Some are psychological, i.e. the fear response causes them to faint, or physical, such as the fainting that occurs when we over exert ourselves. Vagal nerve fainting (also known as vasovagal syncope) is quite simply any loss of consciousness caused by the vagus nerve. The vagus nerve runs directly from the brain stem, in front of the ears and down the neck towards the chest and abdomen. It branches off in several places to provide communication with the brain to a number of organs, such as the heart and the stomach.
The floor of the third ventricle is formed by a number of structures including the hypothalamus, subthalamus, mammilary bodies, infundibulum (pituitary stalk), and the tectum of the midbrain. The lateral walls of the third ventricle are formed by the walls of the left and right thalamus.
Inside the brain, there are four cavities, called ventricles. The right and left lateral ventricles and the third and fourth ventricles compose the ventricular system. The fourth ventricle contains cerebrospinal fluid. It has a diamond shape and is located in the upper portion of the medulla.