Endocrine System

• Homeostasis


  Keeping a stable internal environment
• Insulin


  Hormone that decreases blood glucose levels
• Stimulus-Response Model

  1. Internal environment detects change

  2. Stimulus is sensed by receptors

  3. Receptors send a message to control centre

  4. Control centre processes message

  5. Effectors carry out the response
• When blood glucose levels rise above normal

  Pancreas secretes insulin
• When blood glucose levels are too low

  Pancreas releases glucagon
• Oxytocin increases contractions to induce labour and birth and release of milk from breast after birth
• Cortisol maintains blood pressure, immune function and anti-inflammatory processes
• Negative feedback reduces the response to keep within a stable/normal range
• Blood sugar levels are controlled by two hormones: insulin and glucagon
• Insulin is released by beta cells in the pancreas
• Glucagon is released by alpha cells in the pancreas
• Both insulin and glucagon are produced by the pancreas
• High blood glucose levels stimulate the release of insulin
• Low blood glucose levels stimulate the release of glucagon
• Negative feedback is a counteracting response to maintain blood glucose levels
• Insulin


  A hormone that lowers blood glucose levels by promoting glucose uptake and storage.
• Glucagon


  A hormone that raises blood glucose levels by stimulating the liver to release glucose.
• Negative feedback loop


  A self-regulating mechanism that reverses changes to maintain homeostasis.
• Negative feedback loop path

  1. Stimulus
  2. Receptors
  3. Effectors
  4. Response
• The liver uses stored glycogen and turns it into glucose