Understanding Negative Feedback and Homeostasis

Aug 5, 2024

Free Science Lessons: Negative Feedback

Objectives of the Video

  • Understand negative feedback
  • Describe the components of a negative feedback system
  • Compare negative feedback with positive feedback

Homeostasis

  • Definition: Maintenance of a constant internal environment
  • Examples:
    • Constant blood pH
    • Constant blood glucose concentration
    • Constant core body temperature
  • Concept of dynamic equilibrium:
    • Parameters fluctuate around an optimum level due to small changes in the body.

Negative Feedback Process

  1. Optimum Value: Every parameter has an optimum value.
  2. Stimulus: A change in the parameter from the optimum value is called a stimulus (either increase or decrease).
  3. Receptor: Detects the stimulus and sends signals to the coordinator.
  4. Coordinator:
    • Compares values from various receptors to the optimum.
    • Sends instructions to an effector.
  5. Effector:
    • Often muscles or glands.
    • Carries out a response to restore the parameter back to optimum (e.g., muscle contraction, gland secretion).
  6. Feedback Loop: Changes in the parameter are fed back to the receptor for continuous monitoring.

Mechanisms for High vs. Low Parameters

  • When a parameter is too high, mechanisms are triggered to reduce it (e.g., sweating).
  • When a parameter is too low, different mechanisms are triggered to increase it (e.g., shivering).
  • This separation allows high control over homeostasis.

Homeostatic Systems to Explore

  • Temperature regulation
  • Regulation of blood glucose concentration
  • Regulation of blood water potential

Positive Feedback

  • Definition: A response that increases the change in a parameter.
  • Example: Childbirth
    • Baby's head pushes against the cervix, triggering oxytocin release.
    • Oxytocin causes uterine contractions, increasing pressure on the cervix, leading to more oxytocin release.
    • Positive feedback continues until birth.
  • Characteristics:
    • Clearly defined endpoint.
    • Rarely seen in homeostasis, unlike negative feedback which is continuous and involves numerous examples.