Negative feedback

• What is the role of hormones in the body?

  They are chemicals released into the bloodstream
• Where are the adrenal glands located?

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

  Adrenaline
• What is one main effect of adrenaline?

  Increases heart rate
• Why does increased heart rate benefit the body during stress?

  More oxygen and glucose are delivered
• What do oxygen and glucose provide for the body?

  They are needed for aerobic respiration
• What is the term used 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?

  Stimulates metabolic rate and growth
• What does metabolism refer to?

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

  By negative feedback
• What monitors the level of thyroxine in the blood?

  The brain
• What does the pituitary gland release when thyroxine levels fall?

  TSH (Thyroid Stimulating Hormone)
• What does TSH trigger the thyroid gland to do?

  Release more thyroxine
• What happens when thyroxine levels increase?

  TSH release is prevented
• What is a negative feedback cycle?

  Events triggered to maintain balance
• Can you name other negative feedback cycles in the body?

  Blood glucose control and menstrual cycle
• What are the roles of thyroxine and adrenaline in the body?

  • Thyroxine: Stimulates metabolic rate and growth
  • Adrenaline: Increases heart rate and prepares for fight or flight
• Describe the process of negative feedback for thyroxine levels.

  1. Thyroxine levels fall
  2. Brain signals pituitary gland
  3. Pituitary releases TSH
  4. TSH stimulates thyroid to release thyroxine
  5. Thyroxine levels rise
  6. Brain detects rise and stops TSH release