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What are the baroreceptors?
Baroreceptors are spray-type nerve endings in the walls of blood vessels and heart that are stimulated by the absolute level of, and changes in, arterial pressure.
They are extremely abundant in the wall of carotid sinus and aortic arch. The primary site of termination of baroreceptor afferent fibers is the NTS.
What is significance of baroreceptors?
The function of the baroreceptors is to maintain systemic blood pressure at a relatively constant level, especially during a change in body position.
Intact baroreceptors are extremely effective in preventing rapid changes in blood pressure from moment to moment or hour to hour, but because of their adaptability to prolonged changes of blood pressure (>2 or 3 days), the system is incapable of long-term regulation of arterial pressure.
Stretching of the baroreceptors as a result of increased blood pressure causes an increase in the activity of the vagal nerve by projection to the nucleus ambiguus.
It also causes inhibition of the sympathetic outflow from the RVLM, ultimately leading to decreased heart rate and blood pressure.
Conversely, decreased blood pressure results in decreased signal output from the baroreceptors, leading to disinhibition of the central sympathetic control sites and decreased parasympathetic activity.
The final effect is an increase in blood pressure.
