Nervous system of Cockroach class 11th

When you look at a cockroach you must probably be wondering if they have blood vessels, brains or a nervous system just like humans do. Well, let me first tell you that cockroach do have a nervous system and in this article you will reading about the nervous system of a cockroach. 

Nervous system of cockroach: 

A cockroach is a reflex animal that mean all the responses are in the form of reflex. Cockroach shares the same type of nervous system with an earthworm, but in the case of cockroach it is specialised. The nervous system of a cockroach consist of Central Nervous System (CNS), Peripheral Nervous System (PNS) and Symphathetic Nervous System

The Central Nervous System includes a nerve ring and a nerve cord and the Peripheral Nervous System consist of the nerves that are arising from the Central Nervous System. There is more to this and lets know about this in much more detail. 

Central Nervous System (CNS): 

The Central Nervous System of a cockroach consists of 1. a pair of supra-oesophagael ganglia which is also known as the cerebral ganglia, 2. a pair of sub-oesophageal ganglia, 3. a pair of circum-oesophageal connectives which is also known as commissures and 4. a nerve chord

1. Supra-oesophageal ganglia:

A pair of supra-oesophageal is basically the brain which is located on the dorsal side of anterior part of the oesophagus of the cockroach. The brain is protected by Chitinous Tentorium.  Chitinous Tentorium is where the brain of the cockroach rests. 

Supra-oesophageal ganglia is a bilobed mass which is situated in the head above the oesophagus and in between the bases of the antennae. It is formed by the fusion of three ganglias which are protocerebrum, deutrocerebrum and tritocerebrum. Sensory functions depend on this ganglia. 

2. Sub-oesophageal ganglia:

The sub-oesophageal is also a bilobed mass which is also situated in the head but below the oesophagus. This is also formed by the fusion of three ganglias in the head region. 

The sub-oesophageal ganglion is situated on the ventral side of the oesophagus of the cockroach. It is the motor centre, meaning it controls the movement of muscles, mouth parts, wings and legs of the cockroach. 

3. Circum-oesophageal connectives:

This ganglion arises from the supra-oesophageal. These both are a pair of nerves which are connected to the sub-oesophegeal ganglia that forms a circle around the oesophagus. These are placed on either sides of the oesophagus. 

All the ganglia (the supra-oesophageal, the sub-oesophageal and the circum-oesophageal) forms the nerve ring. 

4. Nerve chord:

Nerve chord is a solid, ganglionated, double ventral cord. It arises from the sub-oesophageal ganglia and it extends throughout the length of the body. It extends along the mid-ventral side. The nerve chord enlarges to form the paired segmental ganglia.

There are two clusters which are closed into a connective tissue sheath. There are also giant nerve chords present in the chord which are long and thick nerve fibres, because of which faster impulses are conducted.

There are three thoracic ganglia and six pairs of abdominal ganglia. The thoracic ganglia is located in the thoracic region. The first thoracic region is called the Prothoracic region, the second one is called the Mesothoracic region and the third one is called the Metathoracic region. These names are given on the basis of their thoracic segments. 

Each of the thoracic segment has a pair of ganglia. First five pairs of the abdominal ganglia are present in the first five abdominal segments but the 6th ganglia is the largest one and goes up to the 7th segment of the abdomen. 

Peripheral nervous system (PNS): 

The Peripheral Nervous System is made up of the nerves that arise from the supra-oesophageal, the sub-oesophageal, the circum-oesophageal and the segmantal ganglia. Basically, PNS is made up of the nerves that arise from the CNS. 

There are three nerves rising from supra-oesophageal which supplies to the eyes, antennae and labrum. There are three nerves rising from sub-oesophageal which supplies to the mouth parts mandibles, maxillae and labium

The thoracic ganglia supplies the nerves to its own segment which are the thoracic muscles, wings, legs and other internal organs which are present in the thorax. The abdominal ganglia supplies the nerves to the abdomen region to control respiration, circulation and the movements of the alimentary canal

Symphathetic nervous system: 

The Symphathetic Nervous System is also known as the Viseral Nervous System or Autonomic Nervous System (ANS) or Stomogastri Nervous System. The Symphathetic Nervous System consists of four ganglions and a reteroerebal complex

Four Ganglions:

The four ganglions are named as Frontal ganglion, Hypocerebral or Occipital ganglion, Ingluvial or Visceral ganglion and Proventricular ganglion

The Frontal ganglion supplies nerves to the Pharynx, Labrum and Clypeus. The Hypocerebral or the Occipital ganglion gives rise to three nerves. From that, two are lateral nerves and one is median nerve. The lateral nerves are connected to Corpora Cardiaca and Corpora Allata (about these we will know in the reteroerebral complex). Both of these are the endocrine glands. The median nerve runs in backwards direction through the oesophagus and joins the Ingluvial or viseral ganglion

The Ingluvial ganglion is present on the crop of the cockroach. The crop is the end of the oesophagus which is used for storing food before the process of digestion takes place. 

The Proventricular ganglion is present on the gizzard of the cockroach. The gizzard is a muscular stomach which contains sharp teeth-like structure which helps in grinding the food to smaller pieces. The gizzard works as teeth for the cockroach. 

Reterocerebral Complex:

There two paired of masses of nervous tissues which are the Corpora Cardiaca and the Corpora Allata. Corpora Cardiaca helps in neurosecretory and regulates the heart beats and peristalic movements whereas, the Corpora Allata secretes hormones which are used in reproduction. 

Inter-cerebral gland cells - The inter-cerebral gland cells releases certain brain hormones which activates the Prothoracic gland. 

Prothoracic glands:

The Prothoracic glands are located in the Prothoracic region which is the first thoracic segment of the cockroach. This gland produces the hormone Ecdysone which required for controlling moulting (Ecdysis) in the nymph stage. 

Moulting is shedding of the skin of the cockroach. The shedding of the skin mostly takes place in the stage where the insect is still immature which is still undergoing metamorphosis (Transformation of an insect from immature to adult stage) and this stage where the skin is shed is called as the nymph stage

The Prothoracic glands starts to fade away once the process of metamorphosis is completed. 

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