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An antagonist to opioids. It can cause distress and some signs of withdrawal if injected by heroin users, a so-called naloxone challenge.
An opioid (opiate) drug, e.g. morphine or heroin.
Driving force of evolution as described by Darwin. In the competition for resources between individuals in an environment that cannot support all of a population, a natural process of ‘selection’ occurs in which individuals with the most adaptive characteristics are more likely to survive and reproduce.
negative cognitive set
Tendency to construe the world in negative terms; characteristic of a depressed mood.
(in cell metabolism) Also called end-product inhibition. It is the mechanism by which a metabolic pathway is regulated: when the product of the pathway exceeds a critical concentration, it ‘switches off’ an enzyme early in the pathway, thereby preventing further synthesis of the regulatory end-product.
negative feedback system
A system in which a displacement of a variable from a state causes corrective action such as to return the variable to that state.
Another name for a neuron.
The collection of all of the neurons of the body, in brain, spinal cord and periphery.
Dendrites or axons grown from neurons.
A disorder of behaviour or personality brought about by damage to the brain. Sometimes called an organic disorder.
nicotinamide adenine dinucleotide (NAD+)
Hydrogencarrying coenzyme derived from the vitamin niacin.
N-methyl-D-aspartate (NMDA) receptor
One subtype of glutamate receptor, which binds the amino acid glutamate (a major excitatory neurotransmitter) and mediates its effect in neurotransmission. It is named after the dicarboxylic amino acid N-methyl-D-aspartate (NMDA), an agonist of glutamate used extensively to characterise different isoforms of glutamate receptor.
A neuron that is sensitive to tissue damage at its tip. Normally, the first stage in the process of pain.
non-insulin-dependent diabetes mellitus (NIDDM)
The most common form of diabetes mellitus, in which the responsiveness of cells to insulin is diminished. Thus, although insulin may be present at normal (or near-normal) levels, it is not able to effect its normal regulatory role.See also diabetes mellitus (type II).
non-manual social classes
Those who fall into this social class are from professional and managerial occupations; sometimes called white-collar workers.
norm of reaction
The double layer of membranes that surrounds the nucleus.