Explain the concept of homeostatic control by negative feedback with reference to a set point

Homeostatic control through negative feedback is a critical mechanism that helps maintain a stable internal environment in organisms. This process involves several components working together to counteract deviations from a predetermined physiological value known as the set point.

Concept of Set Point

The set point refers to the ideal or target value for a specific physiological variable, such as body temperature, blood pressure, or blood glucose levels. For instance, the set point for normal human body temperature is approximately 37°C (98.6°F). The body continuously monitors these variables and strives to keep them within a normal range around this set point.

Mechanism of Negative Feedback

1. Detection of Deviation: When a physiological variable deviates from its set point—either increasing or decreasing—receptors in the body detect this change. For example, if body temperature rises above the set point, thermoreceptors in the skin and hypothalamus sense this increase.
2. Signal Transmission: The receptors send signals to a control center, typically located in the brain (e.g., the hypothalamus), which processes the information regarding the deviation from the set point .
3. Response Activation: The control center then activates effectors (muscles or glands) to initiate a response aimed at correcting the deviation. Continuing with the temperature example, if the body is too warm, the hypothalamus triggers mechanisms such as sweating and vasodilation (widening of blood vessels) to dissipate heat .
4. Restoration of Homeostasis: As the effectors work to bring the variable back toward its set point, feedback is provided to the control center. Once the desired level is achieved, further activation of effectors is inhibited, effectively stopping the response. This ensures that once homeostasis is restored, the system does not overcorrect .

Example: Blood Glucose Regulation

A classic example of negative feedback is seen in blood glucose regulation. After eating, blood glucose levels rise above the normal range. In response, pancreatic beta cells release insulin, which facilitates glucose uptake by cells and lowers blood sugar levels back toward the set point. Once glucose levels normalize, insulin secretion decreases, preventing hypoglycemia