negative feedback

• What are hormones?

  Chemicals released directly into the bloodstream by glands
• What effect do hormones have on 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 does an increased heart rate benefit the body during stress?

  It delivers more oxygen and glucose to the brain and muscles
• 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?

  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 monitors the level of thyroxine in the blood?

  The brain
• What happens when the thyroxine level falls?

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

  It triggers the thyroid gland to release more thyroxine
• What is a negative feedback cycle?

  A process that triggers events to increase or decrease hormone levels
• What occurs when the thyroxine level increases?

  The brain prevents the pituitary gland from releasing TSH
• 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 and aids in growth and development.
  • Adrenaline increases heart rate and prepares the body for fight or flight.
• What is the general idea behind negative feedback?

  • Monitored levels trigger responses to maintain balance.
  • If a hormone level falls, mechanisms are activated to increase it, and vice versa.
• What should students focus on for their exams regarding the endocrine system?

  • The adrenal glands
  • The thyroid gland
  • Negative feedback mechanisms