Final answer:
Heparin acts as an anticoagulant by opposing the conversion of prothrombin to thrombin, thus interfering with blood clot formation. It does not primarily reduce blood pressure; that action is more characteristic of other substances like ANP.
Step-by-step explanation:
The nurse understands that heparin acts primarily as an anticoagulant, which is a substance that opposes coagulation, the process by which blood forms clots. Heparin works by opposing the conversion of prothrombin (factor II) to thrombin, thereby inhibiting the intrinsic pathway of blood coagulation. It is naturally released from mast cells and can also be found on the surfaces of cells lining the blood vessels. Moreover, in its pharmaceutical form, heparin is used therapeutically to prevent blood clots in at-risk patients, such as those undergoing surgery.
Contrary to the initial assumption, heparin does not primarily act to reduce blood pressure. However, it may indirectly affect blood pressure by preventing clots that can obstruct blood flow. It's important to note, though, that the main effects associated with blood pressure, such as vasodilation and influence on renal functions, are typically attributed to other substances like the atrial natriuretic peptide (ANP), not heparin.