THEEMAL PHENOMENA OF THE BODY 



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anything which heats the skin causes a reflex dilation of its 

 arterioles and lessens the supply of blood to internal organs. 

 The secretion of perspiration is also under the control 

 of the nervous system. The sweat glands, like the salivary 

 glands, receive nerves, and secrete only in response to their 

 stimulation. When the nerves going to the sweat glands of 

 any region are injured, exposure of these glands to external 



Nerve Endings affected 

 by Warmth 



FIG. 89. Diagram of the cutaneous reflexes of temperature regulation 



Showing the epidermis, blood vessels of the dermis, a sweat gland, and the 

 nervous mechanism governing blood vessels and sweat glands 



warmth produces no perspiration; stimulation of their nerves, 

 however, produces a copious secretion. 



24. The skeletal muscles the main organs in the regulation 

 of heat production. The third mechanism of heat regulation 

 is that whereby the amount of heat produced is increased 

 as it is needed. The main organs here concerned are the 

 skeletal muscles. As the afferent impulses started in the 

 skin by the stimulation of cold become stronger, they ulti- 

 mately stimulate reflexly the skeletal muscles to contraction, 

 and so to the production of heat. This contraction does not 



