I I 92 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



ture regulation is related to postnatal rather than 

 total postconceptive age, and rises rapidly after birth 

 (37a). It has been proposed that the improvement 

 in temperature regulation is correlated w itli the proc- 

 ess of nnelination of ner\e fibers in the hypothalamus 

 (38). 



Phylogeni'sis of Central Temjiniituir Regulation 



The diflferent thermoregulatory effector mecha- 

 nisms vary in ciuantitati\e importance among dififer- 

 ent animal species. Piloerection is important in furred 

 animals, and feather erection in birds. Sweating is 

 less important in furred animals than in man, often 

 being confined in the former to the foot pads. Such 

 animals use panting plus salivation to lose heat by 

 water evaporation. 



Central nervous thermodetectors have been demon- 

 strated in birds (177) and e\en in the turtle, a poikilo- 

 thermic animal (175, 176). 



Regulation in Intact Alan 



Although the existence of hypothalamic thermo- 

 ceptive structures has not been directh proved in 

 man, it is reasonable to assume that they do exist. 

 The effect of bilateral frontal lobotomy indicates 

 that the frontal lobe cortex does not play a prominent 

 role in human temperature regulation. Mechanical 

 stimulation of the hypothalamic region may cause 

 transient hyperthermia (23, 66, 144). Tumors which 

 destroy large parts of the hypothalamus may (57, 213) 

 or may not (66) produce prominent disturbances of 

 tcinperature regulation, with hyper- (3) or hypo- 

 thermia. As such lesions are never strictly defined, and 

 often are accompanied ijy destruction of other regions 

 such as the hypophysis, the result is difhcult to evalu- 

 ate. The main trend of observations, however, strongly 

 suggests (57) that hypothalamic structures are of 

 similar importance for coordination of temperature 

 regulation in man as in animals. 



INTER.-^CTION OF PERIFHER.AL .AND CENTR.AL 

 F.'\CTORS IN TEMPERATURE REGULATION 



The relative importance of surface thermoreceptors 

 in comparison with central nervous thermodetectors 

 in different homeothermic species has not been prop- 

 erly evaluated, but the principle of operation of such 

 a double set of thermoceptive structures .seems to be 

 fundamental. The central thermodetectors reflect 



central ijlood temperature, being independent of 

 thermoregulatory effector responses, while surface 

 thermoreceptors reflect peripheral blood and cutane- 

 ous temperatures, beina; dependent on changes in 



TEMP 



374 



'C 372 



370 



36-8 



, RECTAL 



.-""V 



H.E. 



k9 cal 



10 



30 



4o 



SO 



60 



70 



FIG. 22. Effect of external heating of one arm on rectal and 

 oral temperatures, and heat elimination (H.E., index of cuta 

 neous blood flow) from the other hand in normal man. .\t. the 

 10th min. external heating began and was slowly intensified. 

 There is significant correlation between the rate of oral tem- 

 perature rise and rate of heat-elimination increase, but no 

 significant correlation between rectal temperature and heat 

 elimination. [From Gerbrandy el at. (78).] 



725 ml saline 

 45-4 °C 



376 



10 20 



MINUTES 



FIG. 23. Effect of rapid intravenous infusion of hot saline on 

 rectal and oral temperatures and heat elimination from the 

 hand {H.E., index of cutaneous blood Bow) in normal man. 

 Inlenupled tines: Mean control lesel. Dotted tines: Mean reaction 

 level. There is a significant correlation between oral tempera- 

 ture rise (amplitude times duration) and excess heat eliminated, 

 but no correlation with rectal temperature. [From Gerbrandy 

 etat. (78).] 



