Given that there is a baroreceptor reflex to regulate blood pressure, how is it possible for blood pressure to remain high in individuals diagnosed with chronic hypertension?

The baroreceptors are no longer responding to the stretch reflex and tension stimulus generated by the increased blood pressure on the walls of the atrial and the heart. Thus they are no longer sensitive to their own responses.

Explanation:

Groups of special receptors in the heart and blood vessels, which are sensitive to fluctuations in blood pressure, and mediate the rise and fall in the blood pressure to relatively constant levels are called baroeceptors.

Thus an elevation in blood pressure, activated the baroreceptors in the blood vessels. With a fraction of a second, of the stimulus of tension on the walls, the receptors send negative feed back loop of sensory signal to the control center in the medulla of the brain.

The brain responded with motor outputs which decreases the heart rates, vasodilation with corresponding reduction in blood pressure; since the pressure of the blood been pumped by the heart has dropped. Conversely, a drop in blood pressure, stimulated less activation of the baroreceptors, and therefore elevation of heart rate with consequent rise in blood pressure to relatively constant level.

Therefore, in chronic hypertension patient the reason for the blood pressure to remain high, despite baroreceptiors is the adpatation of the baroreceptors to the elevated blood pressure. The baroreceptors are no longer responding to the stretch reflex and tension stimulus generated by the increased blood pressure on the walls of the atrial and the heart. Thus they are no longer sensitive to their own responses