98o 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY 11 



TABLE I . Spinal Cord Segments Giving Rise 

 to Autonomic Outflows 



Species 



Thoracolumbar 

 Outflow 



Sacral Outflow 



Man (341, 385) Ti-L2[Li or L'j^ S3[S2]-S4fS5] 



Monkey (385, Ti or T2 — L3 or Si — S2[S3] 



387, 449) L4[L5J 



Dog (258, 311, T2[Ti] - S2[Si] - S3 



383) L4[L5, L6; 



Cat (258,385) Ti[T2] - L4[L5J S2[Si] - S3[S2] 



Rabbit (258) Ti - L5 



Figures in parentheses are reference numbers. 

 Rare variants in brackets. 



sion of the autonomic transmitters appears in Chapter 

 \'II by von Euler in this work. 



GENERAL ORGANIZATION OF PERIPHERAL 

 AUTONOMIC NERVOUS SYSTEM 



Sympathetic Division 



The preganglionic fibers arise from ner\e cells in 

 the intermediolateral column of the thoracic and 

 upper lumbar segments and leave the spinal cord 

 via the ventral roots to run through the white com - 

 municating rami to the trunk ganglia or to the pre- 

 vertebral ganglia. The upper limit of the preganglionic 

 outflow in man and various animals is Ti, but the 

 caudal extension is more variable (table i). Generally 

 the spinal centers for the sympathetic innervation of 

 structures sucli as the eye, the heart and the blood 

 vessels of the hand are located in two or more seg- 

 ments (table 2). \'ariations between aniinals of the 

 same species and asymmetry often exist and the pre- 

 ganglionic outflow can be markedly inconstant, es- 

 pecially in the lumbar region, as shown for the sudo- 

 motor and pilomotor fibers to the lower extremities of 

 man (202, 350). 



On the basis of anatomical studies, it has been sug- 

 gested that nerve cells in the intermediomedial part 

 of the spinal cord also give rise to preganglionic fibers 

 which run up into the cervical and down into the 

 lower lumbar region (cf. 317). There is, however, no 

 physiological evidence for an autonomic outflow from 

 these parts of the spinal cord, and the anatomical evi- 

 dence is of speculative character only. 



It has been claimed that autonomic efferent fibers 

 also emerge through the dorsal roots. The evidence 

 is mainly based on the well-known oljservations of 

 vasodilation mediated by dorsal root fibers (cf. 17, 



T.\BLE 2 . Spinal Cord Segments Providing Sympathetic 

 Innervation to I 'arious Regions 



Monkey Dog Cat 



Eye T1-T4 (166) T1-T3 (258, T1-T3 (258) 



C8-T3 (320) 320:) [C8]Ti-T2 



(320) 

 Ti-T4[T5] 

 (166) 

 Submax- T1-T5 (258) T1-T5 (258) 



illary 

 gland 

 Heart T2-T6 (373) T1-T5 (258) 



T2-T5 (45, 69) 

 Bronchi T1-T4 (105) 



Upper ex- T4-T8 (386) 



treinity 

 Lower ex- T12-L3 (386) Ti 1-1.41386) 



tremity 

 Forefoot T4-T10 (166 1 T4[T3j-T9- 



fTioj (166, 

 257. 259. 260) 

 Hind foot T10-L3 (i66i Ti2[Tii]-L4 



(166, 257, 259, 

 260, 336) 



Figures in parentheses are reference numbers. 

 Rare variants in brackets. 



155) and on tiie demonstration of intact nerve fibers '-'^ 

 in the central stump after section of dorsal roots (cf. 



384, 448). However, the anatomical evidence has 

 been found to be unreliable as the obser\ed unde- 

 generated fibers may be regenerating axons from the 

 distal stump (209, 398, 438). Moreover, the ratio be^ 

 tween the cells in the spinal ganglion and the fibers^ 

 in the dorsal root seems to be 1:1 (113, 214), and no 

 convincing neurohistological or physiological e\ idence 

 has been brought forth that there are synaptic struc- 

 tures in these ganglia. The physiological evidence for 

 the existence of efferent dorsal root vasodilators has 

 been severeh criticized by several investigators (cf. 



1 52). Recent reinvestigation of the problem by Folkow I 

 et al. (155) has made the existence of such fibers .seem / 

 highly improl:)able. 



The distribution and anatomical variations of the 

 white and grey rami and their fiber components have 

 been studied by several investigators (96, 311, 341, 



385, 387) whose results on the whole confirmed the 

 observations of Langley. The existence of some post- 

 ganglionic pilomotor fibers in lumbar white rami 

 was already demonstrated by Langley (263). How- 

 ever, some findings of importance for physiological 

 research work have complicated the picture. Accord- 

 ing to Hare (190) the gre\" rami in some instances 



