ROLE OF HORMONES IN
HOMEOSTASIS -
When the secretion of hormones is under the control of factors or other hormones it is called feedback control. lation of secretion of thyroxine from the thyroid gland is an example of such feedback control mechanism.
Feedback control is of two types:
Positive feedback control:-
If the level of thyroxine is less than normal limits in the blood, thyroxine level stimulates the hypothalamus to secrete more of TRH which results in increased secretion of TSH which in turn stimulates increased secretion of thyroxine.
Such regulatory effect is called positive feedback control.
Negative feedback
control :
The thyrotropin releasing hormone (TRH) from the hypothalamus
stimulates the anterior lobe of the
pituitary gland to secrete the thyroid stimulating hormone (TSH). The TSH in turn stimulates the
thyroid gland to secrete thyroxine. A high amount of thyroxine in the blood exerts an inhibitory effect
on hypothalamus in such a way that less of TRH and TSH is produced respectively. This eventually results in a decreased production of thyroxine. This is called negative feedback control.
