negative feedback

• What should you be able to explain by the end of the video?

  The roles of thyroxine and adrenaline in the body
• What is the purpose of the video for HIA students?

  To explain the roles of thyroxine and adrenaline and how thyroxine levels are controlled
• What are hormones?

  Chemicals released directly into the bloodstream by glands
• What effect do hormones have in the body?

  They cause an effect in specific target organs
• Where are the adrenal glands located?

  At the top of the kidneys
• What hormone do the adrenal glands produce during times of fear or stress?

  Adrenaline
• What is one of the main effects of adrenaline?

  To increase the heart rate
• Why is an increased heart rate important during stress?

  It delivers more oxygen and glucose to the brain and muscles
• What do oxygen and glucose provide for the body during stress?

  They are needed for aerobic respiration
• What is the term scientists use to describe the body's response to fear or stress?

  Fight or flight
• Where is the thyroid gland located?

  At the base of the neck
• What hormone does the thyroid gland release?

  Thyroxine
• What are the two main effects of thyroxine?

  It stimulates the basal metabolic rate and plays a role in growth and development
• What does metabolism refer to?

  The sum of all the reactions in a cell or the body
• How is the level of thyroxine in the blood controlled?

  By negative feedback
• What happens when the thyroxine level falls?

  The pituitary gland releases TSH into the bloodstream
• What does TSH trigger in the thyroid gland?

  It triggers the release of more thyroxine into the blood
• What happens when the thyroxine level increases?

  The brain prevents the pituitary gland from releasing TSH
• What is a negative feedback cycle?

  A process that triggers events to bring a level back to normal
• Can you name other examples of negative feedback cycles in the human body?

  Control of blood glucose and the menstrual cycle
• What are the roles of thyroxine and adrenaline in the body?

  • Thyroxine:
  • Stimulates basal metabolic rate
  • Aids in growth and development
  • Adrenaline:
  • Increases heart rate
  • Prepares the body for fight or flight
• What is the general idea behind negative feedback?

  • Monitors levels in the body
  • Triggers events to increase or decrease hormone levels
  • Maintains homeostasis