(http://www.talkaboutsleep.com/sleep-disorders/archives/intro.htm)
- Sleep is a physical and mental resting state in which a person becomes relatively inactive and unaware of the environment.
- sleep is a partial detachment from the world, where most external stimuli are blocked from the senses.
- Normal sleep is characterized by a general decrease in body temperature, blood pressure, breathing rate, and most other bodily functions
(http://www.dailymail.co.uk/health/article-90598/What-happens-body-youre-asleep.html)
- Sleep is the time the body can undergo repair and detoxification
- activity in the cortex - the surface of the brain - drops by about 40 per cent while we are in the first phases of sleep
- five different sleep cycles, each lasting about 90 minutes
- The first four stages of each cycle are regarded as quiet sleep or non-rapid eye move-ment (NREM). The final stage is denoted by rapid eye movement (REM)
- first stage: brain waves are small undulations
- second stage: waves intersperse with electrical signals called sleep spindles - small bursts of activity lasting a couple of seconds which keep us in a state of quiet readiness
- stage three: waves continue to deepen into large slow waves. The larger and slower the brain wave, the deeper the sleep
- stage four: reached when 50 per cent of the waves are slow. not taxed mentally and 40% of the blood flow usually reserved for the brain goes to the muscles.
- stage five (REM): there is a high level of brain activity, helps consolidate memory and emotion, as at this point in sleep blood flow rises sharply in several brain areas linked to processing memories and emotional experiences. In areas involving complex reasoning and language, blood flow declines
- the movement of the eyes denotes the different stages of sleep
- first falling into semi-consciousness, the eyes roll. But as we move into deeper sleep, rapid eye movement (REM) occurs when the eyes twitch and dart about
- REM occurs within about 90 minutes of falling asleep and recurs about every 90 minutes throughout the night. It denotes a time when most dreaming is done
- brain activity is high at this point, the muscles of the body are relaxed to a point of virtual paralysis
- Levels of adrenaline and corticosteroids drop and the body starts to produce human growth hormone (HGH).
- A protein hormone, HGH promotes the growth, maintenance and repair of muscles and bones by facilitating the use of amino acids (the essential building blocks of protein).
- Melatonin: Secreted by the pineal gland deep in the brain, it helps control body rhythms and sleep-wake cycles.
- It is mostly during sleep that the sex hormone testosterone and the fertility hormones, follicle-stimulating hormone and leuteinising hormone, are secreted.
- A cancer killer called TNF - tumour necrosis factor - pumps through our veins when we are asleep
- body temperature, along with levels of wakeful hormones such as adrenaline, start to drop
- By about 5am temp has dropped to about one degree centigrade below the temperature it was in the evening
- Low body temperatures increase your likelihood of sleeping deeply and so give the body chance to rest and rebuild. As body temperature starts to rise, it remains more difficult to stay in a deep sleep
- Though a person can change their sleeping position about 35 times a night, the muscles of the body remain relaxed. This gives the chance for tissues to be repaired and restored.
- However, studies indicate that muscles might receive just as much relaxation and repair during simple rest periods and that a state of unconsciousness is not needed for this to take place.
Do animals sleep?
(http://www.sleepfoundation.org/article/how-sleep-works/animals-sleep-there-human-connection)
- "[Mammals] all have the same fundamental sleep cycle," says Adrian Morrison, DVM, PhD, professor of Behavior Neuroscience at the University of Pennsylvania Veterinary Center. "During REM sleep, you see the same kind of eye movement, paralysis and twitching across species."
- Scientists still don't know—and probably never will—if animals dream during REM sleep, as humans do. "How can you prove that another person has dreams? You ask them," says Siegel.
- Sleep schedules also greatly vary from animal to animal. Siegel proposes that these differences are based on the brain metabolism rate of the animal. Smaller animals, who often have higher rates of brain metabolism, tend to require more sleep, while larger animals generally get less sleep
- Unihemispheral sleep in birds and dolphins—where one side of the brain remains awake in sleep—may provide new clues into the human brain
- sleep is evidently necessary for survival. For instance, rats completely deprived of sleep die in a few weeks
(http://www.dailymail.co.uk/health/article-90598/What-happens-body-youre-asleep.html)
HORMONES
- waking hours: the body burns oxygen and food to provide energy. This is known as a catabolic state, (more energy is spent than conserved), using up the body's resources.
- waking state is dominated by the work of stimulating hormones (adrenaline and natural cortisteroids). However, when we sleep we move into an anabolic state (energy conservation, repair and growth take over)
- Every tissue in the body is renewed faster during sleep than at any time when awake.
- Levels of melatonin rise as the body temperature falls, to encourage feelings of sleepiness. The opposite occurs to wake us up.
- immune system's increased production of certain proteins during sleep, as the levels of certain agents which fight disease rise during sleep and drop when we are awake.
