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Cardiovascular regulation in canines during low-frequency acceleration
The American Journal of Physiology
|December 1, 1982
Summary
Cardiovascular regulation effectively minimizes arterial pressure disturbances from acceleration at low frequencies. Neural mechanisms are crucial below 0.052 Hz, with circulatory system characteristics dominating at higher frequencies.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Regulation
- Biomedical Engineering
Background:
- Cardiovascular regulation is vital for maintaining arterial pressure during dynamic physiological challenges.
- Understanding the interplay of neural and intrinsic circulatory mechanisms is key to assessing tolerance to acceleration stress.
Purpose of the Study:
- To investigate integrated cardiovascular regulation during sinusoidal acceleration in dogs.
- To differentiate the roles of neurally mediated versus intrinsic circulatory responses to acceleration.
Main Methods:
- Utilized chronically-instrumented, unanesthetized dogs subjected to sinusoidal whole-body spinal-axis acceleration (+/- 2 Gz) below 0.25 Hz.
- Compared cardiovascular responses in normal (reflexive) and pharmacologically blockaded (nonreflexive) states.
Main Results:
- Neural mechanisms were most effective below 0.012 Hz, with effectiveness decreasing between 0.012 and 0.052 Hz.
- Above 0.052 Hz, circulatory system biomechanics, not neural control, primarily managed arterial pressure.
- Systemic vascular responses were largest for frequency; heart rate and stroke volume oscillations decreased with increasing frequency.
Conclusions:
- Integrated neural control is essential for cardiovascular stability at low acceleration frequencies.
- At higher frequencies, intrinsic circulatory properties provide essential protection against acceleration-induced pressure disturbances.
- Both cardiac and vascular neural control mechanisms contribute to cardiovascular regulation, with their relative importance varying with acceleration frequency.