Junction between cells in the nervous system, and also between such cells and their target organs, e.g. muscles. A synapse consists of a specialised presynaptic membrane from which molecules of neurotransmitter can be released, a gap across which the neurotransmitter diffuses (synaptic cleft) and a postsynaptic membrane that has receptor molecules on it which are specific for and so bind the neurotransmitter.

Space between two cells at a synapse.

Process of new synapse formation.

Combining of effects. A synergism of cannabis and alcohol would be a combination of effects, each reinforcing the other, e.g. in producing the incapacity to drive a car.

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).