1-Homeostasis and Feedback Mechanisms

Introduction to Homeostasis

  • Homeostasis: Body's ability to maintain stable internal conditions (equilibrium) despite external changes.

  • Essential for survival; imbalances can lead to disease or death.

  • Example: Blood glucose levels maintained between 70-110 mg/100mL.

Homeostasis Control Systems

  • Nervous System: Uses electrical impulses for rapid, targeted responses.

  • Endocrine System: Uses hormones for slower, widespread, and long-lasting responses.

  • Both systems primarily operate via negative feedback.

Feedback System Components

  1. Controlled Condition: Body parameter to maintain (e.g., temperature, blood glucose).

  2. Stimulus: Change that disrupts the controlled condition.

  3. Receptor: Detects the change; sends information to control centre.

  4. Control Centre: Evaluates change, decides on action; sends commands to effectors.

  5. Effector: Executes the response to restore homeostasis.

  6. Response: Change produced to bring controlled condition back to normal.

Feedback Types

Negative Feedback

  • Opposes the stimulus to restore balance.

  • Commonly used in body systems for conditions needing regular adjustments.

  • Examples: Body temperature, blood glucose, blood pressure, blood pH.

Positive Feedback

  • Enhances the original stimulus, promoting greater changes.

  • Less common, used for rapid, significant changes.

  • Examples: Childbirth, blood clotting.

Examples of Feedback Mechanisms

Negative Feedback Example: Thermoregulation

  • Stimulus: High external temperature.

  • Response: Sweating and blood vessel dilation to cool body.

Positive Feedback Example: Childbirth

  • Stimulus: Baby’s head stretches cervix.

  • Response: Oxytocin release increases uterine contractions until birth occurs.

Summary Points

  • Homeostasis is vital for health; involves continuous monitoring and adjustments.

  • Negative feedback stabilizes conditions; positive feedback amplifies changes for necessary rapid responses.