Dictionary,Defintion,Meaning,What is Nerve Ending, Nictitating Membrane, Nipple, Non-Disjunction, Nitella, Node, Non Polar, Nostril

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Home >>Biology Dictionary >> Nerve Ending - Nictitating Membrane

Your Ad Here	Neritic. Of a region of shallow sea water near the coast. Nerve. Bundle of motor and/or sensory nerve-fibers with accompanying connective tissue and blood vessels, in a common sheath of connective tissue. Each nerve fibre conducts impulses independently. A commonly occurring arrangement of these processes is a single long axon which carries impules away from the cell body to other nerve cells or to effecters; and numerous short dendrites which receive impulses from the axons of other nerve cells. Transfer of impulses from nerve cell to nerve cell takes place at synapses. Central nervous system of all animals contains numerous nerve cells.
Some are entirely confined within it, forming an elaborate interconnecting system. Others only partly within it, their thread-like processes running out of it to all parts of the body, some to effecters (motor nerve fibres), some to receptors (sensory nerve fibres). Other nerve cells are situated mainly or wholly outside the central nervous system, e.g. those in nerve nets or sensory nerve cells. (2) This term is sometimes used synonoymously with cell body. Nerve Cell (Neuron, Neruone). (1) Cell of nervous tissue which conducts the impules by which the nervous system functions. Each has a nucleus surrounded by a mass of cytoplasm, constituting the cell body or perikaryon; and projecting from it, thread-liked processes, very various in length and number, which carry the impules from place to place. Nerve Cord. Solid strand of nervous tissue, forming part of central nervous system of invertebrates. In Annelida and Arthropoda there are two parallel ventral nerve cords, each bearing a row of segmentally arranged ganglia.
Nerve Ending. A structure at the peripheral end of a fibre of the peripheral nervous system, in which impulses start (in a sensory fibre) or finish (in a motor fibre). May be merely the bunch of fine branching twigs by which the fibre itself ends bunch or may be a distinct end-organ. Nerve Fibre. The axon of a nerve cell or the similar process (but carrying impules towards the cell body) of many peripheral sensory nerve cells, together with the various special membranes which may surround it. Neural. Relating to nerves or to the nervous system. Neurohumor. A hormone secrted by a Nerve Ending. Neuropil. The mass of Dendrites and Axons surrounding the cell bodies of the central nervous system. Neuston. Organisms supported on the water surface. Neuter. Sexless. Without active reproductive organs but with other parts more or less normal. Niche. A particular role (or set of relationships) of organisms in an ecosystem, which may be filled by different species in different geographical areas. e.g. grass eaters may be Kangaroos in Australia, cattle in Argentina	Your Ad Here
Nicotine. An alkaloid derived from tobacco Nicotinic Acid. (Niacin, P-P Factor) A vitamin of the B group, lack of which is part of the cause of pellagra in amn. Forms part of a respiratory co-enzyme, widely distributed. Required as a vitamin by those vertebrates and insects tested. Synthesived by many micro-organisms Nictitating Membrane. Transparent fold of skin forming a third eyelid. When open, lies at inner (anterior) corner of eye or below lower eyelid. Occurs in some sharks and amphibia and widespread in reptiles and birds. Well developed in few mammals. Nidation. Implantation
Your Ad Here	Nipple. A conical projection at the centre of a mammary of gland which the milk ducts have outlets. Nit. Egg of human louse, which is cemented on to hair Nitella. A genus of green algae Node. That part of a plant stem where leaves are attached or may develop from buds. Non-Disjunction. Failure of the two homologous chromosomes of a pair to separate to opposite poles at the first meiotic division, so that one daughter-cell has both chromosomes and the other neither. Nucellus. The tissue that makes up the greater part of the ovule of seed plants. It contains the embryo sac and nutritive tissue. It is enclosed by the integuments except for a small gap, the micropyle. In certain flowering plants it may persist after fertilization and provide nutrients for the embryo.

Non polar. Bearing no charge or hydroxyl groups, and thus not combining with water.

Nostril. An external opening of the nose leading into the nasal cavity.

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Biology Dictionary - Part 3 Part 4 Primates - Proembryo Prostaglandins - Proteolytic Enzyme Protostele - Pterodactyla (Pterosauria) Purkinje Cells - Pyrenoid Quadrate - Quantasomes Radula - Receptor (Sense-Organ) Rennin - Respiratory Movement Respiratory Pigment - Rhodophyta

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