Baroreceptor

Baroreceptors (or baroceptors) in the human body detect the pressure of blood flowing though them, and can send messages to the central nervous system to increase or decrease total peripheral resistance and cardiac output.

There is a baroreceptor present in the arch of the aorta, and one in each of the carotid sinuses in the left and right internal carotid artery.

Baroreceptors act to maintain mean arterial blood pressure to ensure that tissues are always being given the right amount of blood.

If blood pressure falls, such as in hypovolaemic shock, baroreceptors stop firing as they are not being stretched as much. This information is integrated in the medulla oblongata. This sends messages to the heart muscle, the cardiac pacemaker and the arterioles and veins of the body.

The heart will begin to beat faster, and contract more forcefully. This increases cardiac output. The arterioles and veins contract (vasocontriction and venoconstriction), this increases total peripherial resistance. Both these things serve to bring mean arterial blood pressure back to normal.

Baroreceptors work by detecting the amount of stretch. The more the baroreceptor walls are stretched, the more frequently they generate action potentials. The carotid baroreceptors have a lower threshold for firing, so these are generally the dominant baroreceptors.

Signals from the carotid baroreceptors are sent via the glossopharyngeal nerve (cranial nerve IX). Signals from the aortic baroreceptors travel through the vagus nerve.