Adrenal glands

• secreted from adrenal medulla
• secreted during 'fight or flight', fear and flirt
• adrenaline is a peptide hormone
• receptors adrenaline binds to are on the plasma membrane of target cells
• 1. Adrenaline binds to membrane receptor
  2. Activation of G protein and then enzyme
  3. Activates enzyme and produces cyclic AMP
  4. stimulates glycogen hydrolysis
• If G protein not activated it will be binded to the receptor
• 1. Adrenaline (first messenger) binds to receptors on the cell surface membrane
  2. G protein splits, becomes activated and combines with an inactive enzyme (adenyl cyclase)
  3. Adenyl cyclase converts ATP to cyclic AMP (cAMP - second messenger) cAMP binds to and activates protein kinase
  4. protein kinase activates glycogen phosphorylase kinase which binds to glycogen phosphorylase
  5. glycogen phosphorylase catalyses the breakdown of glycogen into glucose
• • Adrenaline (first messenger)
  • cAMP (second messenger)
• what happens to polysaccharides in the liver cell


  • glycogen broken down into glucose by hydrolysis
• suggest how adrenaline can cause different effects in different target tissues 


  • second messenger can be different
  • activates different enzymes
• outline the hormonal and nervous mechanisms involved in control of heart rate 


  • Adrenaline causes heart rate to increase
  • Heartbeat starts at sino atrial node and releases a wave of depolarisation
  • Medulla Oblongata involved
  • sympathetic nerve increases heart rate
  • High blood pressure detected by stretch receptors
• which hormones secreted by adrenal medulla


  • adrenaline
  • noradrenaline
• Are adrenal glands endocrine or exocrine?


  • endocrine
  • releases adrenaline into the blood
• adrenal cortex


  • zona glomerulosa
  • zona fasciculata
  • zona reticularis
• zona glomerulosa


  • outermost layer, which secretes mineralcorticoids
  • mineralcorticoids control concentrations of sodium and potassium in blood.
  • Also contribute to maintaining blood pressure
• zona fasciculata


  • middle layer, which secretes glucocorticoids
  • help control the metabolism of carbohydrates, fats and proteins in the liver
• zona reticularis 


  • innermost layer, which is thought to secrete precursor molecules that are used to make sex hormones
  • help develop secondary sexual characteristics and regulates the production of gametes
  • can release cortisol if correct enzymes are present
• action of steroid hormones

  1. steroid hormone passes through the cell membrane of the target cell
  2. steroid hormone binds with specific receptor (with a complementary shape)
  3. receptor-steroid hormone complex enters the nucleus of target cell binds to another specific receptor on chromosomal material
  4. binding stimulates production of mRNA, which code for production of proteins
• adrenal cortex hormones


  • uses cholesterol to produce a range of hormones
  • these hormones are steroid base and are able to enter cells by dissolving into cell membrane
  • steroid hormones enter the nucleus and have an effect on the DNA to cause protein synthesis
• adrenal medulla hormones


  • adrenaline is a polar molecule derived from amino acid tyrosine - this means it cannot enter cells through plasma membrane
  • therefore, it must be detected by specialised receptors on plasma membrane of target cells