Respiratory & Nervous Systems: Cockroach | Additional Study Material for NEET PDF Download

RESPIRATION

(1) Respiratory organ - "respiratory tubules"

(2) Network of respiratory tubules in body.

(3) This network open out side the body by the "spiracles"

(4) 10- pair spiracles

2-pair on thorax

1 pair between prothorax and mesothorax

1 pair between mesothorax and metathorax

8-pair on abdomen on first 8 abdominal segment

All spiracles :- on "Pleurone"

(a) First pair of spiracle of abdomen situated on lateral side of "tergum"

(b) each spiracles :- surrounded by a ring shaped sclerites called

"peritreme". Each spiracle is guarded by a valve and bears cilia  like bristles or filtering the incoming air.

(c) Valve absent in 1-pair spiracles of thorax and abdomen both.

(d) each spiracles open into chamber called "atrium" or tracheal chamber.

(e) The tracheal chambers are connected with several main tracheal trunks which repeatedely branch in to a diffuse network of small trachea.

(f) last branches of trachea called "Tracheal Capillaries" or "tracheoles"

(g) Tracheal capillaries - "Intra - cellular"

(h) Tracheal capillaries closed in a cell called "tracheal end cell."

(i) Long process found in tracheal end cell.

(j) These process deeply merge in tissues of body

(k) Each cell of body is directly in contact with processes, blood does not related with respiration in blood respiratory pigment absent.

(l) During day time - cockroach is less active so osmotic pressure of tissue fluid - low

(m) Tissue fluid rises into tracheoles

(n) exchange of gases during day time by the tissue fluid.

(o) Cockroach is more active in night so O.P. of tissue fluid high so tissue fluid do not enter into tracheoles.

(p) Direct exchange of gases take place

"HISTOLOGY"

Respiratory tubules:-
(A) Spiral rings of chitin occur in the wall of respiratory tubules.they prevent Collapsing.
spiral rings also called "Tenidia".
(B) spiral rings absent in tracheal capillaries.
 

Breathing :-
(a) Several tergosternal muscles extend between the tergites and sternites of all abdominal segments.

(b) When the abdomen expands, atmospheric air gets filled in the tracheal system through spiracles. This is inspiration.

(c) When the abdomen contracts, the air is forced out. This is expiration.

expiration takes place through first pairs of spiracles of thorax and first pairs spiracles of abdomen.

(d) The spiracular valves control and regulate the in and out passages of the air and abdomen.

(e) The cuticle of cockroach is highly permeable to CO₂, but not to O₂

(f) Most of the CO₂ diffuse out from body wall some of CO₂ out through spiracles.

NERVOUS SYSTEM

Three types of nervous system

(1) Central Nervous system:-

(a) Brain ring - It is located in the head around the pharynx, just in front of tentorium.

Its dorsal part is a thick and bilobed supraoesophageal ganglion or "Cerebral ganglion" formed by

fusion of three pairs of cephalic ganglia.

3 pair ganglia
(i) Protocerebrum

(ii) deutocerebrum

(iii) tritocerebrum

Sub-oesophageal ganglion on ventral side of alimentary canal. Sub oesophageal ganglion formed by the fusion
of three pairs of ganglia.

Both ganglia connected to each other by circumoesophageal connective.

(2) Ventral Nerve Cord :- double solid and ladder like.

Nerve cord has nine segmental ganglia. i.e. Three large ganglia in thorax and six in abdomen. Last ganglion is
located in 7^th abdominal segment.

All ganglia formed in embryo stage by the fusion of 2-ganglia. last segmental ganglion formed by fusion of
many ganglia.

"Peripheral Nervous System"

(1) "3-pair of Nerve :- from cerebral ganglion

One pair from protocerebrum - supply-compound eye

One pair deutocerebrum - in antennae

One pair tritocerebrum - in labrum

(2) Three pairs of nerves connect the suboesophageal ganglion with mandibles, maxillae and labium and other
parts of the head and neck.

(3) Six pairs of nerves from prothoracic and five pairs from each of the mesothoracic and metathoracic ganglia innervate different parts of their respective segments.

(4) A single pair of nerves arises from each of the first five abdominal ganglia to innervate muscles, spiracles, heart chambers and other parts in their respective segments.

(5) From the last abdominal ganglion three pairs of nerve arise.

(3) "Autonomous System"

It is divisible into three parts :-

(1) Stomogastric nervous system :- this includes the following five ganglia they all are inter connected with each other by nerves and the nerves arising from these ganglion to innervate the anterior part of gut, as follows this system regulates involuntary activities of foregut.

