The scientific investigation of animals, plants and microbes in relation to their natural surroundings, both animate and inanimate.

System comprising living organisms and the physical and chemical factors that make up their environment.

A neuron that carries information from a structure. Often used with respect to the central nervous system to refer to motor neurons.

A behaviour is described as elastic if its performance changes as a function of effort, e.g. if the demands made to gain access to a drug are increased and consumption falls. It is inelastic if, as the demands increase, consumption remains the same.

Concerned with the electrical properties of the skin. Electrical resistance changes with different emotions.

A technique in which electrodes are attached to the head, thus enabling the activity of populations of the brain’s neurons to be monitored. The record of such activity is called an electroencephalogram (also abbreviated to EEG).

Negatively charged particle present in all atoms. The electrons occur in shells surrounding the nucleus.

Chain of molecules (electron carriers) in the inner mitochondrial membrane which are involved in oxidative phosphorylation. Electrons are transferred from NADH and FADH2 to these molecules, then from molecule to molecule along the chain, and are finally accepted by oxygen. ATP formation is coupled to this electron transfer.

A substance made up of only one type of atom.

Response triggered by a stimulus.