224 /• /. Christian 



greater rise in blood pressure than epinephrine because it increases overall 

 peripheral resistance, largely by constricting the vasculature of the muscles 

 as well as of the skin (Bell et al., 1950) . Epinephrine produces a greater 

 constriction of the vasculature of the skin, but dilates the vessels of the 

 skeletal muscles and increases the cardiac output by increasing the rate and 

 strength of the heart beat. The effects of norepinephrine on cardiac output 

 are variable. Both of these amines decrease the formation of urine, produce 

 relaxation of the gut by inhibition of its smooth muscle, produce splenic 

 contraction, dilate the bronchi, inhibit the bladder, and produce pupillary 

 dilatation (Bell et al., 19501 . Both produce a rise in blood sugar but, as we 

 have mentioned, epinephrine produces a greater rise than norepinephrine. 

 The rise in blood sugar and subsequent glucosuria result from the mobiliza- 

 tion of glucose from the readily available stores in the liver, and secondarily 

 from the muscles. The immediate effect of epinephrine is to release glucose 

 from the available stores of liver glycogen ; therefore the magnitude of the 

 resulting hyperglycemia depends on the amount of glycogen in the liver 

 (Hartman and Brownell, (1949). The eventual effect of epinephrine, after 

 an initial depletion of liver and muscle glycogen, is to shift carbohydrate 

 from the muscles to the liver, as the uptake of glucose by muscle is de- 

 pressed and it is well known that lactic acid derived from muscle glycogen 

 is used by the liver to synthesize glycogen. 



The actions of these hormones are the classic preparations for "fight or 

 flight" in response to emergency situations (Cannon, 1915, 1932) . The com- 

 bined activity of epinephrine and norepinephrine ensure adequate blood 

 and glucose to the muscles, increased oxygenation, and adequate blood 

 flow. An increased supply of oxygen to the tissues is ensured by an increase 

 in respiratory rate, bronchial dilatation, and contraction of the splenic 

 capsule with release of stored red blood cells into the circulation. Other 

 activities, unneeded in an emergency, are suppressed. The adrenal medulla 

 and sympathetic nervous system respond to cold, fear, rage, trauma, pain, 

 blood loss, anoxia, emotional tension, and a variety of additional alarming 

 stimuli. A variety of chemical agents, such as potassium and serotonin, will 

 release the catechol amines from the medulla (Gaddum and Holzbauer, 

 1957). The sympathico-adrenal system represents a major and immediate 

 reaction system of the body to prepare for, or to counteract the effects of, 

 an emergency situation. The acute response is relatively short lived and 

 serves to maintain life and counteract shock until the emergency passes or 

 until longer-acting adaptive systems, such as the pituitary-adrenocortical 

 system, take over and aid in physiologic adaptation to the situation. 



Recent evidence has shown that norepinephrme is normally found in the 

 walls of the arteries (Schmiterlow, 1948), and that it plays a major, per- 

 haps decisive role in the maintenance of normal vascular tonus and reac- 



