Читать книгу Sleep: The secret to sleeping well and waking refreshed - Prof. Idzikowski Chris - Страница 79

Light and the retina

The retina consists of receptors that are sensitive to light. One group known as the ganglion cells are particularly sensitive to light, and in particular to blue light (such as that of the sky). These cells make a direct connection to the biological clock (see page 14) which controls the time that we are likely to sleep. About 20 per cent of light gets through the eyelids when the eyes are shut, which means that we can be affected by light and the time that we sleep even when we are in bed with our eyes shut!