Target Cell Specificity (Nursing)

00:00 So now let's look at the target cells themselves. Target cells must have specific receptors for the hormone that will bind to them. For example, the ACTH hormone receptors are found only on certain cells of the adrenal cortex. Thyroxine receptors, however, are found on nearly all of the body cells. Target cell activation depends on 3 different factors. First, the blood levels of the hormone; second, the relative number of receptors on the target cell; and third, the affinity or strength of the binding between the receptor and the hormone. The amount of hormone can influence the number of receptors for that hormone. In upregulation, target cells are going to form more receptors in response to low hormone levels. This allows for the cell to be more sensitive to the available hormones. In downregulation, target cells will lose receptors in response to high hormone levels. This is going to desensitize the target cells to prevent them from overreacting to persistently high levels of hormone.