It may either increase or decrease the stimulus, but the stimulus is not allowed to continue as it did before the receptor sensed it. Negative Feedback MechanismsĪny homeostatic process that changes the direction of the stimulus is a negative feedback loop. Homeostasis is controlled by the nervous and endocrine system of mammals. Positive feedback loops actually push the organism further out of homeostasis, but may be necessary for life to occur. Homeostatsis is maintained by negative feedback loops. The effector is a muscle (that contracts or relaxes) or a gland that secretes. The receptor senses the change in the environment, then sends a signal to the control center (in most cases, the brain) which in turn generates a response that is signaled to an effector. When a change occurs in an animal’s environment, an adjustment must be made. If the blood’s glucose rises after a meal, adjustments are made to lower the blood glucose level by getting the nutrient into tissues that need it or to store it for later use. For instance, if the body becomes too warm, adjustments are made to cool the animal. A change in the internal or external environment is called a stimulus and is detected by a receptor the response of the system is to adjust the deviation parameter toward the set point. While there are normal fluctuations from the set point, the body’s systems will usually attempt to go back to this point. The goal of homeostasis is the maintenance of equilibrium around a point or value called a set point. Even an animal that is apparently inactive is maintaining this homeostatic equilibrium. It is equilibrium because body functions are kept within specific ranges. It is dynamic because it is constantly adjusting to the changes that the body’s systems encounter. Homeostasis means to maintain dynamic equilibrium in the body. These changes might be in the level of glucose or calcium in blood or in external temperatures.
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