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Published on: February 14, 2021
The arterial baroreflex resets with orthostasis
Christopher E Schwartz1, Julian M Stewart
1Department of Physiology, The Center for Hypotension, New York Medical College Valhalla, NY, USA ; Department of Pediatrics, The Center for Hypotension, New York Medical College Valhalla, NY, USA.
Frontiers in Physiology
|December 13, 2012
Summary
The arterial baroreflex helps regulate blood pressure. During orthostasis (standing up), cardiovagal and ventilatory baroreflexes reset, while the sympathetic baroreflex strengthens to defend blood pressure.
Area of Science:
- Cardiovascular physiology
- Autonomic nervous system regulation
- Baroreceptor reflex function
Background:
- Arterial baroreflexes are crucial for short-term blood pressure control.
- Previously, baroreflexes were thought to be inactive during exercise.
- Recent findings show baroreflexes reset during exercise to defend blood pressure.
Purpose of the Study:
- To investigate baroreflex resetting during orthostasis (upright tilt).
- To compare baroreflex responses during orthostasis with those during exercise.
- To analyze the cardiovagal, ventilatory, and sympathetic baroreflexes.
Main Methods:
- Utilized the modified Oxford method to manipulate blood pressure.
- Administered sodium nitroprusside and phenylephrine to alter blood pressure.
- Measured heart rate, ventilation, sympathetic nerve activity, and blood pressure in supine and tilted positions.
Main Results:
- Cardiovagal and ventilatory baroreflexes exhibited resetting without changes in gain or range.
- Sympathetic baroreflex was augmented (increased gain) and shifted.
- Increased peripheral resistance was observed due to sympathetic baroreflex augmentation, enhancing hypotension defense.
Conclusions:
- Arterial baroreflexes, including cardiovagal and ventilatory components, reset during orthostasis.
- The sympathetic baroreflex is augmented during orthostasis, unlike during exercise.
- Functional sympatholysis may explain the difference in sympathetic response between exercise and orthostasis.
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