Adrenaline and Thyroxine

• Adrenaline


  A hormone released by the adrenal glands, which are just above the kidneys
• Adrenaline release


  1. Brain detects fear or stress

  2. Sends nervous impulses to the adrenal glands

  3. Adrenal glands secrete adrenaline
• Adrenaline


  • Gets the body ready for 'fight or flight' by triggering mechanisms that increase the supply of oxygen and glucose to cells in the brain and muscles
  • Increases heart rate
• Negative feedback


  Body's mechanism to control the levels of hormones (and other substances) in the blood
• Thyroxine


  A hormone released by the thyroid gland, which is in the neck
• Thyroxine


  • Plays an important role in regulating the basal metabolic rate
  • Stimulates protein synthesis for growth and development
• Thyroxine release


  1. Thyroxine is released in response to thyroid stimulating hormone (TSH), which is released from the pituitary gland

  2. When the level of thyroxine in the blood is higher than normal, the secretion of TSH from the pituitary gland is inhibited

  3. This reduces the amount of thyroxine released from the thyroid gland, so the level in the blood falls back towards normal
• Thyroxine is made in the thyroid gland from iodine and amino acids