The supply of vasomotor drive to individual classes of sympathetic neuron

The vasoconstrictor supplies to different tissues show distinct patterns of ongoing and reflex activity, indicating that they are driven by distinct central pathways. Vasomotor tone depends heavily on connections from the brainstem, so class-specific vasomotor drives have been sought amongst the sympathetic premotor neurons which provide those connections. Premotor neurons of the rostral ventrolateral medulla (subretrofacial nucleus) provide most descending vasomotor drive. Together, they drive the sympathetic supplies to heart, blood vessels and adrenal, but not 'non-cardiovascular' sympathetic responses (sweating, pupil dilatation, piloerection, etc.). Individually, they provide preferential or selective drives to particular classes of 'cardiovascular' sympathetic outflow. Subretrofacial neurons are arranged topographically, forming a neural map of the functional class (target tissue), not the body region, of the driven outflows. It is still unknown whether other premotor cell groups are organised this way. Nor are the premotor pathways to 'non-cardiovascular' sympathetic nerves yet well-defined.