(a) Frontal ganglion - This is a small median ganglion located dorsally upon the pharynx just in front of brain.

(b) Hypocerebral ganglion - This is also a small median ganglion located dorsally upon oesophagous behind the brain.

It is also connected, by means of two pairs of fine connectives, with two pairs of adjacent endocrine glands.

glands named -

(i) corpora allata

(ii) Corpora cardiac

All three form "retrocerebral complex" (Hypocerebral ganglion + corpora Cardiaca and Corpora allata)

(c) Visceral ganglion:- This is located mid-dorsally upon the crop at about its middle.

(d) Proven tricular ganglia" (last ganglia)

these are two small ganglia, one upon dorsal and the other upon ventral surface of gizzard. Each of these are connected with visceral ganglion by nerve.

These regulate the activity of foregutas"peristalsis"

(2) Spiracular nervous system :-

(a) This controls the activities of spiracles.

(b) A nerve plexus found around the each spiracle. These are connected with segmental ganglia of nerve chord.

(c) These regulate the activity of spiracle.

(3) "Caudal nervous system"

(a) regulates the activity of hindgut, gonads and abdominal appendages

(b) This nervous system formed by the last segmental ganglion of nerve chord.(7th)

(c) This includes certain fine nerves that arise from the last abdominal ganglion and innervate various parts.

Endocrine glands

(I) Inter cerebral endocrine cells - These cells found in cerebral ganglia and secrete to brain hormone.

It regulates the activity of prothorasic gland.

(II) "Corpora cardiaca" It secretes growth hormone in childhood to control the growth of nymph. In adult stage
these gland regulate heart beat.

(III) "Corpora - allata :-

(a) These glands secrete Juvenile hormone - "neotinin" in childhood stage.

(b) Neotinin regulates the growth and differentiation of tissues, preventing ultimately moulting and metamorphosis.

(c) These glands secrete "gonadotropic" hormone in adult stage - It regulate the activity of reproductive
organs.

(IV) Prothorasic gland :-

(a) found only in nymph stage

(b) Secretion of ecdyson hormone in nymph - moulting hormone this hormone induce moulting.

Compound Eyes.

(1) Compound eye made up of 2000 units called spommatidia.

(2) Outer part of ommatidia - hexagonal lens or "corneal lens " which is formed of transparent cuticle.

(3) Just beneath each lens 2 small cells called "corneagen cells"

(4) These secrete lens

(5) At the time of moulting lens also shed from body so cockroach becomes blind for some time

(6) Corneagen cell - secretion of a new lens.

(7) Beneath these cells is a crystalline cone formed by four surrounding conical cells (- vitrellaor conecells)

(8) Crystalline cone - serves as an accessory lens

(9) part of spommatidia up to cone cell known as dioptric part or focusing part.

(10) Beneath the crystalline cone there is a circle of seven cells called "retinular cells"

(11) The inner border of each retinular cell bears microvilli.

(12) The microvilli of the seven rhabdomeres inter digitate to form a long narrow refractile structure called "rhabdome"

(13) Image formed on rhabdome

(14) Region of retinular cells is called receptor region.

(15) A nerve fibres arises from each retinular cell. All nerve fibers of a compound eye together form"optic nerve".

(16) These nerves supply protocerebrum of cerebral ganglion.

(17) Ommatidium surrounded by a "pigmented sheath"

Two Parts

Upper part - irish pigment sheath
Lower Part - retinular pigment sheath

(18) Pigment sheath seperate omatidia from each other

(19) These prevent the light rays entering into one ommatidium from crossing over to the adjacent ommatidia.

Mechanism :- two types of vision
(1) Apposition or mosaic vision :-

(a) Apposition vision form in bright light

(b) Omatidia fully covered by pigmented membrane.
The light rays reflected from an object enter in to a number of ommatidia.

(c) An oblique light ray, that enters into the focussing part of an ommatidium, strikes against its pigment sheath and becomes absorbed

(d) A straight light ray that enters into an ommatidium on the other hand reaches into its receptor region and forms the image of corresponding part of the object.

(e) Thus all the straight light rays entering into an eye from an object form separate images of different parts of the object in the different ommatidia.

(f) The totality of these small image is, however, a compound image of the whole object such an image is called apposition image, It is clear and detailed

(2) "Superposition image" :-

(a) In dim light in nocturnal insects.

(b) In the night, the pigment sheath of ommatidia contracts and shrinks to their bases, hence the light rays can easily cross over from one ommatidium to adjacent ommatidia
(c) complete images are formed in all ommatidia. This results in the formation of blurred superposition of the objects. In cockroach only apposition images are formed (day and night)

No contraction power in pigmented sheath.