Spontaneous Motor Activity Change in normoxic and hypoxia atmospheres, Effects of CO2.

This explains the differences in spontaneous motor activity that Paula experienced when she was ill. During the first year of her illness, Paula felt strangely awful, full of paralyzing fear and very distressed ; [please see previous blog on the effects of abnormal ratio’s of CO2 on mood]. Her level of spontaneous motor activity was much reduced during this period, especially in her home, where she barely moved at all. Her spontaneous motor behaviour was inhibited, just as Dr Emile described, in his studies of manic depressive insanity in 1926. She could not easily or sometimes at all produce the behaviour she intended. It was the oddest thing. It was confusing to her.

After a year of this inhibition of spontaneous motor behaviour, including inhibition of the motor act of breathing [too slow], speech [physically made difficult due to stiffness of muscles of the face, and thought [links to motor function??] and continual chronic fear and distress, a switch occurred. Spontaneous motor behaviour suddenly was not only released from being inhibited but like a spring that has been depressed [physically] and is suddenly released….energy was released in a speedy and exaggerated manner…to much, too fast, too excited…what one typically sees in mania. Paula is pretty sure that the disinhibition and suddenly release of motor behaviour was accompanied by increased speed of the motor act of breathing [rising breathing rate sustained during mania].

Dr Emile Kraepelin [1926] suggested that behaviour in the depressive stage of manic depressive insanity was inhibited and behaviour in the same person after the switch to mania was excited. Since breathing was inhibited and slow in the depressive stage, and breathing was too fast [and period] in mania, Kraepelin thought that pH of the blood played an important part.

The study below seems to add weight to Kraepelin’s argument.

The effect of carbon dioxide on spontaneous locomotor activity in normoxic and hypoxic atmospheres

Psychonomic Science volume 10, pages17–18(1968)Cite this article


Eleven male Sprague-Dawley rats were run in an activity wheel for three 20 min sessions under each of four atmospheres varying in O2 concentration (21% or 8%) and CO2 concentration (0% or 5%), remainder N2. Results indicated an interaction of CO2and O2 levels. The addition of 5% CO2 to a normoxic atmosphere reduced spontaneous locomotor activity. The addition of 5% CO2 to a hypoxic atmosphere increased the level of activity. These data are consistent with the findings of other investigators concerning the effects of CO2 and O2 on the central nervous system.

These effects he describes would affect any person, presumably. A person with damage to their ventilatory system would be even more at risk of hypercapnia and the ratio of PCO2 and PO2 might explain the stages of decreased and/or increases in [involuntary] spontaneous behaviour.

Studies that showed that baseline breathing rate in healthy adults varies widely, from 3 breaths per minute to 28 at rest suggests that people at the extremes are more sensitive to additional constraints on breathing from illness as well as being more sensitive to heightened CO2 levels in the air.

It may be that people differ in their tolerance of increased CO2 in the blood, depending on their ability to control their own PCO2. Lung problems will interfere with this but so will ventilatory damage and so will circulatory problems [heart failure] and kidney or liver damage, etc..

The earliest signs of difficulty controlling one’s PCO2/O2 ratio will be the pattern of the 4 vital signs; respiratory rate [and depth], heart rate [and heart signs], blood pressure and body temperature. Sudden and long lasting changes to personality, mood, behavior and cognitive skills will suggest blood pH issues that need correction with supportive medical support to help what ever organ or system is failing.


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