Negative feedback

• Hormones are chemical messengers sent in the blood
• Adrenaline - 'fight' or 'flight'

  • Produced by Adrenal gland
• Fight or Flight

  1. Adrenaline binds to specific receptors in the heart
  2. This causes the heart to contract more = increases heart rate and blood pressure
  3. This increases blood flow to muscles = more oxygen and glucose to muscles = more respiration
  4. Adrenaline also binds to the liver to break down glycogen to release glucose.
  5. This means there is more glucose in the blood to get to the cells and either 'fight' or 'flight'
• In a stressful situation, a nervous impulse is sent to the adrenal glands to release adrenaline.
• Negative feedback - When the hypothalamus detects a change in internal conditions, it triggers a response to bring the level back to normal
• Examples of negative feedback

  • Body is too hot = Begin to sweat to cool down
  • Body is too cold = Begin to shiver to warm up
• Thyroxine regulates metabolism

  • Released by thyroid gland
• Metabolism = The speed at which chemical reactions occur in your body.
• Thyroxine is released based of the Thyroid Stimulating Hormone (TSH) which is released from the pituitary gland.
• When the level of thyroxine in the blood is too high, the secretion of TSH for the pituitary gland is inhibited, reducing the amount of thyroxine produced.