Anatomical and Physiological Mechanisms of Arousal, with Special Reference to the Effects of Exercise

A review is presented of literature regarding the physiological mechanisms which might relate to the arousal effects of exercise demonstrated by Davey's paper in this symposium. It is assumed that exercise is associated with raised activity in one of the diffusely-projecting neural systems, the ‘ Reticular Formation ’. It is suggested that the greater activity in this system could arise, on the one hand, as a part of the central programme initiating the muscular activation and associated cardiovascular excitation; and on the other, as a result of afferent feed-back from these peripheral changes. The suggestion is made that the effect of the activation projected from such systems on the sets of cells involved in sequences of neural activity patterns which subserve ‘ mental functions ’ would depend upon the intensity of the activation. If it is low, the level of excitation in the relevant target cells may be insufficient to ensure the correct sequential flow of the patterns. If it is high, the level of excitation may be such as to cause spurious firing in target cells in the patterns concerned and in cells concerned with irrelevant patterns, in either case disturbing the relevant patterns by ‘ noise. ’