Which group of nerve fibres are least susceptible to LA?
ANS. DErlanger-Gasser classification of nervesFiber typesFunctionAverage fiber diameters (mm)Average conduction velocity (m/s)AaPrimary muscle spindle afferents, motor to skeletal muscle15100 (70-120)ApCutaneous touch and pressure afferents850 (30-70)AyMotor to muscle spindle520(15-30)A5Cutaneous temperature and pain afferents<315(12-30)BSympathetic preganglionic37(3-15)CCutaneous pain afferents sympathetic postganglionic11 (02-2)LA susceptiblity: A delta>gamma>A beta>A alpha>B>CHypoxia: B > A> CPressure: A > B > C
A alpha
A beta
B
C
Nervous System