Endocrine System and Feedback Loops

Components of Feedback Loops

• Stimulus
  • A change in a body condition.
• Production Cell
  • An endocrine cell that produces a hormone in response to a stimulus.
• Hormone
  • The signaling chemical.
• Target Cell
  • A cell receptive to the hormone.
• Action
  • What the target cell does when affected by the hormone.
• Response
  • The overall change in the controlled body condition due to the feedback loop.

Example: Erythropoietin (EPO) and Blood Oxygen Regulation

• Stimulus
  • Low blood oxygen levels.
• Production Cell
  • Kidney cells secrete erythropoietin (EPO).
• Hormone
  • Erythropoietin (EPO).
• Target Cell
  • Precursor erythrocytes in hemopoietic tissue.
• Action
  • EPO causes precursor erythrocytes to differentiate and proliferate.
• Response
  • Increased numbers of mature red blood cells are released into the blood.
  • Blood's oxygen carrying capacity increases.
  • Blood oxygen level is restored to normal.