Describe three mechanisms of how adrenergic stimulation of nodal cells and/or cardiocytes increases heart rate and contraction strength.

Watch this animation (http://openstaxcollege.org/l/bloodflow1) to see how blood flows to the brain and passes through the circle ofWillis before being distributed through the cerebrum. The circle of Willis is a specialized arrangement of arteries that ensure constant perfusion of the cerebrum even in the event of a blockage of one of the arteries in the circle. The animation shows the normal direction of flow through the circle of Willis to the middle cerebral artery. Where would the blood come from if there were a blockage just posterior to the middle cerebral artery on the left?

High blood pressure would be a result of ___________ . a high cardiac output and high peripheral resistance a high cardiac output and low peripheral resistance a low cardiac output and high peripheral resistance a low cardiac output and low peripheral resistance