<prompt> Physiological effects of spinal anesthesia are due to blockage of:Sympathetic nerve rootsAfferent motor nervesSensory fibresDifferent motor nerves  <response>: Most of the physiological effects of spinal anesthesia are a consequence of the sympathetic blockade produced by local anesthetic block of the sympathetic fibers in the spinal nerve roots. Preganglionic sympathetic fibers are more sensitive to low concentrations of local anesthetic. Clinically, the most impoant effects of sympathetic blockade during spinal anesthesia are on the cardiovascular system. Ref: Catterall W.A., Mackie K. 2011. Chapter 20. Local Anesthetics. In L.L. Brunton, B.A. Chabner, B.C. Knollmann Eds, Goodman Gilmans The Pharmacological Basis of Therapeutics, 12e. 