Adrenaline & Thyroxine

• Adrenaline prepares you for ''fight or flight"
• Adrenaline is a hormone released by the adrenal glands, which are just above the kidneys
• Adrenaline is released in response to stressful or scary situations - your brain detects fear or stress and sends nervous impulses to the adrenal glands, which respond by secreting adrenaline
• Adrenaline gets the body ready for 'fight of flight' by triggering mechanisms that increase the supply of oxygen and glucose in cells in the brain and muscles. E.g. adrenaline increases heart rate
• Hormone release can be affected by negative feedback
• The body can control the levels of hormones (and other substances) in the blood using negative feedback systems
• When the body detects that the level of a substance has gone above or below the normal level it triggers a response to bring the level back to normal again
• Thyroxine regulates metabolism
• Thyroxine is a hormone released by the thyroid gland, which is in the neck

  
• Thyroxine is made in the thyroid gland from iodine and amino acids
• Thyroxine plays an important role in regulating the basal metabolic rate - the speed at which chemical reactions in the body occur while the body is at rest

  
• Thyroxine is important for loads of processes in the body, such as stimulating protein synthesis for growth and development
• Thyroxine is released in response to thyroid stimulating hormone (TSH), which is released from the pituitary gland

  
• A negative feedback system keeps the amount of thyroxine in the blood at the right level - when the level of thyroxine in the blood is higher than normal, the secretion of TSH from the pituitary gland is inhibited. This reduces the amount of thyroxine released from the thyroid gland, so the level in the blood falls back towards normal