 In this video, we will see how negative feedback system works with other types of control systems to bring about various functions. One such system is positive feedback system. Since it's a feedback system, output is fed back as input into the system just like we saw in negative feedback. The loop of the control system is same as that of negative feedback system except one change here. If there is a disturbance which leads to increase in regulated variable, the system works to further increase the value of the regulated variable. Now this means that positive feedback system will keep on increasing the value of the variable with no end point. This will be hazardous to any system since it can change the variable to non-viable values. Well, to prevent that, physiological systems have made sure that all positive feedback systems work under the ambit of negative feedback system. Thus, when a desired value of variable is reached, the process is stopped. Let us take one example of milk ejection reflex. In milk ejection reflex, the ejection of milk and also the synthesis of milk continues till the baby is suckling. So, the sucking of nipple is sensed and the information is sent to control center leading to increase in the ejection as well as continuous synthesis of milk. Now this feedback loop is kept under check by negative control by hypothalamus. Now as soon as the baby stops sucking the nipple, the information from the sensor stops and also the inhibitory control from hypothalamus takes over to stops this positive feedback loop. So, the thing to remember is that positive feedback systems always work under the loop of negative feedback system otherwise it will be hazardous and it can change the variable to non-viable values. One other system which works together with negative feedback system is feed forward system. These control systems act in anticipatory manner and prevent any change in the regulated variable due to disturbance. You might have noticed that in feedback systems disturbance leads to a change in the regulated variable which is then corrected. So, there is a latent period only after which correction takes place. This is known as lag in the system. Now imagine, could there be a scenario where the internal or external disturbance which can lead to change in the value of the variable is sensed directly and the expected change in the variable is corrected. We will see one example where release of insulin starts after eating food but before entry of glucose in blood vessel. This is the normal negative feedback control system where once food is eaten it is absorbed via gastrointestinal tract and it causes rise in blood glucose concentration which is sensed and the blood glucose concentration is brought back to normal. Now in feed forward control systems the disturbance itself is sensed by control center and the expected change is corrected. So, this loop is the feed forward control. But again you see since it is an anticipated change actual variable values are monitored by negative feedback system. Let us conclude this way. To ensure proper body functions in an effective manner there are multiple control systems but all work under the ambit of negative feedback system.