Causes of fainting

Symptoms of fainting 

Treatment fainting 

Fainting (syncope) is a defence mechanism used by the brain. If the supply of blood and oxygen to the brain becomes too low, the brain will immediately take any available blood and oxygen from the rest of the body at the expense of other bodily functions.
Your breathing rate will be increased (hyperventilation) as your brain tries to increase its supply of oxygen. Your heart rate will also increase, to pump more blood from the rest of your body to your brain.
The increase in heart rate will lead to a loss of blood pressure in the rest of your body (hypotension) as blood is diverted to your brain. The combination of hyperventilation and hypotension can then lead to a temporary loss of consciousness and muscle weakness, resulting in fainting.
There are different types of fainting which are caused by the blood supply to the brain being interrupted for different reasons. The different types of fainting are explained below.






Neurally mediated syncope


Neurally mediated syncope is also called reflex syncope. Neurally means that it is related to the nervous system, which is made up of your brain, nerves and spinal cord. There are three types of neurally mediated syncope. They are:

• vasovagal syncope
• situational syncope
• carotid sinus syndrome

These are explained in more detail below.

Vasovagal syncope

Vasovagal syncope occurs when something triggers a temporary malfunction in your autonomic nervous system. The autonomic nervous system is the part of the nervous system responsible for regulating many of the body’s automatic functions, such as heartbeat and blood pressure.
The malfunction in the autonomic nervous system causes a drop in your blood pressure and a reduction in your heartbeat. This leads to a temporary interruption to your brain’s blood supply.


Vasovagal syncope may be caused by:

• sudden exposure to an unpleasant sight or experience, such as the sight of blood
• standing for long periods of time
• spending a long time in hot or stuffy environments
• a sudden intense episode of stress, emotional upset, fear or anxiety
• a sudden feeling of pain

Situational syncope

Situational syncope is also a type of fainting related to the nervous system. It occurs when a bodily function or activity places a sudden strain on your autonomic nervous system. Possible causes of situational syncope include:

• coughing
• sneezing
• swallowing
• laughing
• passing stools
• urinating

some physical activities, such as weightlifting, although this could also be a sign of an underlying heart problem (see cardiac syncope, below)

Situational syncope may also occur after eating a meal or exercising.

Carotid sinus syndrome

The carotid sinus is a collection of sensors in the carotid artery. The carotid artery is located in your neck and is the main artery that supplies blood to your brain. The carotid sinus helps to regulate the flow of blood through the carotid artery into your brain.
Some people can develop a hypersensitive carotid sinus. This means that any physical stimulation of the carotid sinus can cause the sensors suddenly to trigger a drop in blood pressure, resulting in fainting. This condition is known as carotid sinus syndrome.
Examples of physical stimulation that may affect your carotid sinus include:

• turning your head to one side
• wearing a tight collar
• shaving over the part of your neck that contains the carotid sinus

Carotid sinus syndrome is very rare in people who are under 40 years of age. It is most common among older men.







Symptoms of fainting 
Treatment fainting 

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