Physiology Illustration Components of simple feedback loops.
Components of simple feedback loops.
This illustration shows the necessary components of a simple feedback loop. Feedback loops contain a sensor (an organ, a structure, or a group of cells), which senses the amount or concentration of a signal. The signal could be body temperature, plasma osmolality, plasma glucose concentration, the extracellular concentration of an ion, or any other physiological parameter that must be maintained within a narrow limit. The sensor sends information regarding the value of the signal to the controller (integrating center), where the information is compared with an intrinsic value known to the controller. This intrinsic value is referred to as the set point, and is the mean value of the physiological parameter under control. For example, the set point for human body temperature is 37 °C. If the controller detects a difference between the value of the signal it receives from the sensor and the set point, it activates the effector (an organ, a structure, or a group of cells) to perform an appropriate function to bring the value of the signal back close to the set point. If the response mounted by the effector opposes the initial disturbance in the signal, then the feedback loop is referred to as a negative feedback loop. For example, if the body temperature rises significantly above the set point, the effector response is to reduce body temperature to bring it back down close to the set point. If the response mounted by the effector is in the same direction as the initial disturbance in the signal, then the feedback loop is referred to as a positive feedback loop. Negative feedback loops are very common and are responsible for maintaining hemostasis. Most physiological parameters are regulated by negative feedback loops. There are only a few examples of positive feedback loops.
Posted: Sunday, November 1, 2015 Last updated: Sunday, November 1, 2015