Baroreflex

Baroreflex, also called baroreceptor reflex is the system in the body that regulates blood pressure.

Special nervecells called baroreceptorsare located in the wall of the heart auricles, vena cava, aortic archand carotid sinuses, and are specialized to monitor changes in blood pressure. If the receptors sense a rise in blood pressure, then, through a negative feedback loop, the heartwill slow down to compensate. If they sense a drop in pressure, the heart will speed up.

If blood pressure falls baroreceptor firing rate decreases. Signals from the carotid baroreceptors are sent via the glossopharyngeal nerve(cranial nerveIX). Signals from the aortic baroreceptors travel through the vagus nerve(cranial nerveX) This information is integrated in the medulla oblongata(a part of the brain stem) which sends messages to the heart muscle, the cardiac pacemakerand the arteriolesand veinsof the body.

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

In addition to altering heart rate, baroreflex, through its sympatheticeffector branch, also acts on peripheral vascular resistance (mainly of the arterioles) and venous compliance. It may be responsible for a part of the low frequency component of heart rate variability, the so called Mayer waves.

See also

• Autonomic nervous system
• Baroreceptor
• Blood pressure

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Baroreflex Wikipedia article Baroreflex.