together, these two systems control many important things, like how fast the heart beats and how hard it squeezes. in the cardiac center, there are special nerves that will make the heart beat harder and faster, called "excitatory nerves". there are also "inhibitory nerves", which will make the heart beat slower and not as hard. if a person's blood pressure gets too low, the cardiac center will send a message to the excitatory nerves, telling them to make the heart beat faster and harder. this raises the blood pressure. if the blood pressure gets too high, the cardiac center sends a message to the inhibitory nerves, which slow the heart down and make it not beat so hard. this lowers the blood pressure. in a healthy person, the cardiac center balances out the signals it sends to these sets of nerves, to keep the blood pressure normal.