Related Experiment Videos
Control of left ventricular function during acceleration-induced blood volume shifts
G N White1, C F Knapp, J M Evans
1Department of Physiology and Biophysics, University of Kentucky, Lexington 40536-0084.
Aviation, Space, and Environmental Medicine
|May 1, 1988
Summary
Sudden removal of G-force causes blood to return to the chest, increasing heart volume. This response, crucial for cardiovascular adaptation, primarily relies on the Frank-Starling mechanism, not the autonomic nervous system.
Area of Science:
- Cardiovascular Physiology
- G-force effects on circulation
- Autonomic nervous system regulation
Background:
- G-force exposure causes peripheral blood pooling.
- Sudden G-force removal mobilizes blood centrally.
- Understanding cardiac response to altered blood volume is critical.
Purpose of the Study:
- To investigate left ventricular volume changes after G-force cessation.
- To determine the role of the autonomic nervous system in this response.
- To elucidate the primary mechanism of cardiac adaptation to altered loading conditions.
Main Methods:
- Dogs were subjected to +2 Gz force, followed by rapid release.
- Left ventricular volume was measured using ultrasound.
- Experiments were repeated after autonomic blockade (propranolol, atropine, phenoxybenzamine).
Main Results:
- Left ventricular volume significantly increased after G-force release (p < 0.05).
- Cardiac function changes were similar before and after autonomic blockade.
- No significant difference in ventricular volume response was observed after blockade.
Conclusions:
- The autonomic nervous system plays a minimal role in regulating left ventricular volume post-G-force.
- The Frank-Starling mechanism is the primary driver of cardiac adaptation to altered load.
- Cardiac output regulation is largely independent of autonomic control during this specific scenario.