COORDINATION AND CONTROL: (2) THE ENDOCRINE GLANDS 131 



condition, but it enables the body to live with it and perhaps in the end to over- 

 come it through other body defenses. In addition to this major function cortisone 

 performs many lesser ones. It is involved in maintaining the supply of carbo- 

 hydrate fuel to the muscles, in the balancing of important components of the 

 blood, in control of the rate of glucose combustion in the muscles, in making the 

 circulatory system leakproof , and in keeping down the concentration of potassium 

 and nitrogenous wastes in the blood. Perhaps its major regulatory role is merely 

 the sum of all these and other minor ones. As already noted, cortisone has a 

 reciprocal relation to ACTH; it inhibits production of that hormone, while ACTH 

 stimulates formation of cortisone. The two work as a balanced system. 



Adrenalin (also called adrenine or epinephrin) is the hormone produced by the 

 adrenal medulla. In contrast to cortisone, its chemical structure and mode of 

 action are well known. It was the first hormone to be isolated in pure form and 

 chemically identified. 



Amberson and Smith describe the action of adrenalin as follows. "When we 

 inject an extract of the adrenal medulla into the arm of a human being, its effects 

 are felt almost immediately. The skin and face become pale, the heart beats more 

 strongly but slowly, and blood pressure rises, sometimes doubling itself in a few 

 seconds. The subject experiences a feeling of anxiety or apprehension sometimes 

 accompanied by marked muscular tremors, an empty feeling in the pit of the ' 

 stomach, and shortness of breath. All activity ceases in the stomach and intestines. 



"These more obvious effects of adrenalin result chiefly from its actions upon 

 smooth muscle. The effect of the hormone upon the stomach and intestine is to 

 inhibit their action, a change of which we become vaguely aware in consciousness. 

 The slowing of the heart and shortness of breath are the result of carotid sinus 

 reflexes inaugurated by the high blood pressure. If the cardiac nerves are cut in 

 an experimental animal the effect of adrenalin injections is to speed the heart as 

 well as to strengthen its beat, by direct chemical action. But when the nerves are 

 intact a reflex inhibition overcomes the direct chemical effect, in the interest of 

 preventing too high a rise in blood pressure. Adrenalin also causes a transforma- 

 tion of muscle and liver glycogen into glucose which appears in the blood stream. 

 The hormone is a very efficient agent for increasing the level of the blood sugar 

 in time of crisis. It also shortens the coagulation time of the blood." 



Here is a description of a body all ready to fight or run; the function of adrenalin 

 is obviously the preparation of the body to meet an emergency. Transportation 

 by the circulatory system is speeded up, and the blood is shunted from the viscera 

 to the skeletal muscles. Fuel (glucose) for muscle use is poured into the blood, and 

 more oxygen is made available so that this fuel can be rapidly used by the mus- 

 cles. The body is thus prepared for a maximal physical effort. Even the clotting 

 time of the blood is shortened, as if in anticipation of possible injury. The sensa- 

 tion of pain, or the emotions of anxiety, fear, or anger bring this hormone mecha- 

 nism into play. The adrenal medulla is controlled by the sympathetic division of 

 the autonomic nervous system. Impulses set off by the above-mentioned responses 

 to environmental stimuli travel from the brain to the adrenals and cause imme- 

 diate liberation of adrenalin into the blood stream. 



Pancreas. Although the pancreas produces an external digestive secretion, it 

 functions also as an endocrine gland. Certain of its tissues, known as the islands 



