Conditioned reflex preparation of the organism for muscular work
Activitas Nervosa Superior 4: 284-293
ISSN/ISBN: 0001-7604 PMID: 14013300 Accession: 024380088
In experiments on 60 dogs and 54 human subjects we studied the conditional and unconditional changes that occur in respiration, thermoregulation, blood composition and circulation during locomotor movements on a treadmill. The experimental method was designed to make possible a continuous recording in unanesthetised animals not only during rest, but also during rapid locomotion. The following results were obtained: Unconditional changes: At the beginning of locomotion an increase in cardiorespiratory dynamics is observed. The deepening of respiration and acceleration of heart rate sets in immediately and is probably due to the intervention of conditioned and proprioceptive-visceral reflexes. In the first 10-12 seconds of locomotion the arterial pressure shows an initial drop as a result of vasodilatation and a subsequent rise above the resting levels. The magnitude of these changes is approximately proportional to the degree of muscular strain. Body temperature during normal running is raised by an average of 1oC. Polypnoic respiration and polypnoic salivation immediately set in. The latter occurs mainly during intermissions of the polypnoic respiration and exhibits a definitely intermittent character. During locomotion blood composition undergoes marked changes. Lactic acid concentration, specific gravity, packed cell volume, and red and white cell counts rise. Conditional changes: During sham running of the dogs, mediated through conditioned reflexes, changes also take place in all measured values. These changes are quantitatively the same as the unconditional changes, but their magnitude is only 50-75 per cent of that of unconditioned changes. In human subjects conditioned reflex changes in respiratory dynamics are quickly elaborated to signals of muscular work. In contradistinction to our observations on dogs, conditional response reflexes in human subjects are rapidly extinguished when unreinforced.