How a beta receptor antagonist causes a decrease in blood pressure?

Answer 1

To understand how beta adrenergic blockade lowers blood pressure, you need to understand a little physiology.

Beta receptors are present in many different places in the body: the heart, the blood vessels, the kidneys, the lungs, the muscles, etc. They perform different tasks in each different place as well, and there are different classes of receptors. For instance, in the heart, the receptors are called beta-1 receptors and they increase the rate of firing of the SA node (chronotropy), increases cardiac conduction velocity (dromotropy) and increase the strength with which the heart beats (inotropy). In the arterioles, the receptors cause dilatation of the vessels and are called beta-2 receptors. In the kidneys, beta-1 receptors increase renin output from the juxtamedullary cells when stimulated. Renin is an enzyme that produces a potent vasocontrictor when it activates the angiotensin cascade.

Now, how does beta antagonism lower blood pressure. First, in the heart, beta blockade causes a slowing of the heart rate and stroke volume, effectively decreasing cardiac output. In the kidneys, beta blockade decreases renin release, which decreases the amount of systemic vasoconstrictors in the body. These two effects cause the blood pressure to decrease over time.