Congestive Heart Failure

CHF is a complex condition with a wide variety of causes and impacts on the body.  The brief paragraph below describes one of the possible harmful reactions that can occur in the body as a result of CHF.

In CHF, the heart fails to efficiently pump blood around the body. The kidneys sense the decreased blood flow. The liver and glands release hormones to try to enhance blood flow by retaining more water in the body. The increased water volume in the blood vessels puts more stress on the heart, which further reduces blood flow to the kidneys and other organs.

The paragraph above describes something called a "feedback loop."  We use the term "feedback loop" because it starts with a deviation (a change) in a bodily condition and then ends with some reactions/responses that impact that same bodily condition.  In other words, the body's reaction "loops" around and provides "feedback" (some sort of alteration) to whatever condition changed in the first place.

Our bodies have a nearly unlimited number of possible feedback loops.  Mostly, but not always, these feedback loops serve to maintain "homeostasis" (keep body conditions stable and within livable ranges).  Feedback loops are also involved in many diseases, like the example above.  We will look at feedback loops throughout Bio 40A, B, and C to study topics as diverse as cancer, muscle growth, metabolic disorders, and sperm and egg creation.

One neat thing about feedback loops is that they help show how diverse organs and cells work together.  In the CHF example above, you see involvement of cells and molecules from the cardiovascular system, urinary system, endocrine system, and more.  This helps to break down the somewhat artificial distinction between "organ systems" and show how all organs and cells are interrelated.

Physiologists use a certain vocabulary for describing feedback loops.  Having this common language allows us to compare different feedback loops, identify the roles of various molecules/cells/organs in feedback loops, and perhaps most importantly, identify therapies or drugs to help patients based on which molecules and cells are contributing to bodily changes.

Watch the video below to gain a brief introduction to feedback loops: