NBME 21 Answers ↦
Hyotension will lead to decreased arterial pressure and DECREASED stretch. This leads to decreased afferent barcreceptor firing (carotid sinus and aortic arch). This leads to an increase in efferent sympathetic firing and decreased efferent PNS stimulation. This leads to vasoconstriction, increased HR and increased BP.
The way I remember this, carotid massage slows the heart. So baroreceptor stimulation (more impulses) increases parasympathetic output.
FA 2018 pg 291 has helpful image/description