How fast does blood go to your heart?

Answer 1

you are asking about "cardiac output," which is the amount of blood that gets pumped out of the heart, usually given in liters per minute (remember that since the circulatory system is a closed loop, volume of blood pumped out must equal blood coming back to the heart, assuming you are not actively bleeding). Cardiac output in a normal adult is 5-6 L/min at rest, but can increase to 25 L/min or more during strenuous exercise. Cardiac output (CO) is equal to the Stroke Volume (SV, or the volume of blood pumped with each heart beat) times the heart rate (number of beats per minute). If you have taken physics, you should be familiar with Ohm's law: V=IR. There is also a correlating equation for the circulatory system, which is Mean Arterial Blood Pressure = Cardiac Output times Systemic Vascular Resistance, or MAP = CO x SVR. You can think of MAP as the voltage, CO as the current, and SVR as resistance. This equations relates your cardiac output to your blood pressure and your vascular resistance (how clamped down or open your blood vessels are). Your body is set up to try to maintain a constant blood pressure by adjusting the vascular resistance or cardiac output (which in turn is dependent on stroke volume and heart rate). One good example is active exercise: the blood vessels going to your muscles open up to allow for increased blood flow, which decreases overall vascular resistance. According to the relation above, decreased SVR with no change in CO will cause your blood pressure to drop - enough of a drop in blood pressure will cause you to pass out. Therefore, your cardiac output MUST increase to maintain a constant blood pressure. During exercise, I'm sure you have noticed that both your heart rate increases, but your heart is also beating more strongly, which pumps more blood with each beat.