endocrine communication

• • There are 2 types of gland - exocrine and endocrine
• endocrine glands


  • endocrine glands secrete hormones directly into the bloodstream
• exocrine glands


  • exocrine glands secrete hormones into a duct (tube) which carries the hormone to a specific part of the body e.g salivary glands
• Hormones bring about changes in target cells in 2 ways


  • Binding to receptors on a cell surface membrane of target cells
  • Entering target cells and the nucleus and then having a direct effect on the DNA
• steroid hormones are lipid soluble


  • pass through phospholipid bilayer because they're non polar molecules
  • enter target cells
• peptide hormones are small but charged


  • bind to receptors on the surface of target cells
  • charged/ polar so they cant cross phospholipid bilayer
• examples of peptide hormones


  • adrenaline
  • insulin
  • glucagon
• examples of steroid hormones


  • oestrogen
  • progesterone
• The receptor for steroid hormones is inside the cell. Once bound to their receptor, steroid hormones form a transcription factor which is able to switch genes on or off.