So here we have a pretty straightforward example problem that tells us that damaged endothelial cells release peptide hormones called endothelins, which help to initiate vascular spasm. Considering this, what is the primary effect of endothelins? And we've got these 4 potential answer options down below. Now although we did not talk about endothelins directly in our last lesson video, we can use the information in this problem to solve it. And so we need to highlight the fact that endothelins are going to help initiate vascular spasm, and so whatever the primary effect of endothelin is, it must help initiate vascular spasm. We know from our last lesson video that vascular spasm has to do with the contraction or vasoconstriction of damaged blood vessels. And so notice option B says vasoconstriction, and that is actually going to be the correct answer to this example problem, so we can indicate B is correct.
Now, option A says vasodilation, which is the exact opposite of vasoconstriction, where the blood vessels are going to enlarge their diameter. But that is not going to be the case for vascular spasm, and that's why we can eliminate answer option A. Option C says platelet aggregation, but platelet aggregation is going to be something that occurs in step 2 of hemostasis, which is the platelet plug formation. It is not necessarily something that is going to occur with vascular spasm, and so for that reason, we can eliminate answer option C. And option D says increased blood pressure, and although increased blood pressure may be an indirect result of vasoconstriction, the function of vascular spasm is not necessarily to increase blood pressure, but it is to vasoconstrict. And so for that reason, the primary effect of endothelin is not going to be to increase blood pressure. It is to vasoconstrict. And so option B is the correct answer to this problem, and I'll see you all in our next video.