Baroreceptors

Chapter 4 endnote 50, from How Emotions are Made: The Secret Life of the Brain by Lisa Feldman Barrett.
Some context is:

...your body-budgeting regions initiate predictions ​— ​say, that there’s a snake nearby. These predictions prepare you to see and hear a snake. At the same time, these regions predict that your heart rate should increase and your blood vessels should dilate, for instance, in preparation to run. [...] Your arteries contain special cells called baroreceptors.

In this example, it is important to realize that your arteries contain special cells, called baroreceptors, that sense a change in blood pressure and send this information to your brain as prediction error. To prepare your body to run, they might cause your heart to beat faster and harder (increasing cardiac output); they also might cause your blood vessels to widen (to more easily allow blood to make it your limbs).