Now that you have seen how a healthy heart works, let's look at what happens with syncope.
Normally when you stand up, your heart rate and blood pressure increase to push enough blood to your brain, while fighting the pull of gravity.
However, if you have "simple fainting", standing up can result in a sudden drop in heart rate and blood pressure. If your blood pressure falls too low and there is not enough blood going to your brain, this can cause you to faint. Fainting is nature's way of getting you to lie back down so that blood can more easily flow to your brain.
A more serious type of fainting can be caused by heart valve problems. Heart valves are made of thin flaps of tissue that open and close to let blood through. Sometimes valves will stenose, or narrow. When this happens, blood is forced through a smaller opening than normal. So, less blood circulates through the heart and to the brain. Again when not enough blood is flowing to your brain, this may cause you to faint.
Other serious causes of fainting can be related to heart attacks, abnormal heart rhythms or other abnormalities in the heart or brain. But whatever the cause of the syncope or fainting spells, the end result is not enough blood going from your heart to your brain.