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Addiction and neural ageing
Addiction and neural ageing

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Glossary for SD805_2
Browse the glossary using this index

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An enzyme that breaks down lactose.

Garcia effect

A variety of rapid learning which occurs when ingestion of a characteristic food is followed by gastrointestinal upset. The flavour is avoided in the future. The effect is named after its discoverer, John Garcia, and is also termed taste-aversion learning.

gastric inhibitory peptide (GIP)

Hormone released by endocrine cells in the small intestine in response to the presence of fats and glucose. GIP stimulates insulin release.


The unit of genetic information. Most genes code for the production of proteins.

Genetic developments

We must consider mitosis and meiosis when looking at any pphysiological and psychological development. Meiosis is particular responsible for deciding on the birth sex, in that it passes either the XX or the XY gene into the fertilisation process. 


The total genetic material of a cell or organism.


The specific composition of alleles of a single gene, or the entire complement of genes of an organism. The information content that is inherited.

germ cells

The cells in sexually reproducing organisms that give rise to gametes (ova in females and sperm in males). The gametes contain half the number of chromosomes of the somatic cells. When a sperm fuses with an ovum, a zygote is formed which goes on to develop into a new individual.

germ line

The line of cells that give rise to gametes, i.e. synonymous with germ cells. The term expresses the continuity of inheritance via the germ cells as a result of sexual reproduction.


Technical name for the scientific study of the elderly.

Gestalt psychology

A school of psychology which emphasised that our perception of an image is more than the sum of our perception of component features within an image. (‘Gestalt’ is German for ‘pattern or configuration’.) These days, Gestalt is more commonly used to apply to a form of therapy.


Structure from which substances are secreted by the body. Glands can be endorine, secreting hormones into the bloodstrean, or exocrine, secreting (for example) digestive juices into the gut or sweat onto the surface of the skin.

glia (glial cells)

Cells in the nervous system, found in close physical association with neurons. They are not directly involved in transmission of information along neurons, but have a supporting role. Their functions are both metabolic, e.g. regulating the chemical composition of the nervous system, and structural – they are often wrapped tightly around neurons, where their fatty membranes, called myelin, act as electrical insulation.


Hormone produced by alpha cells of the pancreas in response to lowering of blood glucose level. Glucagon stimulates the release of glucose from glycogen and triacylglycerol stores (via glycogenolysis and lipolysis respectively) and also the new synthesis of glucose (gluconeogenesis).


A group of steroid hormones, the most important being cortisol and corticosterone, synthesised by the adrenal gland; they are involved in the regulation of metabolism and resistance to stress conditions.


The new synthesis of glucose from other small molecules (e.g. lactate, pyruvate, glycerol).


A neuron whose activity is particularly sensitive to local glucose level or rate of glucose metabolism.

glucose sparing

Production of ATP by catabolism of fuel molecules other than glucose, e.g. fatty acids.


An amino acid which is not only a constituent of proteins, but also functions as a neurotransmitter; a derivative of glutamine (also an amino acid).

glutathione peroxidase (GPx)

An enzyme that catalyses the oxidation of two molecules of glutathione, a tripeptide made of three amino acids (γ-glutamyl-cysteinyl-glycine) by hydrogen peroxide, to form oxidised glutathione and two molecules of water. This enzyme is very important in protection of haemoglobin from oxidative breakdown.


The polysaccharide storage molecule in humans and other mammals. It is made up of many glucose units joined together. Glycogen is formed predominantly in the liver and in skeletal muscle and is broken down to glucose to provide energy as required.


Breakdown of glycogen to release glucose.


Lipid with covalently attached sugar chains.


First stage in the catabolism of glucose. The end-product of glycolysis is pyruvate.


Protein with covalently attached sugar chains.

Golgi complex

Stack of flattened membranous sacs in which proteins manufactured by the ribosomes are processed and packaged for export out of the cell in secretory vesicles.

grey matter

Part of the brain and spinal cord that is characterised by a relatively greyish appearance. The appearance is due to the high concentration of cell bodies in this region.

See also white matter.

growth hormone

Also called somatotropin. Fundamentally important hormone, which in conjunction with other hormones (insulin, thyroxin, etc.) controls growth, differentiation and the continual renewal of body substances.

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