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As described in the section Anatomy of Sleep, people who act…

As described in the section Anatomy of Sleep, people who act out dreams physically during sleep (such as sleep walkers) may have problems in the signal system in which part of the brain? Anatomy of Sleep 5. Several structures within the brain are involved with sleep. The hypothalamus, a peanut-sized structure deep inside the brain, contains groups of nerve cells that act as control centers affecting sleep and arousal.  Within the hypothalamus is the suprachiasmatic nucleus (SCN) – clusters of thousands of cells that receive information about light exposure directly from the eyes and control your behavioral rhythm.  Some people with damage to the SCN sleep erratically throughout the day because they are not able to match their circadian rhythms with the light-dark cycle.  Most blind people maintain some ability to sense light and are able to modify their sleep/wake cycle. 6. The brain stem, at the base of the brain, communicates with the hypothalamus to control the transitions between wake and sleep.  (The brain stem includes structures called the pons, medulla, and midbrain.)  Sleep-promoting cells within the hypothalamus and the brain stem produce a brain chemical called GABA, which acts to reduce the activity of arousal centers in the hypothalamus and the brain stem.  The brain stem (especially the pons and medulla) also plays a special role in REM sleep; it sends signals to relax muscles essential for body posture and limb movements, so that we don’t act out our dreams. 7. The thalamus acts as a relay for information from the senses to the cerebral cortex (the covering of the brain that interprets and processes information from short- to long-term memory).  During most stages of sleep, the thalamus becomes quiet, letting you tune out the external world.  But during REM sleep, the thalamus is active, sending the cortex images, sounds, and other sensations that fill our dreams.  8. The pineal gland, located within the brain’s two hemispheres, receives signals from the SCN and increases production of the hormone melatonin, which helps put you to sleep once the lights go down.  People who have lost their sight and cannot coordinate their natural wake-sleep cycle using natural light can stabilize their sleep patterns by taking small amounts of melatonin at the same time each day.  Scientists believe that peaks and valleys of melatonin over time are important for matching the body’s circadian rhythm to the external cycle of light and darkness. 9. The basal forebrain, near the front and bottom of the brain, also promotes sleep and wakefulness, while part of the midbrain acts as an arousal system.  Release of adenosine (a chemical by-product of cellular energy consumption) from cells in the basal forebrain and probably other regions supports your sleep drive.  Caffeine counteracts sleepiness by blocking the actions of adenosine. The amygdala, an almond-shaped structure involved in processing emotions, becomes increasingly active during REM sleep. 

As described in the section Anatomy of Sleep, people who act…

As described in the section Anatomy of Sleep, people who act out dreams physically during sleep (such as sleep walkers) may have problems in the signal system in which part of the brain? Anatomy of Sleep 5. Several structures within the brain are involved with sleep. The hypothalamus, a peanut-sized structure deep inside the brain, contains groups of nerve cells that act as control centers affecting sleep and arousal.  Within the hypothalamus is the suprachiasmatic nucleus (SCN) – clusters of thousands of cells that receive information about light exposure directly from the eyes and control your behavioral rhythm.  Some people with damage to the SCN sleep erratically throughout the day because they are not able to match their circadian rhythms with the light-dark cycle.  Most blind people maintain some ability to sense light and are able to modify their sleep/wake cycle. 6. The brain stem, at the base of the brain, communicates with the hypothalamus to control the transitions between wake and sleep.  (The brain stem includes structures called the pons, medulla, and midbrain.)  Sleep-promoting cells within the hypothalamus and the brain stem produce a brain chemical called GABA, which acts to reduce the activity of arousal centers in the hypothalamus and the brain stem.  The brain stem (especially the pons and medulla) also plays a special role in REM sleep; it sends signals to relax muscles essential for body posture and limb movements, so that we don’t act out our dreams. 7. The thalamus acts as a relay for information from the senses to the cerebral cortex (the covering of the brain that interprets and processes information from short- to long-term memory).  During most stages of sleep, the thalamus becomes quiet, letting you tune out the external world.  But during REM sleep, the thalamus is active, sending the cortex images, sounds, and other sensations that fill our dreams.  8. The pineal gland, located within the brain’s two hemispheres, receives signals from the SCN and increases production of the hormone melatonin, which helps put you to sleep once the lights go down.  People who have lost their sight and cannot coordinate their natural wake-sleep cycle using natural light can stabilize their sleep patterns by taking small amounts of melatonin at the same time each day.  Scientists believe that peaks and valleys of melatonin over time are important for matching the body’s circadian rhythm to the external cycle of light and darkness. 9. The basal forebrain, near the front and bottom of the brain, also promotes sleep and wakefulness, while part of the midbrain acts as an arousal system.  Release of adenosine (a chemical by-product of cellular energy consumption) from cells in the basal forebrain and probably other regions supports your sleep drive.  Caffeine counteracts sleepiness by blocking the actions of adenosine. The amygdala, an almond-shaped structure involved in processing emotions, becomes increasingly active during REM sleep. 

In the following sentence from paragraph 10, what does each…

In the following sentence from paragraph 10, what does each refer to? ” Each is linked to specific brain waves and neuronal activity.” 10. There are two basic types of sleep:  rapid eye movement (REM) sleep and non-REM sleep (which has three different stages).  Each is linked to specific brain waves and neuronal activity.  You cycle through all stages of non-REM and REM sleep several times during a typical night, with increasingly longer, deeper REM periods occurring toward morning.  [BLANK-1]