What Makes People Faint?
The most urgent need of the body-more important even than food or drink-is oxygen, which is found in the air we breathe. When we breathe in, the oxygen is absorbed through our lungs into the blood which is carried round the body by the veins and arteries with the heart working as a pump.
The most important place for the blood and oxygen to reach is the brain which controls the rest of the body through the nervous system. If the brain does not receive enough blood and oxygen, it can no longer control the limbs, and the person’s legs give way under him in a faint.
There are all sorts of ways this could happen. It might be due to something blocking the blood flow, a tight collar or some more serious cause. But fainting is mostly due to stuffy atmospheres, lacking in oxygen.
If a person with you faints, get the victim into the fresh air, loosen the clothes and put the head between the knees, so that the weak blood supply does not have to climb upwards into the head, but can run downwards. Usually the circulation will get going again quickly and the person will soon come round, with no damage done.
Fainting is most commonly caused by a temporary glitch in the autonomic nervous system. This is sometimes known as neurally mediated syncope. The autonomic nervous system is made up of the brain, nerves and spinal cord. It regulates automatic bodily functions, such as heart rate and blood pressure.
An external trigger can temporarily cause the autonomic nervous system to stop working properly, resulting in a fall in blood pressure and fainting. The trigger may also cause your heartbeat to slow down or pause for a few seconds, resulting in a temporary interruption to the brain’s blood supply. This is called vasovagal syncope.
Fainting can also be caused by a fall in blood pressure when you stand up. This is called orthostatic hypotension, and tends to affect older people, particularly those aged over 65. It’s a common cause of falls in older people. When you stand up after sitting or lying down, gravity pulls blood down into your legs, which reduces your blood pressure.
The nervous system usually counteracts this by making your heart beat faster and narrowing your blood vessels. This stabilises your blood pressure. However, in cases of orthostatic hypotension, this doesn’t happen, leading to the brain’s blood supply being interrupted and causing you to faint.