Answer
This situation could represent one in which blood pressure decreases in the head because one rises quickly from a prone position to a standing posture. The baroreceptos would inform the cardiovascular system of the pressure change. In response the sympathetic and parasympathetic feedback from the CV center would would return the vascular parameters-- BP, HR, CO-- to hemostasis.
Work Step by Step
If one rises suddenly from a prone position,gravity would pull blood away from the head and neck, and cause it to pool in the free limbs. As a consequence blood pressure would fall in the head and neck. This pressure change would be sensed by the baroreceptors of the cardiac sinus, and aortic arch . The baroreceptors would slow the rate at which impulses were sent to the cardiovascular center. The CV center would respond by increasing sympathetic stimulation of the myocardium and the adrenal medulla; concurrently, it would also decrease cardiac parasympathetic stimulation. This combined feedback would serve to increase heart rate and peripheral resistance. Hemostasis would be reestablished as blood pressure and cardiac output returned to normal. This cardiovascular center reflex usually occurs very quickly in an healthy adult. However, if it is delayed, as sometimes happens in elderly persons , fainting may ensue.
