If the person does not fall into a fully flat, supine position, and the head remains elevated above the trunk, a state similar to a seizure may result from the bloods inability to return quickly to the brain, and the neurons in the body will fire off and generally cause muscles to twitch very slightly but mostly remain very tense.The autonomic nervous systems physiological state (see below) leading to loss of consciousness may persist for several minutes, so

If patients try to sit or stand when they wake up, they may pass out again
The person may be nauseated, pale, and sweaty for several minutes or hours

Causes
Reflex syncope occurs in response to a trigger due to dysfunction of the heart rate and blood pressure regulating mechanism. When heart rate slows or blood pressure drops, the resulting lack of blood to the brain causes fainting. Vasovagal
Typical triggers include:

Prolonged standing
Emotional stress
Pain
The sight of blood
Fear of needles
Time varying magnetic field (i.e. transcranial magnetic stimulation)

Situational
After or during urination (micturition syncope)
Straining, such as to have a bowel movement
Coughing
Swallowing
Lifting a heavy weight

Carotid sinus
Pressing upon a certain spot in the neck. This may happen when wearing a tight collar, shaving, or turning the head. Pathophysiology
Regardless of the trigger, the mechanism of syncope is similar in the various vasovagal syncope syndromes.
Reflex syncope is a brief loss of consciousness due to a neurologically induced drop in blood pressure and/or a  decrease  in  heart  rate. Before an affected person passes out, there may be sweating, a decreased ability to see, or ringing in the ears. Occasionally, the person may twitch while unconscious. Complications of reflex syncope include injury due to a fall.Reflex syncope is divided into three types: vasovagal, situational, and carotid sinus. Vasovagal syncope is typically triggered by seeing blood, pain, emotional stress, or prolonged standing. Situational syncope is often triggered by urination, swallowing, or coughing. Carotid sinus syncope is due to pressure on the carotid sinus in the neck. The underlying mechanism involves the nervous system slowing the heart rate and dilating blood vessels, resulting in low blood pressure and thus not enough blood flow to the brain. Diagnosis is based on the symptoms after ruling out other possible causes.Recovery from a reflex syncope episode happens without specific treatment. Prevention of episodes involves avoiding a persons triggers. Drinking sufficient fluids, salt, and exercise may also be useful. If this is insufficient for treating vasovagal syncope, medications such as midodrine or fludrocortisone may be tried. Occasionally, a cardiac pacemaker may be used as treatment. Reflex syncope affects at least 1 in 1,000 people per year. It is the most common type of syncope, making up more than 50% of all cases.