Siegfried experiences a hemorrhage in an artery, and now blood is leaking out of the resulting hole. His blood pressure decreases. Draw a flow chart illustrating the cardiovascular reflex responses that follow to compensate for the drop in blood pressure.

Question

What will be an ideal response?

Answer 1

As blood exits the vasculature, there is a loss in blood volume, which in turn causes the systemic blood pressure to
decrease. Baroreceptors (stretch receptors) in the carotid and artery walls are less stretched, and therefore their
action potential firing frequency decreases. The baroreceptors project to the cardiovascular control center in the
medulla oblongata. In response to decreased baroreceptor input, the cardiovascular control center stimulates
sympathetic output and inhibits parasympathetic output. Sympathetic activity causes vasoconstriction and
consequent increases in peripheral resistance and blood pressure. Decreased parasympathetic activity causes the SA
node firing rate to increase and therefore heart rate increases. Combined with the sympathetic stimulation of the
ventricles and consequent increase in contraction force, cardiac output increases as a result, also helping to increase
blood pressure.