The sympathetic nervous system is also incompletely developed at birth. The human heart is innervated early in development. In some species beta adrenergic influence on the fetal heart is small early in gestation. Stressful conditions, however, such as hemorrhage and hypoxemia, result in a definite increase in beta adrenergic stimulation ( Heymann, 1984). Alpha adrenergic responses make a progressive contribution to vascular tone throughout fetal life. It has been suggested that the norepinephrine from the adrenal and fetal paraaortic bodies (extra adrenal chrornaffin cells) supports vascular tone until the sympathetic nervous system takes over ( Lewis, 1975). Adrenergic receptors, though functional at gestation, increase in concentration and responsiveness in early infancy ( Heymann, 1984). Recent evidence suggests that diminished norepinephrineinduced lipolysis in the first year of life is due, in part, to enhanced alpha inhibition of lipolysis in infants ( Marcus, Karpe, Bolme, Sonnenfeld, & Arner, 1987). This limitation of lipolysis may have a protective effect during early life. The cold pressor and tilt table responses of neonates resemble those of the adult ( Loggie & Van Maaen, 1972).
Akerstedt T., Gillberg M., Hjemdahl P., Sigurdson K., Gustavsson I., Daleskog M., & Pollare T. ( 1983). "Comparison of urinary and plasma catecholamine responses to mental stress". Acta Physiologica Scandinavica, 117, 19-26.
Arner P., Engfeldt P., & Nowak J. ( 1981). "In vivo observation on the lipolytic effect of noradrenaline during therapeutic fasting". Journal of Clinical Endocrinology and Metabolism, 53, 1207-1212.
Arnetz B. B., & Fjellner B. ( 1986). "Psychological predictors of neuro-endocrine responses to mental stress". Journal of Psychosomatic Research, 30( 3), 297-305.
Baum D., & Porte, D. ( 1971). "Alpha-adrenergic inhibition of immunoreactive insulin release during deep hypothermia". American Journal of Physiology, 221, 303-311.
Cannon W. B. ( 1939). The wisdom of the body. New York: Norton.
Carruthers M., & Taggart P. ( 1973). "Vagotonicity of violence; biochemical and cardiac responses to violent films and television programmes". British Medical Journal, 3, 384-389.
Clutter W. E., Bier D. M., Shah S. D., & Cryer P. E. ( 1980). "Epinephrine plasma metabolic clearance rates and physiologic thresholds for metabolic and hemodynamic actions in man". Journal of Clinical Investigation, 66, 94-101.
Cryer P. E., Haymond N. W., Santiago J. V., & Shah S. D. ( 1976). "Norepinephrine and epinephrine release and adrenergic mediation of smoking-associated hemodynamic and metabolic events". New England Journal of Medicine, 295, 573-577.
Depocas F. ( 1961). "Biochemical changes in exposure and acclimation to cold environments". British Medical Bulletin, 17, 25-31.
DiBona G. F. ( 1982). "Neural mechanisms in body fluid homeostasis". Federal Proceedings, 45, 2871-2884.