Baroreflex

The baroreflex or baroreceptor reflex is a homeostatic mechanism that maintains blood pressure. It consists of a negative feedback loop in which an elevated blood pressure reflexively lowers the heart rate and thus blood pressure; conversely suppressed low blood pressure to baroreflex, causing heart rate and thus the blood pressure rises again.

This system is based on specialized neurons, known as baroreceptors in the aortic arch and carotid sinus which to measure changes in blood pressure and to report them to the brain stem on. Further changes in blood pressure mediated by the autonomic nervous system. Atrial natriuretic peptide is part of a parallel negative feedback loop as an opponent to the renin -angiotensin system.

Anatomy

Baroreceptors are found in the auricles and the vena cava, but the most sensitive baroreceptors in the carotid sinus and can be found in the aortic arch. The carotid sinus baroreceptors in the innervated by the glossopharyngeal nerve; the baroreceptors in the aortic arch from the vagus nerve. The activity of baroreceptors is transmitted via these nerves to the nucleus of the solitary tract (NTS) of the brainstem.

The NTS sends excitatory glutamatergic fibers to the caudal ventrolateral medulla ( CVLM ) and activates them. The activated CVLM then sends inhibitory GABAergic fibers to the rostral ventral medulla ( RVLM ) and inhibits this. The RVLM is the primary core for control of the sympathetic nervous system; sending excitatory fibers to the preganglionic neurons of the intermediolateral nucleus of the spinal cord. Consequently activate the baroreceptors with high blood pressure the NTS, this activates the CVLM, which in turn inhibits the RVLM and thus inhibits the sympathetic nervous system, which leads to a lowering of blood pressure. Conversely, ensures a low blood pressure for an increase in the tone of the sympathetic nervous system by reducing inhibition of the RVLM.

The NTS also sends excitatory fibers to the nucleus ambiguus, which regulates the parasympathetic nervous system, and lowers so in addition the effects of the sympathetic nervous system in hypertension.

Effect on heart rate variability

The baroreflex is a part of the low frequency component of heart rate variability, at about 0.1 Hz

Credentials

• Berne, Robert M., Levy, Matthew N.: Cardiovascular Physiology. Mosby, Philadelphia, PA 2001, ISBN 0-323-01127-6.
• Boron, Walter F., Boulpaep, Emile L.: Medical Physiology: A Cellular and Molecular Approach. Elsevier / Saunders, Philadelphia, PA 2005, ISBN 1-4160-2328-3.

• Cardiovascular physiology