Final answer:
Increased blood pressure triggers a reduction in sympathetic outflow to the heart and increased parasympathetic activity, decreasing the heart rate and cardiac output, thus reducing blood pressure.
Step-by-step explanation:
Increased blood pressure stimulates a complex response in the body that involves both the baroreceptors and the autonomic nervous system. When blood pressure rises too high, the baroreceptors that are located in the arch of the aorta and the carotid arteries detect this increase and fire at a higher rate. This triggers a reduction in sympathetic stimulation and an increase in parasympathetic outflow to the heart.
As a result, the heart rate slows down, and the force of cardiac contractions decreases, both of which contribute to lower cardiac output. Simultaneously, the sympathetic stimulation of the peripheral arterioles decreases, causing vasodilation which helps in reducing blood pressure. Thus, the correct answer to the question is B. decreased sympathetic outflow to the heart.