1C - Homeostasis & Feedback Loops

Lesson Overview

  • Title: EXSS 155 Lesson 1C: Homeostasis and Feedback Loops

  • Learning Objectives: By the end of this lesson, students should be able to:

    • Define homeostasis

    • Compare and contrast positive vs. negative feedback

Homeostasis

  • Definition: Maintaining the internal environment within physiological limits.

  • Significance: Major theme throughout physiology.

  • Example: Blood glucose level is maintained within a narrow range of 70-110 mg/dL.

  • Mechanism: Accomplished mostly via feedback loops.

Disruptions to Homeostasis

  • Homeostasis can be continually disrupted by:

    • External stimuli:

      • Intense heat

      • Cold temperatures

      • Lack of oxygen

    • Internal stimuli:

      • Psychological stresses

      • Exercise

  • Impact of Disruptions: Usually mild and temporary.

  • Consequences: If homeostasis is not maintained, it may lead to death.

Feedback Mechanisms

Negative Feedback

  • Definition: A response that reverses the original stimulus.

  • Example: Blood Pressure Control

    • Effector activity leads to a drop in blood pressure, which opposes the initial stimulus of an increase in blood pressure.

Positive Feedback

  • Definition: A response that enhances the original stimulus.

  • Example: Childbirth

    • The positive feedback system reinforces a change in a controlled condition; in childbirth, contractions enhance the progression of labor.