| feedback | <physiology> The return of some of the output of a system as input so as to exert some control in the process. (18 Nov 1997) |
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| feedback activation | The activation of an enzyme by an end product of a biochemical pathway in which that enzyme plays a part. For example, the activation of factors VIII and V by thrombin during blood clotting. (05 Mar 2000) |
| feedback control | The regulation of the activity of an enzyme by one of its products. (09 Oct 1997) |
| feedback inhibition | <biochemistry, physiology> The process of the end product of a particular metabolic reaction inhibiting an allosteric enzyme involved in that reaction as the reaction starts again, thus breaking the reaction cycle. (09 Oct 1997) |
| feedback regulation | <physiology> Control mechanism that uses the consequences of a process to regulate the rate at which the process occurs: if, for example: the products of a reaction inhibit the reaction from proceeding (or slow down the rate of the reaction), then there is negative feedback, something that is very common in metabolic pathways. Positive feedback is liable to lead to exponential increase and may be explosively dangerous in some cases. Other examples are the action of voltage dependent sodium channels in generating action potentials and the activation of blood clotting factors V and VIII by thrombin. Without damping, feedback can lead to resonance (hunting) and oscillation in the system. (18 Nov 1997) |
| feedback system | A complex of neuronal circuits whereby a part of the efferent path returns to the input to modulate its activity, thus acting as a governor on the system. See: feedback. (05 Mar 2000) |
| feeder | 1. One who, or that which, gives food or supplies nourishment; steward. "A couple of friends, his chaplain and feeder." (Goldsmith) 2. One who furnishes incentives; an encourager. "The feeder of my riots." 3. One who eats or feeds; specifically, an animal to be fed or fattened. "With eager feeding, food doth choke the feeder." (Shak) 4. One who fattens cattle for slaughter. 5. <physics> A stream that flows into another body of water; a tributary; specifically, a water course which supplies a canal or reservoir by gravitation or natural flow. 6. A branch railroad, stage line, or the like; a side line which increases the business of the main line. 7. <chemical> A small lateral lode falling into the main lode or mineral vein. A strong discharge of gas from a fissure; a blower. 8. <machinery> An auxiliary part of a machine which supplies or leads along the material operated upon. 9. <engineering> A device for supplying steam boilers with water as needed. Source: Websters Dictionary (01 Mar 1998) |
| feeder layer | <cell culture> In order to culture some cells, particularly at low or clonal density, it is necessary to use a layer of less fastidious cells to condition the medium. Often the cells of the feeder layer are irradiated or otherwise treated so that they will not proliferate. In some cases the feeder layer may be producing growth factors or cytokines. (18 Nov 1997) |
| feedforward control | The process in which one of the products of a metabolic pathway induces an enzyme which participates in the metabolic pathway to act. (09 Oct 1997) |
| feeding | Giving food or nourishment. (05 Mar 2000) |
| feeding and eating disorders of childhood | Mental disorders related to feeding and eating that are usually diagnosed in infancy or early childhood. (12 Dec 1998) |
| feeding behaviour | Behavioural responses or sequences associated with eating including modes of feeding, rhythmic patterns of eating, and time intervals. (12 Dec 1998) |
| feeding centre | A region of the lateral zone of the hypothalamus, electrical stimulation of which in the rat elicits uninterrupted eating; destruction of the region causes long-lasting anorexia. (05 Mar 2000) |
| feeding methods | Methods of giving food to humans or animals. (12 Dec 1998) |
| feeding tube | A flexible tube passed through the oral pharynx and into the oesophagus and stomach, through which liquid food is fed. (05 Mar 2000) |