Life Sciences Glossary: From Nebula to Northern Blot and Notochord

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Nebula

Celestial object resembling a small luminous cloud at a distance comparable with those of the fixed stars.

Noise Pollution

Level of noise is measured in decibels (dB) which is a logarithmic scale of determining sound levels. Noise in excess of 68 dB is considered harmful to human health and in excess of 110 db. Impairs hearing after a prolonged exposure.

Nova

A star whose brightness suddenly increases because of the ejection of a portion of its material. There luminosity of their star may increase up to 10,000 times when there is an explosion of a star. It then becomes a supernova.

Narcotic

A substance that produces insensibility derived from opium.

Natality

The number of individuals entering the population by reproduction per thousand individuals in the population.

Natural Selection

Differential survival and reproduction in nature that favours individuals that are better adapted to their environment.

Nausea

A sensation often leading to the urge to vomit.

Necrosis

Localized tissues death that occurs in groups of cells in response to disease or injury.

Negative Feedback Control

A kind of control mechanisms in which the product of one activity inhibits an earlier step in the chain of events.

Neonatal

The period of time covering the first 28 days after birth.

Neoplasm

Any abnormal growth of new tissue, benign or malignant.

Nephrectomy

The surgical removal of a kidney.

Nephritis

Inflammation and abnormal function of the kidney.

Nephron

A structural and functional unit of kidney consisting of a Bowmanีšs capsule, glomerulus and tubule.

Nerve

One or more bundles of impulse- carrying Fibres (axons or dendrites) that connect the brain and the spinal cord with other parts of the body.

Neuroglia

The supporting or connective tissue cells of central nervous system.

Neuron

A nerve cell.

Neurotoxin

A poison that acts directly on the tissue of the central nervous system such as venom of some snakes.

Neurotransmitter

Any one of the chemicals that modify or result in the transmission of nerve impulses between synapses, e. g. , acetylcholine chloride, gamma- amino butyric acid and norepinephrine.

Neutrophil

A polymorph nuclear granular leucocyte essential for phagocytosis and proteolysis.

Niche

The specific physical space occupied by an organism, the functional role of an organism in ecosystem.

Nicotine

Rapidly acting toxic substance in tobacco.

Nictitating Membrane

A third eyelid found in most reptiles and birds.

Nipple

A small cylindered, pigmented structure that projects just below the center of each breast.

Nisil Body

After Franz Nisil, a structure characteristic of neuron, present in neoplasm rich in RNA and concerned with protein synthesis, trigged granule.

Nocturnal

A life โ€“ style characterized by activity during the night rather than at day.

Nomenclature

A consistent, systematic method of naming used in a scientific discipline to denote classifications, e. g. binomial nomenclature and chemical nomenclature.

Nondisjunction

The failure of homologous chromosomes to separate at anaphase-l of meiosis.

Nonsense Mutation

A mutation that changes a codon specifying an amino acid to a termination codon.

Norepinephrine

An adrenergic hormone that acts to increase blood pressure by vasoconstriction but does not affect cardiac output.

Northern Blot

The transfer of RNA molecules from an electrophoretic gel to a cellulose or nylon membrane by capillary action.

Notochord

An elongated cellular skeletal axis founds in chordate embryo or adult, midventral to nerve cords.

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