Thyroxine Flashcards
All 6 cards in this deck
What does thyroxine control in the body?
Metabolic rate (it also affects protein synthesis, growth and development).
What is metabolic rate?
The rate at which the chemical reactions in the body's cells take place, so the rate at which energy is used.
What is negative feedback?
A control mechanism in which a change away from the normal level triggers a response that brings the level back to normal.
What are the steps of negative feedback control of thyroxine?
e.g. blood thyroxine level falls below normal
- Hypothalamus produces TRH.
- TRH makes the pituitary gland release TSH.
- TSH acts on the thyroid, which releases more thyroxine, returning the level to normal.
What happens when thyroxine levels in the blood are normal or high?
Thyroxine inhibits the release of TRH from the hypothalamus and the production of TSH by the pituitary, so less thyroxine is made.
True or false? If a damaged thyroid gland stops making thyroxine, the level of TSH in the blood will fall.
False. TSH rises, because there is no thyroxine to inhibit TRH and TSH production.