The correct answer is: Baroreceptors in the arteries send a signal to the brain that the blood pressure is low. The brain sends a chemical signal to the heart to increase its rate of pumping. This continues until the baroreceptors sense a normal blood pressure.
A negative feedback loop occurs in the body when something in the body has decreased in function, which could mean high or low, for example blood sugar, body temperature or in this in this case blood pressure. It then creates a feedback loop to tell that part of the body to regulate itself and return the body to a state of homeostasis (which is your optimal internal state). In a negative feedback loop the response of the regulating mechanism is opposite to the output of the event. So if blood pressure is low the negative feedback loop will tell the body to increase the pressure.
A positive feedback will result in more of a product: more prolactin, more contractions, or more clotting platelets.
