Cardiovascular Control in Spinal Man

The sympathetic outflow emerges from the thoracic and upper lumbar seg­ ments of the spinal cord and in patients with high spinal cord lesions is dissociated from cerebral regulation. This results in disordered cardiovascular control that is influenced by the level and completeness of the lesion, in addition to other factors such as hormones that directly alter cardiovascular function or indirectly influence it by changing renal function or intravascular volume. In this review emphasis is placed on patients with complete cervical spinal cord transection above the sympathetic outflow; they form a human physiological model, in whom the afferent, central, and vagal efferent com­ ponents of the baroreflex arc are intact, but where the spinal and peripheral sympathetic nervous system is isolated (Figure 1). Other than a section on recently injured tetraplegics in spinal shock, all descriptions refer to chroni­ cally injured tetraplegics (synonomous with quadriplegics).