ISLAMABAD: Have you ever wondered why you get pins and needles?

Contrary to popular belief, it's not because lying on a limb cuts off the circulation.

In fact, it's because sitting awkwardly can trap a nerve.

And crying after being hurt is not simply an overflow of emotion, its the body's way of releasing stress hormones which build up when we're in pain.

From why our hair goes grey at the temples first, to why our heart is on the left hand side, here, experts answer the burning body-related questions you've always wanted to know...

We shiver when we're ill as it is part of the body's immune response to fight infection. The body raises its temperature in an effort to kill invading germs, and as a result we feel cold and shiver (file photo)

Shivering is usually associated with being cold, but it actually serves another purpose: it is part of the body's immune response to fight infection.

The human body runs at a fixed temperature of 37c, set by the hypothalamus area in the brain.
'When we get sick and the hypothalamus detects the immune response to microbes, it then raises the body temperature, which we feel as a fever,' explains Dr Lindsay Nicholson, a specialist in autoimmune infections at the University of Bristol.

'You feel cold because technically you are colder than the body's new set-point, and it takes time to adjust.'

Research shows that bugs do not like high temperatures, so the body appears to have learned to use heat to slow down germ growth.

Another theory is that our immune system simply works better at higher temperatures, Dr Nicholson says.

'The brain tells all cells to work harder in order to produce heat, and this includes muscle cells, which begin contracting and relaxing faster. This quick muscle movement is what we feel as shivering.'

Hair goes grey at the temples first because the cells that produce pigment are seeded in different parts of the body when the embryo forms and develops. It could be that the hair follicles in some areas, such as the temples, receive fewer pigment cells than other areas, so these will lose their colour sooner, experts said

This type of crying — in response to negative feelings or pain — is due to the connections between the tear ducts and the areas of the brain involved with emotion, says Roger Knaggs, a professor in clinical pharmacy practice at Nottingham University, who specialises in pain management.

The brain programmes these 'emotional tears' as a way to release stress hormones, which build up when we're in pain. Crying restores a normal balance.

'When we hurt ourselves, the tears released when we cry contain stress hormones, so you are literally crying away the stress,' says Professor Knaggs. 'Tears also contain endorphins, the body's natural painkillers.'

We cry after being hurt as a way to release stress hormones, which build up when we're in pain.