428 



PHYSIOLOGY OF STRESS 



toses, and adiadochokineses on any neurologi- 

 calward. What may happen in these systems 

 under the stress of emotion has been pointed 

 out by Kennard (69). The physiological 

 changes observed in emotion may be no less 

 of importance because of their afferent than 

 because of their efferent or expressive man- 

 ifestations. 



Channels of such feedback effects are nu- 

 merous (26, 52, 84, 91, 93). They include 

 the whole range of psychophysiological ac- 

 tivity, humoral, chemical autonomic, neuro- 

 physiological, and, we shall try to show, 

 psychological. Humoral effects upon the 

 brain involving particularly effects of ad- 

 renahn, pituitrin, insuhn, sjonpathin, and 

 acetylchohne probably take many forms, but 

 only one of these, the most definite and well 

 estabhshed, the effects upon the blood vessels, 

 will be considered. The susceptibihty of the 

 cerebral blood vessels to changes in carbon 

 dioxide has been well estabhshed (24, 25, 48, 

 50, 52, 92). The effects of hyperventilation 

 with blowing off of carbon dioxide are readily 

 demonstrable insusceptible persons by means 

 of the electroencephalogram (27, 29, 76). 

 As httle as three percent carbon dioxide or 

 a cerebral vasodilator such as glyceryl tri- 

 ni trite may prevent the effect (92). 



That the parasympathetic supply to the 

 brain via the facial and greater superfical 

 petrosal nerves may serve as a regulatory 

 feed-back mechanism has been demonstrated 

 (17, 24). Feed-back effects via sympathetic 

 pathways are suggested by the work of 

 Murphy and Gellhom (87, 88). 



That the entire sensory system, including 

 the proprioceptive afferent systems, provides 

 a mechanism controlling bodily responses is 

 commonly recognized (80), but that these 

 afferent processes serve as parts of an ex- 

 tensive integrated coordinating feedback 

 mechanism maintaining tone and governing 

 reaction needs emphasis. That they hke- 

 wise contribute substance to that complex 

 subjective state called "consciousness" will 

 be considered in Section IV. 



D. Stress as a Function of Chronic 

 and Accumulated Impairment 



Long submarine patrols where attendant 

 dangers and discomforts are extended in time, 

 and where the conditions of stress become 

 more or less chronic, introduce another fac- 

 tor: impairment of the capacity of the or- 

 ganism to react to stress. These conditions 

 are hkely to result in true organic or physio- 

 logical impairment of the type that can be 

 demonstrated by microscopic and chemical 

 methods. Cumulation of these effects may 

 eventually lead to a condition such that the 

 boat can not be competently manned in all 

 of its functions. Under such conditions per- 

 sistence of psychophysiological effects after 

 the source of disturbance has been removed 

 may be identified in various forms of "op- 

 erational stress" or "combat fatigue" (16, 

 34, 55, 82). 



1. Sleep 



The capacity of the organism to function 

 adequately despite wide variations in the 

 amount and distribution of its usual sleep J 

 periods has received much cMnical and labo- l 

 ratory study, although there is still some 

 disagreement with respect to the amount of 

 sleep that is necessary and desirable. The 

 watch system of the Navy has always re- 

 quired a flexible and frequently interrupted 

 schedule. Furthermore, in submarine duty 

 the usual hght-dark diurnal cycle may be 

 missing or reversed for weeks on end. There 

 is some evidence that younger individuals 

 adapt more readily to imposed changes in 

 their wake-sleep rhythm (73). 



Even before conditions of extreme sleep- 

 lack are encountered there are performance 

 changes that are of vital interest to a sub- 

 mariner. Rather surprisingly, these changes 

 are not marked for such tests as steadiness, 

 tapping, static ataxia and visual acuity, or 

 for such measures as blood pressure, heart 

 rate, temperature, and basal metabohsm (3). 

 There is increased sensitivity to pain and, 

 more important, loss of memory, hallucina- 