BRAIN
- the human brain never decreases inactivity. Studies have shown that the brain is as active during sleep as it is when awake
- Nerve-signaling chemicals called neurotransmitters control whether we are asleep or awake by acting on different groups of nerve cells, or neurons, in the brain.
- Neurons in the brainstem, which connects the brain with the spinal cord, produce neurotransmitters such as serotonin and norepinephrine that keep some parts of the brain active while we are awake.
- Other neurons at the base of the brain begin signaling when we fall asleep
- During stage 1, which is light sleep, Our eyes move very slowly and muscle activity slows.
- People awakened from stage 1 sleep often remember fragmented visual images.
- Many also experience sudden muscle contractions called hypnic myoclonia, often preceded by a sensation of starting to fall. These sudden movements are similar to the "jump" we make when startled
- stage 2 sleep, our eye movements stop and our brain waves (fluctuations of electrical activity that can be measured by electrodes) become slower, with occasional bursts of rapid waves called sleep spindles.
- In stage 3, extremely slow brain waves called delta waves begin to appear, interspersed with smaller, faster waves.
- By stage 4, the brain produces delta waves almost exclusively. It is very difficult to wake someone during stages 3 and 4, which together are called deep sleep. There is no eye movement or muscle activity
MUSCLES
- You have three different types of muscles in your body: smooth muscle, cardiac muscle, and skeletal muscle.
- SMOOTH: also called involuntary muscles — are usually in sheets, or layers, with one layer of muscle behind the other
- can't control smooth muscles
- bladder, behind eyes, uterus, etc
- CARDIAC: muscle that makes up the heart
- heart contract to pump blood out and then relax to let blood back in after it has circulated through the body
- like smooth muscle, cardiac muscle works all by itself with no help from you
- SKELETAL: sometimes called striated muscle
- voluntary muscles
- the skeletal muscles work with your bones to give your body power and strength. In most cases, a skeletal muscle is attached to one end of a bone. It stretches all the way across a joint (the place where two bones meet) and then attaches again to another bone
- muscles help keep you upright and standing tall. They also give your body the power it needs to lift and push things
- take in tons of information about the world around you — shapes, colors, movements, and more. Then they send the information to your brain for processing so the brain knows what's going on outside of your body
- blinking: both a voluntary and involuntary action, (you can blink whenever you want to, but also happens without you even thinking about it)
- step into bright light, the eyelids squeeze together tightly to protect your eyes until they can adjust to the light
- eyelids shut automatically to protect the eye from possible danger
- lacrimal glands, which make tears. Every time you blink your eye, a tiny bit of tear fluid comes out of your upper eyelid.
- tears wash away germs, dust, or other particles that don't belong in your eye
- Animals use their muscular and skeletal systems for support, locomotion, and maintaining their shape
- Rapid muscular contraction is important in generating internal heat, another homeostatic function.
- The brain directs the things we choose to do (like walking and talking) and the things our body does without thinking (like breathing). The brain is also in charge of our senses (sight, hearing, touch, taste, and smell), memory, emotions, and personality.
- Cerebrum- controls reading, thinking, learning, speech, and emotions
- Cerebellum - The cerebellum controls balance and complex actions like walking and talking.
- Brain Stem - It controls hunger and thirst. It also controls breathing, body temperature, blood pressure, and other basic body functions.
(http://www.dailymail.co.uk/health/article-90598/What-happens-body-youre-asleep.html)
- those who sleep less than six hours a night have a shorter life expectancy than those who sleep for longer
- Research suggests that sleeping more when fighting infectious illness aids recovery
- Getting enough sleep can also help resist infection, as some studies of healthy young adults have shown that moderate amounts of sleep deprivation reduce the levels of white blood cells which form part of the body's defence system.
- people who stayed up until 3am had one-third fewer cells containing TNF the next day, and that the effectiveness of those remaining was greatly reduced
- Ensuring regular periods of sleep at night lets the bodyclock regulate hormone production, so that you feel wakeful and alert during the day and ready to enjoy restorative sleep at night.
- Sleep is a necessary and vital biological function.
- It is essential to a person's physical and emotional well being.
- Studies have shown that without enough sleep, a person's ability to perform even simple tasks declines dramatically
- average sleep-deprived individual may experience impaired performance, irritability, lack of concentration, and daytime drowsiness
- less alert, attentive, and unable to concentrate effectively. Additionally, because sleep is linked to restorative processes in the immune system, sleep deprivation in a normal adult causes a biological response similar to the body fighting off an infection.
(http://www.dailymail.co.uk/health/article-90598/What-happens-body-youre-asleep.html)
- We spend about one-third of our lives asleep
- Six to eight hours per day is the average amount of sleep a person needs. That's about one-third of a lifetime!
- As a population, we sleep about 1 to 1.5 hours less than we did 100 years ago.
- experts suggest that the best way to determine personal sleep requirements is by waking up without an alarm clock. The amount of time spent sleeping would be the personal requirement
- the amount of sleep a person needs does not decrease with age
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