Tuesday, January 31, 2012
The arterial baroreceptors are nerve ending receptors (located in the carotid sinuses and the aortic arch) which react to changes in blood pressure. The reflexes that homeostatically regulate arterial pressure originate primarily with this arterial receptors that respond to changes in pressure. High in the neck, each of the two major vessels supplying the head, the common carotid arteries, divides into two smaller arteries. At this division, the wall of the artery is thinner than usual and contains a large number of branching, vinelike nerve endings. This portion of the artery is called the carotid sinus (the term "sinus" denotes a recess, space, or dilated channel). Its nerve endings are highly sensitive to stretch or distortion. Since the degree of wall stretching is directly related to the pressure within the artery, the carotid sinuses serve as pressure receptors, or baroreceptors. An area functionally similar to the carotid sinuses is found in the arch of the aorta and is termed the aortic arch baroreceptor. The two carotid sinuses and the aortic arch baroreceptor constitute the arterial baroreceptors. Afferent neurons from them travel to the brainstem and provide input to the neurons of cardiovascular control centers there.