SB7b-Hormonal control of meatbolic rate

• What are the effects of adrenalin on the body?

  • Fast heatbeat
  • Increased blood pressure by constricting blood vessels
  • More blood is sent to muscles by dilating other blood vessels
  • Conversion of glycogen to glucose in liver cells, increasing blood glucose levels
• Adrenalin

  Adrenalin is a hormone that is released from the adrenal glands in response to sudden stress. It brings out the 'fight or flight' response
• Explain how adrenalin is useful for preparing skeletal muscles for fight or flight

  • The heart beating faster means that more oxygen is carried around the body faster, because this allows faster respiration in muscle cells, energy is released for cell contractions to be faster.
  • The blood glucose concentration also increases, making more glucose available for respiration in muscle cells
  • Increased blood flow to muscles supplies oxygen and minerals for faster respiration
• Thyroxine

  Thyroxine is a hormone that controls metabolic rate
• What is metabolic rate?

  The rate at which cells respire, and is measured at the rate of energy transfers in the body
• The production of thyroxine is an example of negative feedback
• Explain how the production of thyroxine is controlled by negative feedback

  • When the concentration of thyroxine in the blood gets too low, this stimulates a corrective mechanism
  • The hypothalamus secretes more TRH
  • Which causes the pituitary to produce more TSH
  • As a result, the thyroid produces more thyroxine
  • If the thyroxine concentration gets too high, the TRH production by the hypothalamus is inhibited so less thyroxine is produced