Tuesday, November 11, 2014

Homeostasis Deserves Its Own Chapter

Homeostasis is a major theme of every anatomy and physiology course, so why not explore this important principle in a single, focused chapter?

In a recent post, I explained my rationale for chunking Anatomy & Physiology into smaller chapters than are typical among A&P textbooks.  This provides the opportunity to devote a single, compact chapter to the concept of homeostasis.

Starting in the upcoming 9th edition, the second chapter of Anatomy & Physiology is devoted solely to describing the concept of homeostasis and explaining its central role in maintaining normal function of the human body.  This comes after a brief introductory chapter outlining the nature of the human life sciences and the organization of the body.

This reorganization also provides the opportunity to chunk the sections and provide headings and subheadings that help readers understand how various aspects of homeostasis "hang together."

  • Homeostasis
    • The Internal Environment
    • Relative Stability
    • Set Point
    • Models of Homeostasis
  • Homeostatic Control Mechanisms
    • Feedback Loops
    • Basic Components of Control Systems
      • Sensor
      • Integrator
      • Effector
      • Feedback
    • Negative Feedback in Control Systems
    • Positive Feedback in Control Systems
    • Changing the Set Point
    • Feed-Forward in Control Systems
  • Levels of Homeostatic Control
  • Summary of Homeostasis
  • Cycle of Life: Life Span Considerations
  • The Big Picture: Homeostasis
  • Mechanisms of Disease
    • Basic Mechanisms of Disease
    • Risk Factors
  • Case Study

By focusing on homeostasis and the underlying role it plays in nearly all body functions in this manner, students "get it" in a way that helps them move into the remainder of their A&P course with clearer understanding of the big picture.

A few other improvements to coverage of homeostasis in this newly formed chapter include:


  • A brief discussion of circadian rhythms helps students better understand that set points can change in a daily pattern, thus preparing them for such patterns encountered in later chapters
  • Clarification that feedback loops can be understood as stimulus-response mechanisms, which helps students apply homeostatic principles to nervous system applications

Learning Objects

  • A new table listing homeostatic functions of each major body system helps students better visualize the global aspects of homeostasis
  • New set of graphs showing circadian cycles in various physiological variables helps students visualize an important concept, while also introducing them to interpretation of physiological graphs
  • A new diagram representing disease as a loss of homeostatic balance helps student understand the role of homeostasis in health and disease
  • A new case study helps students practice applying concepts of homeostasis to clinical examples

  • More examples of negative-feedback mechanisms, positive-feedback control, feed-forward regulation help students better understand and apply these concepts
  • The model of a tightrope walker (Wallenda model) was added to illustrate concepts of homeostasis missed by the engineered control system model and the fishbowl model of homeostasis
  • A cross-reference to the new A&P Connect article The Human Microbiome helps students integrate the concept of microbial function with the functions of human organs and systems.
  • New boxed content on negative feedback during exercise helps students apply concepts of homeostatic regulation to real-world situations

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