role of the central nervous system in cardiovascular control. Possibly as a consequence of Folkow's interest in the interplay between body and mind he became interested in central nervous control of the cardiovascular system. He particularly pointed to the role of the defence-alarm reaction (the fight-or-flight response) in everyday blood-pressure control. His opinion was that individuals with a tendency to react more strongly with this response tend to develop higher blood pressure, since they more often get blood pressure elevation in response to common stressors. Even though the kidney is important for blood pressure control, he viewed it as subordinate to the brain. The function of the sympathetic nerve terminals. The sympathetic nervous system has a central role in blood pressure control. It thus attracted Folkow's attention early on, in particular following the mapping of this system. Combining quantification of the density of adrenergic varicosities in the vascular wall with estimates of noradrenaline release indicated that on average only a few per cent of the transmitter content of a synaptic vesicle was released from a given nerve terminal by an action potential in the nerve. It has since been found that transmitter release from a varicosity is intermittent, but whether all or only part of the vesicle's contents is released is still a matter of debate. The physiology of aging. Partly because of his contacts with the professor of geriatrics in Gothenburg, Alvar Svanborg, Folkow acquired an interest for the implications of physiological aging in cardiovascular control. This collaboration resulted in a major review article in this field. Textbook Circulation This textbook was written by Folkow in collaboration with Eric Neil. It is a thorough description of the essential concepts in this area, and large parts of it remain relevant even today, although for obvious reasons more modern aspects are lacking. A follow-up was planned in the eighties in collaboration with Paul Korner, but due to differences in opinion on several aspects Folkow withdrew from the collaboration to save their friendship. References Swedish physiologists 1921 births 2012 deaths Academic staff of the University of Gothenburg Members of the Royal Swedish Academy of Sciences