From the Guidelines
Baroreceptor firing decreases in hypotension (low blood pressure).
Rationale
- The baroreflex function is defined by both vagal and sympathetic responses to changes in blood pressure 1.
- A reduction in blood pressure induces an increase in sympathetic outflow to counteract hypotension, which implies a decrease in baroreceptor firing 1.
- During the Valsalva manoeuvre, the hypotension phase (phase II) is characterized by a decrease in blood pressure, which triggers a compensatory increase in heart rate and systemic vascular resistance driven by the sympathetic outflow, indicating a decrease in baroreceptor firing 1.
- The decrease in baroreceptor firing is a physiological response to low blood pressure, aiming to increase cardiac output and blood pressure through sympathetic stimulation and vagal withdrawal 1.
From the Research
Baroreceptor Firing in Hypotension
- In hypotension, baroreceptor firing decreases due to the reduced stretch in the arterial wall 2, 3.
- The decrease in baroreceptor firing leads to an increase in sympathetic nerve activity, which aims to increase blood pressure 4, 5.
- The baroreceptors reset to the new lower blood pressure level, allowing them to maintain their sensitivity to changes in blood pressure 3.
- The resetting of baroreceptors in chronic hypotension is stable and is not accompanied by changes in gain sensitivity, as observed in hypertension 3.
- During hypoxic hypotension, baroreceptor sensitivity decreases, leading to a reduction in the reflex capabilities to sustain simultaneous reductions in oxygen and pressure 5.