2018-11-12 15:57:04 来源：网络专四专八资料下载
Those Funny Things Your Body Does
Gooseflesh, dimples, yawning — they may seem strange to you, but your body knows what its doing.
What Causes “Butterflies” in the Stomachs?
Your body is often a road map of your emotions — blushing, gooseflesh, and that quivering sensation in your stomach when youre nervous or anxious are all psychosomatic reactions. States of emotional excitability bring on muscular contractions throughout the body, resulting in generalized tension. “Butterflies” in your stomach is merely a localized tension state, caused by muscle spasms in the stomach and intestines, as well as an oversecretion of hormones from the adrenal glands. At the same time, your hands may get sweaty and your heart thump, proof again of the interconnection between the bodys systems.
Why Does Your Hair Turn Gray?
Scientists are still puzzling over this one. They know that hair colour is due to tiny pigment granules scattered along the inside of the hair shaft. They also know that these pigments are produced by cells near the hair root, and are deposited in the shaft as it forms. But researchers still dont understand the exact chemical process that takes place in the hair bulb and causes the pigment cells to stop producing colour. Most people develop noticeable gray hairs by their mid40s, although a lucky few make it to their 50s with no change in colour. Generally, blondes gray before brunettes. And, contrary to numerous ghost stories, there are no scientific data to show that hair can turn gray overnight (although rapid graying may be the result of disease). Unfortunately, the process is irreversible. Vitamins wont bring back that lost colour, either.What Is a Dimple? Its a shame that such a charming feature should have so mundane a cause, but here are the prosaic facts: The skin is attached to muscles underneath the surface, and some people have an extra point of attachment, usually on the cheek. When the facial muscles contract, they draw the skin up at that point, forming a dimple.
Why Do You Get Gooseflesh?
Remember the last time you stepped out of the shower into an airconditioned room? A chill passed over your body, leaving your skin rippled with little bumps. What happened? Once again, an instantaneous reaction took place, triggered either physiologically by the cold or psychologically by fear or stress. The autonomic nervous system called into action a group of tiny muscles, each of which is linked to one of the millions of hair shafts all over your skin surface. When these muscles, medically known as the erector pili, contract, they lift the skin and hair attached to them. This closes off the pores and blood vessels, preventing heat loss. The result: gooseflesh.
Can You Really Be “Double Jointed”?
Boasting of their prowess, kids will try to impress their friends by performing such astounding feats as twisting their thumbs backward toward their forearms, or bending their fingers into grotesque positions. But “doublejointedness” is a misnomer — its the ligaments, not the joints, that are responsible for these supple movements. Joints (“articulations,” as the medical books say) are the mooch fibrous sheaths at the end of every bone. Lined with cartilage and lubricated by the sticky fluid contained in small sacs known as bursas, joints — due to their unique construction — permit a certain amount of movement but also restrain us from moving in ways that may cause injury. Ligaments, tough but flexible ropes of fibrous tissue, hold the joints together and thus support the skeletal system. Because of their construction, some peoples ligaments stretch more than others, allowing for the increased agility that we have come to call double jointedness.
Why Do We Yawn?
Did you ever notice that when youre exhausted, drowsy, or simply bored, your breathing becomes shallow? Actually, your rate of respiration slows, too. Under normal circumstances, most people inhale and exhale 12-24 times a minute, bringing in 9-12 pints of air. But this rate can drop as low as 7 or 8 times per minute, as it does during sleep, for example. Although most people think carbon dioxide is “the bad guy” in terms of normalizing respiration (oxygen being “the good guy”) it is actually the increased amount of carbon dioxide in the bloodstream that brings our respiration rate back up to normal when it starts to slide. Nerve cells in the respiratory centre (in the brain stem just above the spinal cord) are highly sensitive to carbon dioxide. When there is too much of it in the blood, the centre signals the lungs or respiratory muscles to breathe deeper and faster. At the same time, the autonomic nervous system (which controls internal organs, muscles, and nerves without your realizing it) signals the facial muscles around the jaw to contract into a yawn, forcing you to take an extra deep breath. The combination of these two movements helps eliminate the excess carbon dioxide. You could say that yawning provides an added boost that nudges the respiratory process along.
1. What kinds of bodily activities are associatedwith anxiety?
2. Can hair graying be reversed?
3. Is “gooseflesh” a psychological or physiological phenomenon?
4. Is “doublejointed” behaviour quite abnormal?
5. Does yawning have a psychological effect on a physiological basis?