How does nervous input in a human cause increase cardiac output during exercise?

The nervous system can be divided into two branches-the parasympathetic branch and the sympathetic branch. The activity of the sympathetic nervous system is increased in response to exercise. This response to exercise is controlled by the medulla. These impulses activate travel to the sinoartrial node which is the pacemaker of the heart. As a result, the contractility of the heart is increased and furthermore, the rate of the heart is also increased. This increases cardiac ouput as cardiac output= heart rate x stroke volume.