Homeostasis and Feedback Mechanisms

Introduction to Homeostasis

• Definition: The body's ability to maintain a stable internal environment despite external or internal changes.
• Example: Maintaining an internal temperature of 37°C in hot weather (e.g., 40°C in Queensland summer).

Components of Homeostasis

1. Stimulus

   • Definition: Any change in the environment.
   • Example: Increase in temperature when stepping into the heat.

2. Receptors

   • Function: Detect environmental stimuli.
   • Example: Thermoreceptors detect changes in temperature.

3. Afferent Signal

   • Definition: Electrical signal sent towards the control center.

4. Control Center

   • Typically the brain.
   • Function: Evaluates information from receptors and makes decisions.

5. Efferent Signal

   • Definition: Signal sent away from the control center.

6. Effector

   • Function: Creates a change in response to the efferent signal.
   • Example: Sweat glands initiate sweating to reduce body temperature.

Feedback Mechanisms

Negative Feedback

• Definition: The outcome negates or does the opposite of the stimulus.
• Process Example:
  • Stimulus: An increase in body temperature.
  • Receptors: Thermoreceptors.
  • Afferent Signal: Sends information to the brain.
  • Control Center: Brain decides to cool the body down.
  • Efferent Signal: Sent to sweat glands.
  • Effector: Sweating reduces body temperature.
• Example in Cold:
  • Stimulus: A drop in temperature.
  • Effector: Muscles shiver to increase body temperature.

Positive Feedback

• Definition: The outcome amplifies the stimulus.
• Characteristics: Short-term mechanism.
• Process Example:
  • Stimulus: Baby’s head stretching the cervix during labor.
  • Receptors: Stretch receptors in the cervix.
  • Control Center: Brain, particularly the hypothalamus, releases oxytocin.
  • Efferent Signal: Oxytocin signals the uterus to contract.
  • Effector: Uterine contractions push the baby further, amplifying the stimulus.

Summary

• Negative Feedback: Negates or counteracts the initial stimulus.
• Positive Feedback: Amplifies the initial stimulus, typically short-lived.

This summary covers the key concepts of homeostasis and feedback mechanisms, focusing on how the body maintains balance and responds to changes in its environment.