An instrument for very brief measured exposure of objects to the eye.

Abnormally high heart rate.

A test in which substances are placed on the tongue of a laboratory animal (e.g. a rat) by means of an implanted tube. The reaction of the animal to the substance (e.g. swallowing, mouth wiping) is usually monitored by video.

Tricarboxylic acid cycle (also citric acid cycle or Krebs cycle.) Second of three consecutive metabolic pathways involved in energy production from glucose. Acetyl CoA, formed from pyruvate in the link reaction, is catabolised via a cyclic series of reactions, in which CO₂ and reduced coenzymes are produced. The former is excreted via the lungs and the latter reoxidised via the electron transport chain.

A white blood cell known as a lymphocyte that matures in an organ called the thymus and is responsible for much of the biological response against pathogens.

Guided by a goal or end-point. For example, some have suggested that evolution is guided in this way (though this is not a mainstream view).

An enzyme that replicates telomeres. Telomerase is a specialised reverse transcriptase able to replicate without loss the 5′ end (in a 5′ to 3′ end direction) of each DNA strand in the chromosome.

A term used for the end of the chromosome; simple tandem DNA repeat sequences that make the end of a eukaryotic chromosome.

Adjustment to a different (i.e. higher or lower) environmental temperature. For example, heat acclimatisation involves a more rapid sweating response, an increase in the volume of sweat produced and a reduction in the amount of salt (NaCl) lost via sweating.

The presentation of two stimuli (e.g. a conditional and an unconditional stimulus) at the same time.