The pedestrian feels his heart pounding heavily when he has stepped on the curb after having been narrowly missed by a speeding taxi. The student feels an urgency to urinate before a crucial examination. Or a speaker finds his appetite strangely absent at the dinner after which he must make an important and crucial address.
Originally in the time of primitive man, these responses had a clear purpose in protecting the person from wild animals and other concrete perils. In modern society man has few direct threats; the anxiety mainly concerns such psychological states as social adequacy, alienation, competitive success, and so on. But the mechanisms for coping with threats remain the same.
These and many other physical expressions of anxiety/fear can be conveniently linked in the framework of Cannon's "flight/fight" mechanism. The heartbeat is accelerated in order to pump more blood to the muscles which will be needed in the impending struggle. The peripheral blood vessels, near the surface of the body, are contracted and the blood pressure thereby raised to maintain arterial pressure for the emergency needs. This peripheral contraction is the physiological aspect of the popular expression "blanching with fear" [in American English: "turning white with fear"].
The "cold sweat" occurs preparatory to the warm sweat of actual muscular activity. The body may shiver and the hairs of the body stand on end to conserve heat and protect the organism from the increased threat of cold caused by the contraction of peripheral blood vessels. Breathing is deeper or more rapid in order to ensure a plentiful supply of oxygen; This is the "pant of strong excitement." The pupils of the eyes dilate, permitting a better view of threatening dangers; hence the expression "eyes wide with fear." The liver releases sugar to provide energy for the struggle. A substance is released into the blood to effect its more rapid clotting, thus protecting the organism from the loss of blood through wounds.
As a part of placing the organism on this emergency footing, digestive activity is suspended, since all available blood is needed for the skeletal muscles. The mouth feels dry, because of a decreasing of the flow of saliva corresponding to the suspending of the flow of gastric juices in the stomach. The smooth muscles of internal genital organs are contracted. There is a tendency toward voiding of bladder and bowels - again recognized in vernacular expression - which has the obvious utilitarian function of freeing the organism for strenuous activity.
- Rollo May