Control systems are highly important in cellular and whole body levels as they allow regulation of many different organisms. Throughout this essay I will discuss, in detail, three types of control systems; positive feedback, negative feedback and feedforward, and give examples of how each control mechanism is used in different organisms. Positive feedback is a cycle of events that can promote change, whether that is increase or decrease, within the system. Negative feedback is a chain of events that counteract a change that precedes it, in order to stabilise the conditions in a system to a level that promotes optimum physical and chemical conditions. Feedforward is a system that reacts to changes in the external environment, without having been affected by the change in conditions. Feedback is a reactive response, whereas feedforward is pro-active.
Feedforward (open-loop) control is a mechanism used by many organisms to keep their body within an optimal range, which allows for survival.
This works by means of monitoring intracellular and extracellular environment, which allows the system to 'prepare' for differences in the surrounding environment in order to counteract those changes, keeping conditions at an optimum level. Feedforward responds to common differences at a faster rate than uncommon ones. An example I will discuss is an experiment used to determine the use of feedforward sympathetic coronary vasodilation in exercising dogs.
The aim of the experiment was to determine whether or not the activation of coronary smooth muscle ÃÂ²-adrenoceptors resulted in coronary vasodilation in dogs during exercise.
Ten adult male dogs were surgically fitted with polyurethane catheters in the thoracic aorta and coronary sinus, and a flow transducer on the circumflex coronary artery. After a night of fasting, the dogs were put onto treadmills and were given an intravenous mixture of vehicle,