Bizarre bodily functions

From belly button fluff and pins and needles to hiccups and yawns, our bodies are host to the most bizarre phenomena - and yet, so often, there seems to be no obvious explanation. Here are some of the most common health mysteries explained

• 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!