The vertebrobasilar arteries are the blood vessels in the back of the neck, next to the spinal cord, that supply the brainstem -- the portion of the brain that, among other things, is responsible for maintaining consciousness. A blockage of blood flow in the vertebrobasilar arteries can cause syncope.
1. NREM-a recurring sleep state during which rapid eye movements do not occur and dreaming does not occur; accounts for about 75% of normal sleep time. nonrapid eye movement, nonrapid eye movement sleep, NREM sleep, orthodox sleep. sleep, slumber-a natural and periodic state of rest during which consciousness of the world is suspended; he didn't get enough sleep last night; calm as a child in dreamless slumber. 1  Facebook.
REM sleep follows NREM sleep and occurs 4-5 times during a normal 8-hour sleep period. The first REM period of the night may be less than 10 minutes in duration, while the last may exceed 60 minutes. The NREM-REM cycles vary in length from 70-100 minutes initially to 90-120 minutes later in the night.