What are the two missing words? The response made by the body to a change in the external environment helps to keep the internal environment constant. For example, once the level of blood glucose returns to normal the responses the body triggered will be stopped. The process of stopping a response once an effective change has been made is called __________ __________.

Sure, let's break down the question step by step to find the two missing words.

1. Understanding the context: The question is about the body's response to changes in the external environment and how it maintains a constant internal environment. This is a fundamental concept in physiology.

2. Key concept: The process described involves the body stopping its response once the desired effect (e.g., normal blood glucose levels) has been achieved. This is a regulatory mechanism.

3. Identifying the process: The process of stopping a response once an effective change has been made is a type of feedback mechanism. Specifically, it is a negative feedback mechanism, where the response reduces or shuts off the original stimulus.

4. Filling in the blanks: The term that fits this description is "negative feedback."

So, the two missing words are "negative feedback."

The complete sentence is: "The process of stopping a response once an effective change has been made is called negative feedback."