Neuroanatomy of Central Cardiovascular Control. Nucleus Tractus Solitarii: Afferent and Efferent Neuronal Connections in Relation to the Baroreceptor Reflex Arc

Abstract

In this chapter, the neuroanatomy of the baroreceptor reflex arc is reviewed and relevant new data are presented. The baroreceptor reflex arc consists of a multisynaptic neuronal chain. Primary neurones have perikarya in the nodose ganglion, and they connect the peripheral baroreceptor sites with the nucleus tractus solitarii (NTS) via fibres in the 9th and 10th cranial nerves. The first synapse in the baroreceptor reflex arc and also the origin of the secondary neurones are located in the caudal and partly in the commissural parts of the NTS. Neuroanatomical topography of the NTS and neighboring medullary nuclei in the rat is presented and detailed. The fibres of the secondary neurones terminate in various medullary nuclei and probably reach—directly or by multisynaptic pathways—the higher regions that may modulate the baroreceptor reflex arc. The chapter presents a discussion on the possible site of these modulatory centers in the hypothalamus and in the brain stem and of the loop of the descending fibres from these regions to the medullary and spinal baroreceptor neurones. The efferent preganglionic neurones of the baroreceptor reflex arc are located in the medulla oblongata and in the intermedio-lateral nucleus of the spinal cord. The chapter outlines the possible interrelationship between the modulatory biogenic amine-containing neurones and the baroreceptor reflex arc.