MEPX
Chapter 12 of 14All chapters
  1. 1How the body is organised
  2. 2Cells and tissues
  3. 3The skeleton
  4. 4Muscles
  5. 5Heart and circulation
  6. 6Blood
  7. 7Lungs and breathing
  8. 8Digestion
  9. 9Kidneys and liver
  10. 10The nervous system
  11. 11The brain
  12. 12Hormones
  13. 13Skin and senses
  14. 14The immune system

Chapter 12 of 14

Hormones

Slow messages through the blood.

The endocrine system

Glands release hormones into the blood to act on distant organs. Nerves are fast and precise; hormones are slower and broader, and the two systems work together.

  • Insulin, made in the pancreas, lets cells take in glucose and so regulates blood sugar.
  • Adrenaline raises heart rate and releases energy for immediate effort.

Feedback loops

Most hormones are controlled by negative feedback: the effect they produce reduces the signal that released them. That is how the body holds a level steady without a controller watching it.