Hormones

What are hormones?

Hormones are chemical messengers the body creates (synthesizes) and sends off (secretes) into the blood stream or sent through extracellular fluid by a cell or gland. For example, hormone A will usually go through the blood and only a few cells will be affected, because each cell has receptors for this specific hormone, they are called target cells. Cells that do not have this receptor cannot be directly affected by hormone A.

There are several kinds of hormone secretion or excretion. Every cell in the body can and does create and secrete hormones, but certain types of cells generally only affect neighboring cells. They will create and release a hormone that travels to near by cells and instruct them what to do, this type of secretion is known as Paracrine action. A cell can also create hormones to effect itself via autocrine action.

There are also two kinds of effects that hormones can have, they can be agonists or antagonists. Agonists are hormones that directly tell a cell what to do. These hormones can vary in potency, meaning they can have a little effect on the cell or a very dramatic effect depending on the potency of these Agonist hormones. Antagonists are hormones that basically block other hormones. The antagonist will attach to a cell receptor and will then stop Agonists from bonding with the cell. Effectively stopping hormones in the system from having any effect on this cell.