Why do I see dots of light when I close my eyes?

  Even if there is no external light source to stimulate, when we close our eyes, we will see flickering lights, this phenomenon is called “phosphenes”, commonly known as “intraocular flashes”. Almost everyone has had this experience, which is the instantaneous light sensation generated by mechanical stimulation, electrical stimulation, etc. in the retina. In our eyeballs, retinal ganglion cells are responsible for receiving visual information from photoreceptor cells in the retina and transmitting it to the brain. Retinal ganglion cells cannot distinguish between stimuli, and rubbing the eye can “trick” them into “wake up” in a light-activated-like manner, sending the stimulus to the cerebral cortex. In addition, phosphenes can also occur in the dark when the eyeball moves sharply, back and forth pressure, rapid adjustment or sneezing, but it is not the direct mechanical stimulation of the retinal photoreceptor layer. In many cases, phosphenes can be regarded as mechanical retinal elongation. and secondary processes arising from changes in blood circulation.
  Why do babies cry when they are born? Most of the
  fetuses in the womb exchange substances with the mother through the placenta. After birth, the baby must rely on its own breathing to inhale oxygen and expel carbon dioxide. There is no air in the lungs of a fetus, and the lungs are still solid tissue. After the baby is born, because the body is no longer curled into a ball, the originally contracted thorax suddenly expands, the chest cavity immediately expands, and the lung lobes also open, and the first breath of air is inhaled at this time. The air enters the alveoli from the trachea, the inspiratory muscles immediately relax, the expiratory muscles contract immediately, and the thorax shrinks to its original size, forcing the air out of the lungs. When the exhaled gas passes through the larynx, the larynx muscles contract, the two vocal cords in the larynx are pulled closer together, the gas impacts the vocal cords, and the vocal cords vibrate, making a cry similar to crying.
  When the baby is just born, the amount of carbon dioxide in the blood is large, which will stimulate the respiratory center and strengthen the breathing, so they all breathe in big mouths. Therefore, every baby has to cry like this for a while after birth, and when the breathing activity has established a normal rhythm, it will stop crying like this.
  Why chameleons are good at changing colors
  The chameleon has no fixed color. When it guards in the grass or on the branches to catch prey, the color of its body surface becomes close to the color of the grass and leaves. When it crawls on the ground, it turns into a color similar to the soil. It changes like this, one is to facilitate predation, and the other is to protect itself. The chameleon’s body color is generally emerald green at night, and after dawn, when the temperature reaches 25 ℃, it will turn dark green again.
  The reason why a chameleon can change body color is mainly because its central nervous system can transmit the stimulation of light to the pigment cells in the body after its eyes are stimulated by external light. At this time, what color the chameleon sees, the surface of the body will become what color. There are many factors why a chameleon can change its body color. Not only the intensity of light can change its body color, but even its emotional changes will also change its body color. Once the chameleon’s central nervous system is severed, it can no longer change its body color. From this point of view, the chameleon’s ability to change color is mainly determined by the nervous system.
  Why the lotus “emerges from the silt without staining?” The
  lotus is one of the top ten famous flowers in China. They “come out of the mud without being stained, and they are clean without being a demon”, and they are a symbol of nobleness and purity in people’s hearts. So, why can lotus flowers and lotus leaves “get out of the mud without being stained”? It turned out that this was related to the special microstructure of their surfaces. There are many tiny papillae-like protrusions on their outer layer, and the protrusions are filled with air, blocking the infiltration of muddy water. When their leaf buds and flower buds are drawn from the sludge, it is difficult for the muddy water to get on them because their surface is protected. Even if there is a small amount of sludge on the leaf buds or flower buds, they will be washed away by the turbulent water waves. When they come out of the water, they will naturally be clean and lovely.
  Why do color photos fade over time
  ? Most of the color dyes in color photos are organic molecules with more complex structures. Their properties are relatively lively, and they will decompose when exposed to strong sunlight and humid and hot environments. Therefore, once stored improperly, the color photos will be faded. In addition, if the color photo encounters some strong oxidizing chemical reagents, it will also promote the decomposition of the dye on the color photo, thereby causing the color photo to fade.
  Color photos also sometimes exhibit color casts. This is because the dyes on color photos are composed of 3 different colors of dyes, and these 3 dyes will fade to different degrees under the same light or the same chemical agent. Therefore, as soon as some colors change, color casts appear in color photos.
  Why does altitude sickness not occur when flying?
  Many people who have climbed high mountains or have been to high altitudes have experienced altitude sickness, which is a very uncomfortable feeling, mainly manifested as headache, insomnia, loss of appetite, fatigue, and difficulty breathing. People who usually live in the plains or the seaside are prone to altitude sickness when they enter the plateau above 3,000 meters above sea level. This is because the air pressure is higher in the low-lying places such as the plains and the seaside. It is equivalent to being exposed to a low-pressure and low-oxygen environment, and the various functions of the body are not adapted to that environment, and altitude sickness will occur.
  However, when we take a plane, the plane can fly to an altitude of 10,000 meters, which is higher than the Qinghai-Tibet Plateau and Mount Everest. Why haven’t we heard of altitude sickness on the plane? The reason is actually quite simple. Because the cabin of the aircraft is closed, the air pressure in the cabin is maintained at 0.6 to 0.8 atmospheres, which is basically the same as our air pressure in the plains. In this way, people in the plane will not suffer from altitude sickness due to the low air pressure outside the cabin.
  waterfalls There are many reasons for the formation of waterfalls, mainly including the following: Due to the movement of the earth’s crust, a very steep rock wall has been formed. The water forms a lake, and the lake overflows; the magma ejected by the volcano or the landslide caused by the earthquake blocks the river channel and forms a natural dam; in the river, the hard rocks are not easily eroded, and the soft rocks are easily eroded, resulting in The difference in the topography of the river bottom, after the ancient glacier “U”-shaped valley is occupied by the river, the water flow will also flow in the valley with great difference in depth; at the point where the river enters the sea, if the coast is destroyed quickly, the original high The bottom of the river that goes out to the sea will be “suspended” on the coast; where the dark river flows in the limestone area, the topography will change suddenly, or the dark river will flow from the steep cliff. For these reasons, waterfalls can be formed.
  Why can’t you see seeds in bananas?
  This is because the bananas we eat now are improved after a long period of artificial selection and cultivation. It turned out that wild bananas also had very hard seeds, which were very inconvenient to eat. Later, under artificial cultivation and selection, wild bananas gradually developed in the direction people hoped. Over time, they changed the nature of hard seeds, and gradually formed triploids, while triploid plants are seedless. Strictly speaking, the bananas we usually eat are not without seeds. When we eat bananas, we can see rows of brown dots in the pulp, which are the seeds, but they are not fully developed and degenerate into this shape. Triploid bananas have no seeds, so how do they reproduce? Nowadays, bananas are generally propagated by underground root tillers, which do not use seeds.

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