стоимость билетов на выставку автомобилей в крокуса
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стоимость билетов на выставку автомобилей в крокуса, Sleep - Wikipedia, Sleep: What It Is, Why It’s Important, Stages, REM & NREM, Why Do We Need Sleep? - Sleep Foundation, Sleep tips: 6 steps to better sleep - Mayo Clinic, Sleep: How Much You Need and Its 4 Stages, About Sleep | Sleep | CDC - Centers for Disease Control and , What happens during sleep — and how to improve it.
The hypothalamus, a peanut-sized structure deep inside the brain, contains groups of nerve cells that act as control centers affecting sleep and wakefulness. 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 sleep/wake cycle (circadian rhythms) with the light-dark cycle. Most blind people maintain some ability to sense light to help them regulate their sleep/wake cycle.The brainstem, which is made up of structures called the pons, medulla, and midbrain, controls the transitions between wake and sleep. Sleep-promoting cells within the hypothalamus and the brain stem produce a brain chemical called GABA, reduces activity in the hypothalamus and the brainstem. The brainstem (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.The thalamus sends and receives information from the senses to the cerebral cortex. The cerebral cortex is the covering of the brain that has many functions, including interpreting and processing short- and 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. 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. 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.The basal forebrain, near the front and bottom of the brain, also promotes sleep and wakefulness, while part of the midbrain acts as a system to help us stay alert during the day. Release of a chemical called adenosine from cells helps make you feel sleepy. 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. Sleep Stages and MechanismsSleep StagesThere are two basic types of sleep: rapid eye movement (REM) sleep and non-REM sleep. Within non-REM sleep, scientists have identified three different stages. Each is linked to specific brain waves and neuronal activity. You cycle through non-REM and REM sleep several times during a typical night, with increasingly longer, deeper REM periods occurring later in the sleep session. , Sleep is a state of reduced mental and physical activity in which consciousness is altered and certain sensory activity is inhibited. During sleep, there is a marked decrease in muscle activity and interactions with the surrounding environment., Sleep is a body process that allows your body to rest, repair and restore itself. You need sleep to function properly. Lack of sleep has links to many health issues..
Everyone needs sleep, but about one in three American adults don’t get enough of it. The consequences of sleep deprivation are serious, so it’s worth learning why sleep matters, how it works, and how to give yourself the best chances of getting a good night’s sleep., Consider simple tips for better sleep, from setting a sleep schedule to including physical activity in your daily routine. Many factors can interfere with a good night's sleep — from work stress and family responsibilities to illnesses. It's no wonder that quality sleep is sometimes elusive., When you sleep, your body rests, recovers and rebuilds itself through four stages. Here’s how much sleep you need to feel rested., Getting enough sleep and good sleep quality are essential for healthy sleep. The amount of sleep you need changes as you age. Talk to your healthcare provider if you have problems sleeping., Rapid eye movement (REM) sleep is another part of your body's normal sleep cycle, lasting from just a few minutes to up to half an hour. REM sleep is also known as dreaming sleep, during which your body is paralyzed but your eyes dart back and forth behind closed eyelids. Your blood pressure increases, and your heart rate and breathing speed up., Sleep is a complex and dynamic process that affects how you function in ways scientists are now beginning to understand. This webpage describes how your need for sleep is regulated and what happens in the brain during sleep..