The dorsal side of the body is brown in colour and can be distinguished from the ventral side which is lighter in colour. Peripheral nervous system From the brain 8 to 10 pairs of nerves arises which supply to the prostomium, buccal cavity, and pharynx. The tentacles, parapodia and … Prenatal and postnatal development of the human nervous system. Phylum – Arthropoda 12. NERVOUS SYSTEM: Fig: T.s nerve cord of Pherithima. Systematic Position Phylum: Annelida Class: Oligochaeta Genus: Pheretima Species: posthuma Common Name: Earthworm. 38. Septal nephridia 4. Nervous activities in Earthworm: All earthworm operations are regulated by the nervous system, but not necessarily by the brain. These castings are formed when it goes deep into the hard and closely packed soil. The lateral sides of the pharynx are pushed inside form­ing a narrow horizontal shelf on each side (Fig. Mouth leads into a short, thin walled buccal cavity, which extends to the middle of the third segment and is surrounded by muscle strands. Excretory organs of earthworm are the nephridia. Structure 4. From the pharyn­geal wall running outwardly to the body wall are numerous radial dilatory muscles. The sphincter apertures are situated just dorsal to nerve cord in each septum except the first four segments. 1.98). 1.Central Nervous System: Central nervous system related with cerebral ganglia or brain in the 3 rd segment and ventral nerve cord extending from 5 th segment to 2 nd last. Enteronephric nephridial system of Pheretima is an adaptation for 1. The middle of the seta is swollen and is called the nodulus (Fig. From cerebral ganglia, 8-10 nerves arise and supply to prostomium, buccal chamber, and pharynx. The body wastes of earthworm increases the fertility of the soil. A living earthworm can protrude and retract its buccal chamber, which acts as an. The brown colour is due to the pig­ment porphyrin which is present in the body wall and it protects the body from bright and strong light. From the sub-pharyngeal ganglia, 3 pairs of the nerve arise supply to 2 nd, 3 rd, and 4 th segments. 1.95B). It comprises of a central nervous system, peripheral nerves and receptor organs. 1.96). The internal epithelium is formed of glandular and ciliated cells. The part of the alimentary canal lying between segments 9 to 14 is called stomach. In 1985, the lipid composition of the ventral nerves of earthworm, Lumbricus terrestris of Oligochaeta, was investigated as part of a systematic study of the evolution of the nervous system. It is represented by 13 species in the Indian soil. Integumentary nephridia 39. Gland cells are of two types mucus cells and albumen cells. Habit and habitat •These are nocturnal in habit and live in damp, moist, humus-rich soil of lawns, gardens etc. Stimuli or sensory impulses are conducted to the ventral nerve cord from the receptor through sensory fibers, from where motor impulses are reflected along efferent fibers to contracting muscles. The sensory input and muscular responses are controlled by the ganglia which are arranged segment-wise in the organism. Introduction to Pheretima 2. (a) Central nervous system comprising of a brain or supraoesophageal ganglion, sub-oesophageal ganglion, circumoesophageal connectives and the ventral nerve cord. In normal condition the sphincter muscles remain contracted keeping each coelomic compartment separa­ted from each other. (c) Sympathetic nervous system is formed by a ganglionated sympathetic nerve. Those nerve which arise from different parts of central nervous system are called peripheral nervous system. They have both sensory and motor neurons, like larger animals. Nerve cord arises from the sub-pharyngeal ganglia. The number of setae in each segment varies considerably. Nerve cord is surrounded by epineurium (a common sheath of connective tissue). Typical nephridia 3. Our mission is to provide an online platform to help students to discuss anything and everything about Zoology. This is followed by a much thicker longitudinal muscle layer, running in parallel bundles, separated from one another by connective tissue and strengthened by collagen fibres. The role of the typhlosole is to increase the surface of absorption. The coelomic compartments remain filled with a milky-white coelomic fluid. Nerve ring is an oblique ring around the pharynx in 3. Colloquially, they are also called nerve cells. The outer covering of ventral nerve cord is called peritoneum. The soil upon which it feeds, passes through the body and are deposited as castings. b. The last segment, at its posterior end bears the anus. Peripheral nervous system: It includes nerve fibers or nerve, which arises from central nervous system. Setae are present in all segments except the first, last and the clitellar segments. 3.15.4.1.4.1 Oligochaeta. Oesophagus is a straight, narrow, long and thin-walled tube. Integumentary nephridia 39. When the circular muscle fibres contract, the diameter of the body becomes narrow and the earth­worm elongates. Also known as autonomic nervous system it consists of : Nerve Plexus Spread beneath epidermis and alimentary canal and connected with peripharyngeal connectives. These cells are small and are as numerous as the phagocytes. Being built on a metameric plan, the locomotion of earthworm is the result of co-ordinated movements. Conservation of water 3. 1.Central Nervous System: Central nervous system related with cerebral ganglia or brain in the 3 rd segment and ventral nerve cord extending from 5 th segment to 2 nd last. Habit and habitat •These are nocturnal in habit and live in damp, moist, humus-rich soil of lawns, gardens etc. Elimination of water 4. Nervous System of Pheretima: The nervous system of Pheretima is well developed. It is primarily made of a single type of cell called the neuron. 8 to 10 pairs of nerve arise from brain which communicates or innervate or supply to prostomium, buccal cavity and pharynx. The body is made up of a series of 100-120 similar segments. The leaves or vegetable matters are seized by the pointed end of the mouth, the buccal chamber is everted and the food is drawn in by the suc­tion of the pharynx. The information and the response could be simple, subtle or complex. ; The epidermis of clitellar segments i.e.,14 th, 15 th, and 16 th segments contain 3 kinds of glands, they are unicellular mucous glands that produce mucus for copulation. The stimuli from the skin are transmitted by sensory fibres to the nerve cord and the stimulus is transferred either to an association neuron first, or it may go to the muscles (effectors) which cause them to contract. Content Guidelines 2. Enteronephric nephridial system of Pheretima is an adaptation for 1. Contractions keep blood circulatingin one direction.• Smaller blood vessels supply the gut, nerve cord, and thebody wall. 13. The first body segment is called peristomium (Greek : peri, around; stoma, mouth) which bears the mouth aperture on the ven­tral surface. While burrow­ing, the earthworm makes the soil loose and porous. These are minute openings of the integumentary nephridia that open on the ventral surface of the body. This is caused by contraction of circular muscles and relaxa­tion of longitudinal muscles of that region. Blood glands are present on the 4th, 5th and 6th segments which produce blood cells and haemoglobin. 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