Why do we yawn?

No one knows why we yawn. There are lots of theories, some talk about it signalling tiredness or getting oxygen to the brain, others mention clearing out stale air from the lungs and reducing blood carbon dioxide levels. It’s widely assumed that yawning occurs because we are tired or bored or because we see someone else doing it, but there isn’t any hard evidence to support these beliefs. Scientists do not purport to know all of the biological mechanisms of the yawn, but tend to agree that a yawn is an involuntary respiratory reflex, which regulates the carbon dioxide and oxygen levels in the blood.Technically, a yawn is the reflex opening of the mouth followed by the deep inhalation and slow exhalation of oxygen. you inhale oxygen and your body uses it up. The body makes a waste product called as carbon dioxide that is exhaled from the lungs when you breathe out. Scientists speculate that the onset of a yawn is triggered either by fatigue, or by sheer boredom as, at those times, breathing is shallow, and little oxygen is carried to the lungs by the oxygen-toting cardiovascular system. When you are sleepy, bored or tired, you breathe more slowly. Your body requires oxygen and needs to throw out the carbon dioxide. So, your brain makes you take an extra breath, which is deep and long called a yawn, so that you can take in more of oxygen and give out carbon dioxide fully. We know it's involuntary because we do it even before we are born. Research shows that 11-week-old fetuses yawn. when it is a well-known fact that they do not intake oxygen into their lungs until after live birth. Senju and colleagues from the University of Tokyo showed videos of people yawning or making mouth movements to 24 children with autism spectrum disorder and to 25 non-ASD children. Both groups of children yawned the same number of times while watching the video of general mouth movements, but the non-ASD children yawned more when watching the video of people yawning. Explains Senju, “Our study confirms the prediction of ‘empathy theory’, by demonstrating that individuals with autism. None of this answers the question of why do we yawn in the first place? The empathy angle perhaps points to an ancient benefit in group behaviour, but what that benefit is, science does not yet know.

Why is there a “popping” sound when you crack your knuckles, and is it dangerous to crack them?

A number of reasons have been given for the characteristic “popping” sound associated with someone cracking their knuckles. One reason is that when a joint is contracted, small ligaments or muscles may pull tight and snap across the bony protuberances of the joint. Another possibility is that when the joint is pulled apart, air can pop out from between the bones, creating a vacuum that produces a popping sound. A third reason, discovered by British scientists in 1971, is that when the pressure of the synovial fluid is reduced by the slow articulation of a joint tiny gas bubbles in the fluid may burst, producing the popping sound. Research has not shown any connection between knuckle cracking and arthritis. One study found that knuckle cracking may be the cause of soft tissue damage to the joint capsule and a decrease in grip strength. The rapid, repeated stretching of the ligaments surrounding the joint is most likely the cause of damage to the soft tissue. Some researchers believe that since the bones of the hand are not fully ossified until approximately age 18, children and teenager who crack their knuckles may deform and enlarge the knuckle bones. However, most researchers believe knuckle cracking does not cause serious joint damage.

What are the stages of sleep?

Data collected from EEGs (electroencephalograms) of brain activity during sleep have shown at least four separate stages of sleep. During stage 1, heart and breathing rates decrease slightly, the eyes roll slowly from side to side, and an individual experiences a floating sensation. Stage 1 sleep is not usually classified as “true” sleep. This stage generally lasts only five minutes. Individuals awakened during stage 1 sleep will often insist that they were not sleeping, but merely “resting their eyes.” Stage 2 sleep is characterized by the appearance of short bursts of waves known as “sleep spindles” along with “K complexes,” which are high-voltage bursts that occur before and after a sleep spindle. Eyes are generally still and heart and breathing rates decrease only slightly. Sleep is not deep. Stage 3 sleep is intermediate sleep and is characterized by steady, slow breathing, a slow pulse rate, and a decline in temperature and blood pressure. Only a loud noise awakens sleepers in stage 3 sleep. Stage 4 sleep, known as oblivious sleep, is the deepest stage. It usually does not begin until about an hour after falling asleep. Brain waves become even slower, and heart and breathing rates drop to 20 or 30 percent below those in the waking state. The sleeping individual in stage 4 sleep is not awakened by external stimuli, such as noise, although an EEG will indicate that the brain acknowledges such stimuli. Stage 4 sleep continues for close to an hour, after which the sleeper will gradually drift back into stage 3 sleep, followed by stages 2 and then 1, before the cycle begins again.

What is seasonal affective disorder (SAD)?

Seasonal affective disorder is a type of depression that affects some individuals during the winter months when there is less sunlight. One hypothesis is that since there are fewer hours of daylight during the winter months, the production of melatonin is affected, resulting in physical ailments such as drowsiness and lethargy. Additional symptoms of SAD include a craving for carbohydrates, increased appetite, weight gain, and mood swings. Many researchers believe light therapy is an effective treatment for SAD. Light therapy, also called phototherapy, involves sitting near a specially designed light box that produces a strong light. Most light boxes emit a light of 2,500 to 10,000 lux, which is between the average living room lighting of 100 lux and a bright sunny day of about 100,000 lux.

Why is it difficult to remember dreams?

Almost all dreams occur during REM (rapid eye movement )sleep. Scientists do not understand why dreaming is important, one theory is that the brain is either cataloging the information it acquired during the day and discarding the data it does not want, or is creating scenarios to work through situations causing emotional distress. Regardless of its function, most people who are deprived of sleep or dreams become disoriented, unable to concentrate, and may even have hallucinations.

It appears that the content of dreams is stored in short-term memory and cannot be transferred into long-term memory unless they are somehow articulated. Sleep studies show that when individuals who believe they never dream are awakened at various intervals during the night when they are in the middle of a dream.