- Pins and needles
- Body jerks
- Twitching eyes
- Contagious yawns
- Synchronised periods
- Earwax
- Passing wind
- Belly button fluff
What are pins and needles?
Everyone has experienced that sharp tingling sensation in the toes, legs or fingers at some time or another. Pins and needles, or paraesthesiae, as they are known, generally come about due to pressure on a nerve that is close to the skin surface. Common pins and needles 'hot spots' include the elbow, when the 'funny bone' nerve is subjected to pressure, and the calf or foot from pressure on the nerve below the knee.
In the same way, when, for example, we stand up after sitting in a particular position for a long time and our legs appear to have 'gone to sleep', this is the result of a nerve being compressed and then bouncing back into shape.
Why does my body jerk when I am falling asleep?
Ever been just about to drift off into a blissfully deep sleep when suddenly you feel like you are falling, and your body jerks in shock? What you have experienced is called a 'hypnic jerk'. This is an involuntary muscle twitch, which is most likely to happen if you are exhausted or sleeping uncomfortably. It occurs during very light sleep, when your body temperature drops - your heart slows down and your conscious brain gradually relinquishes control of your muscles. This muscle relaxation is misinterpreted by the brain as falling, or toppling over, and by reflex, the body jerks the limbs out to stay upright, whilst another part of your brain invents a 'mini-dream' in which you are falling off a cliff, for example. So, next time you wake up with a 'sleep start', just remember it's simply your body's way of telling your muscles to chill out!
What cause a twitching eye?
While we're on the subject of twitching, you may wonder why your eye sometimes twitches (or perhaps you're more concerned about it being noticeable to others). The twitch itself occurs due to the repetitive contracting and relaxing of the muscle below the eye as it is stimulated by a repetitive electrical impulse from a nerve. But as to why the nerve should fire in this way when we are tired or stressed remains a mystery.
Why are yawns contagious?
Whether it's laughing or yawning, human bodies seem to have an amazing capacity for infectious behaviour. But why is it that, when we yawn, the world tends to yawn with us? The traditional explanation for yawning is as the result of reduced oxygen levels in the brain but newer theories claim that it is a trigger for changes in 'brain state' in preparation for a demanding activity such as a marathon or exam.
Why yawning should be so infectious is harder to pin down - the evolutionary explanation seems to be that collective yawning acts as warning or signal. So, if you step out of today's stuffy boardroom meeting and back into the shoes of primitive man, you would wake up and infect other members of your group with your loud yawn and then go out to hunt wild animals!
Why do we all have our periods at the same time in the office?
Another bizarre infectious phenomenon which deserves a brief mention is 'synchronous menstruation', when women living or working together find that their periods come at the same time. Although this is still a grey area, research suggests that it is caused by pheromones and scent.
What is the point of earwax?
You may ask if we really need to produce something as unattractive and seemingly unnecessary as earwax. Earwax is produced by tiny glands in the outer part of the ear and is vital for catching particles of dust and for getting rid of tiny bacteria too. Tiny hairs in the outer ear move the wax to the outside so that the ear canal is kept clean and the eardrum is protected. The sticky brown wax that comes out of our ears is in fact a medley of dead bacteria and skin cells, debris and dust.
Why do we pass wind?
And now for one of the less attractive bodily emissions: gas. Well, given that our bodies are like 24-hour factories, constantly processing air, liquids and foods, it's hardly surprising that we produce a by-product or two. In fact, on average, we pass wind 15 times a day, and it is normal to produce up to three and half milk bottles' worth of wind daily! But have you ever wondered why it is that eating beans, cabbage, broccoli, curry and beer can result in smells that could only be described as rotten eggs? The culprits: smelly substances like hydrogen sulphide that are produced when food is broken down in the colon.
As for those sometimes embarrassing and inopportune tummy rumblings, they are produced when the liquid and gas contents of the intestine are shunted back and forth by contractions of the gut. They can be the product of hunger, anxiety, fright and, yes, unfortunately for us, sexual excitement!
What on earth is belly button fluff?
Ok, so last but not least, why do we get those strange little bits of bluish fluff in our navels? Believe it or not, in 2002, a University of Sydney researcher won the 'Ig Nobel Prize' (the spoof Nobel prize for dubious contributions to scientific research) for his investigation into the cause of tummy-button fluff, in which he examined the fluff samples of 5000 people! His conclusion was that the fluff is made up of clothing fibres and skin cells that are led to the tummy-button via body hair.