Stimulus-response model

• Factors in the environment cause an increase or decrease in the variables and homeostatic responses work in the opposite way to reverse the changes
• Elements of the model

  • Stimulus
  • Receptor
  • Transmission
  • Effector
  • Response
  • Feedback
• Stimulus


  A variable factor in the internal or external environment that can be detected by the organism
• Receptor


  Cells or tissues that can detect a change in the external or internal environment (a stimulus)
• Transmission

  The relay of the information via nerves and/or hormones to an effector
• Effector


  Usually a gland or muscle that brings about a response after receiving the information
• Response

  An action which occurs due to the initial stimulus
• Feedback


  The impact of the response on the initial stimulus; may be positive or negative
• Negative feedback occurs when the response diminishes or reverses the original stimulus
• Positive feedback occurs when the response reinforces or brings about an increase in the initial stimulus 
• Examples of negative feedback  would be when an increase in exercise raises metabolic activity, giving rise to an increase in blood temperature.  The increase in temperature is detected by receptors in tissues and the end result is that homeostatic responses by effectors reverse the original stimulus to lower the temperature
• Stimulus → Receptor (secretory glands) → Control centre (Gland) → Effector (hormone) → Response