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Skin sympathetic outflow during head-down neck flexion in humans
C A Ray1, K M Hume, T L Shortt
1Department of Exercise Science, University of Georgia, Athens 30602, USA. caray@coe.uga.edu
The American Journal of Physiology
|October 10, 1997
Summary
Head-down neck flexion (HDNF) increases muscle sympathetic nerve activity but not skin sympathetic nerve activity (SSNA) in humans. Vestibular stimulation may differentially affect sympathetic nervous system outflow.
Area of Science:
- Physiology
- Neuroscience
- Cardiovascular Research
Background:
- Previous studies showed head-down neck flexion (HDNF) increases muscle sympathetic nerve activity.
- The current study investigated whether HDNF also affects skin sympathetic nerve activity (SSNA).
Purpose of the Study:
- To determine if head-down neck flexion (HDNF) activates skin sympathetic nerve activity (SSNA).
- To examine the differential effects of vestibular stimulation on sympathetic outflow.
Main Methods:
- Measurements included SSNA, heart rate, arterial pressure, skin blood flow, and calf blood flow in 12 subjects.
- Calf vascular resistance was calculated. Muscle and skin sympathetic nerve activity were measured simultaneously in three subjects.
Main Results:
- HDNF did not significantly alter heart rate or arterial pressure, though a slight increase in diastolic and mean arterial pressure was observed.
- Calf blood flow decreased by 22%, and calf vascular resistance increased by 46% during HDNF.
- Skin sympathetic nerve activity (SSNA) did not change significantly, while muscle sympathetic nerve activity consistently increased.
Conclusions:
- HDNF activates muscle sympathetic nerve activity but not skin sympathetic nerve activity (SSNA) in humans.
- Vestibular stimulation may lead to differential activation of sympathetic outflow pathways.
Keywords:
Non-programmatic
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