Thyroxine and adrenaline

• Thyroxine is produced from the thyroid gland, stimulating the basal metabolic rate
• Thyroxine controls the speed at which oxygen and food products react to release energy for the body to use
• Thyroxine plays an important role in growth and development
• Thyroxine levels are controlled by negative feedback, where low levels stimulate the hypothalamus to release TRH, causing the pituitary to release TSH, leading to the thyroid releasing more thyroxine to return blood levels to normal
• Normal thyroxine levels inhibit TRH release from the hypothalamus and TSH release from the pituitary to maintain normal blood levels
• Adrenaline is produced by the adrenal glands in times of fear or stress
• Adrenaline targets vital organs, increases heart rate, and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for 'flight or fight'
• Adrenaline effects include:

  • Increases breathing rate
  • Increases heart rate
  • Converts glycogen to glucose for more energy in muscles
  • Diverts blood away from areas like the digestive system towards the muscles
• Adrenaline is not controlled by negative feedback