2 - The Nature of Pain of Parturition

Abstract

In summary, then, the responses to acute noxious tissue damaging stimulation provoked by injury or disease or abnormal organ function are the net effect of the highly complex interactions of various neural systems and psychological factors. Through the interaction of the afferent systems and neocortical processes, the individual is provided perceptual information regarding the location, magnitude, and spatial and temporal properties of the noxious stimulus which activates motivational tendencies toward escape or attack and permits analysis of multimodal information, past experience, and probability of outcome of different response strategies. The highly complex interactions of the sensory, motivational, and cognitive processes activate the motor systems and also initiate psychodynamic mechanisms that produce the complex physiological, behavioural, and affective responses which usually characterise acute pain. In general, the immediate responses consist of: (1) involuntary (automatic) responses involving segmental and suprasegmental reflex mechanisms normally intended to preserve homeostasis; these are manifested by contraction or spasm of skeletal muscles, glandular, vasomotor, and sudomotor hyperactivity; cardiovascular and ventilatory changes, alteration of other visceral functions, and widespread endocrine responses; and (2) cerebral cortical responses that include: (a) the emotional experience which we call pain; (b) affective reactions of anxiety and apprehension; and (c) operant responses characteristic of overt pain behaviour such as verbalisation (screaming, moaning), grimacing, posturing (splinting), or prompt withdrawal of the injured part, or a combination of these.