Describe how the levels of thyroxine are controlled in the blood. Use the term negative feedback.
Can't find anything helpful on the web, hopefully someone here can help me :)
Can't find anything helpful on the web, hopefully someone here can help me :)
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In our brain, very close to the medulla is a gland called the hypothalamus, which monitors all the chemicals in our blood. Suppose if the growth hormone is reducing, hypothalamus will stimulate the Pituitary gland, the masters of all the glands(situated below the hypothalamus) to stimulate the growth hormone.
Thyroxin is a hormone produced by the Thyroid. Thyroxin is responsible for metabolism of our body. When the body senses that it does not need thyroxine, it sends a negative feedback to the ever watchful hypothalamus which will reduce or stop the production of thyroxin. And if thyroxin is required by the body, a positive feedback is sent to the hypothalamus which stimulates the pituitary which in turn stimulates the the thyroid gland to reduce the production of thyroxin. This is the simple explanation.
Going into the technical details, when the body needs thyroxin, the hypothalamus stimulates the pituitary by producing TRH (Thyroid Releasing Hormone) and sending it to the anterior lobe of the pituitary. The pituitary in turn releases the TSH (Thyroid Stimulation Hormone). This signal tells the thyroid to stimulate thyroxine. When high leves of thyroxine is produced, the hypothalamus detects it and commands the pituitary to command the thyroid gland to stop or reduce the production of Thyroxin,
Since the production of Thyroxin is stopped because of Thyroxin itself, it is called a negative feedback mechanism.
Hope this helps! Below is a picture of Pituitary and Hypothalamus so that you get a clearer picture.
Thyroxin is a hormone produced by the Thyroid. Thyroxin is responsible for metabolism of our body. When the body senses that it does not need thyroxine, it sends a negative feedback to the ever watchful hypothalamus which will reduce or stop the production of thyroxin. And if thyroxin is required by the body, a positive feedback is sent to the hypothalamus which stimulates the pituitary which in turn stimulates the the thyroid gland to reduce the production of thyroxin. This is the simple explanation.
Going into the technical details, when the body needs thyroxin, the hypothalamus stimulates the pituitary by producing TRH (Thyroid Releasing Hormone) and sending it to the anterior lobe of the pituitary. The pituitary in turn releases the TSH (Thyroid Stimulation Hormone). This signal tells the thyroid to stimulate thyroxine. When high leves of thyroxine is produced, the hypothalamus detects it and commands the pituitary to command the thyroid gland to stop or reduce the production of Thyroxin,
Since the production of Thyroxin is stopped because of Thyroxin itself, it is called a negative feedback mechanism.
Hope this helps! Below is a picture of Pituitary and Hypothalamus so that you get a clearer picture.
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Two links that will help...
http://arbl.cvmbs.colostate.edu/hbooks/p…
http://arbl.cvmbs.colostate.edu/hbooks/p…
http://arbl.cvmbs.colostate.edu/hbooks/p…
http://arbl.cvmbs.colostate.edu/hbooks/p…