Hormonal Communication

• Basic Info

  Exocrine

  • Ducted
  • Releases sweat, saliva, enzymes, etc not into blood

  Endocrine

  • Ductless
  • Secretes hormones directly to blood

  Hormones

  • Secreted from ‘ductless’ endocrine glands directly to blood
  • They effect target cells due to its specific complimentary-shaped receptors
  • Short life span; hydrolysed by enzymes in cells, or excreted in urine
  • So can be turned off quickly; Insulin lasts 10-15min + adrenaline 1-3min
  • Messenger to carry signal from endocrine gland to target cell/tissue/organ
  • Concentrations are low; µg/cm3 + secretion rates vary; few µg/mg a day (adrenaline exception)
  • Small molecules, 2 groups:
  • Protein hormones
  • Insoluble
  • Bind to surface receptor
  • Release second messenger in cell
  • E.g. Adrenaline
  • Steroid based hormones
  • Bind to intracellular receptor
  • Direct effect on DNA
  • Arrive in blood on carrier proteins; liposomes/lipoproteins
  • E.g. Testosterone