatidium is like a simple eye, forming image independently, hence with the help of several ommatidia, a cockroach receives several images of an object.
  • Compound eye gives mosaic or hazy vision, but the animal is able to detect even a slightest movement of the object. 
  • This kind of vision is with more sensitivity but less resolution.

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