NRVOUS SYSTEM OF PERIPLANETA AMERICANA
Central nervous system ,
Peripheral nervous system and
Autonomous nervous system.
1) CENTRAL NERVOUS SYSTEM:–
The central nervous system of periplanata consists of a nerve ring , and
Double ventral nerve cord.
NERVE RING :-
The nerve ring is present around the oesophagus. It is formed by the brain , sub-oesophageal ganglion and circum-oesophageal connectives.
- Brain :–
- Brain is the spra-oesophageal ganglion. It lies above the oesophagus.
- Brain has three lobes. They are protocerebrum , deutocerebrum and tritocerebrum.
- The protocerebrum receives sensory impulses from the compound eyes throughoptic nerves; Deutocerebrum receives sensory impulses from antennae through antennal nerves; and tritocerebrum receives sensory impulses from the labrum. Hence brain is principally sensory in nature.
- Sub-oesophageal ganglion :-
- Sub-oesophageal ganglion lies below the oesophagus.
- It controls the movement of mouthparts, legs and wings. Hence it is the principal motor center.
- Circum-oesophageal connectives :-
A pair of circum-oesophageal connectives is present around the oesophagus, connecting the tritocerebrum with the sub-oesophageal ganglion.
VENTRAL NERVE CORD :-
- The two ventral nerve cords are solid and ganglionated.
- They arise from the sub-oesophageal ganglion and extend upto the 7th abdominal segment.
- Two nerve cords are connected by a ganglion in each segment .
- In periplaneta total nine ganglion are present on ventral nerve cords. Three are thoracic ganglion and six are abdominal ganglion.
- Three thoracic ganglia are present , one in each thoracic segment.
- The first to the fourth abdominal segments have one abdominal ganglion each.
- The fifth abdominal segment has no ganglion.
- The serially 5th abdominal ganglion is present in the sixth segment and the 6th abdominal ganglion is preent in the seventh segment.
- The last or the sixth abdominal ganglion is the largest of all the abdominal ganglia. It is formed by the fusion of the ganglion of the 7th, 8th , 9th and 10th abdominal segments.
2) PERIPHERAL NERVOUS SYSTEM:-
- The peripheral nervous system consists of nerves that arise or go to different ganglia.
- Brain is the chief sensory organ. It receives a pair of optic nerves, from the compound eyes , a pair of antennal neves fron the antennae and a pair of labral nerves , from the labrum.
- Sub-oesophageal ganglion gives off motor nerves to the mandibles, maxillae, labium, wings and legs. It is the principal motor centre in the body.
- Thoracic ganglia supply nerves to the parts of their respective segments.
- Meta thoracic ganglia send nerves to the first abdominal segment also.
- Nerves from the first four abdominal gangia supply to the organs of the segments 2-6 serially.
- The fifth ganglion present in the 6th abdominal segment innervates the organs of that segments.
- The sixth ganglion present in the 7th abdominal segment innervates the all organs present in 7th – 10th abdominal segments. The organs include the reproductive organs , copulatory appendages besides anal cerci.
3) AUTONOMOUS NERVOUS SYSTEM :-
- This system is also called stomogastric nervous system or visceral nervous system.
- It controls the visceral organs , particularly the muscles of the alimentary canal and the heart.
- The autonomous nervous system includes four ganglia, a frontal ganglion , a hypocerebral ganglion, a visceral ganglion and a proventricular ganglion.
- A frontal ganglion on the dorsal wallof the pharynx, in front of the brain. Hypocerebral ganglion is above the oesophagus behind the brain. A visceral ganglion is on the wall of the crop and a proventricular ganglion is on thegizzard.
- These ganglia contain the somata of the post ganglionic motor neurons. Pregnglionic motor neurons of tritocerebrum go to the frontal ganglion as labor-frontal andfrontal nerve.
- Frontal ganglion is connected to the hypocerebral ganglion by a recurrent nerve.
- Hypocerebral ganglion is connected to the visceral ganglion and in turn the visceral ganglion is connected to the proventricular ganglion.