Why Do People Have Dreams when They Sleep?

The eyes are set within the eye sockets of the skull. They are protected in various ways, the most obvious being the eyebrows and the eyelids. Adipose tissue in the eye sockets serves as a cushioning. The lachrymal glands, or tear glands, secrete a fluid which helps to flush out foreign particles prevent infection.

They eyeball is nearly spherical and has three layers. The outermost of these is the sclera, followed the choroids and the retina.

Sclera

This layer is opaque, except for its front portion, which is transparent and thus allows light to enter. The transparent area is called the cornea. The sclera is made of fibrous connective tissue, and is thick and tough. It maintains the shape of the eyeball, and also protects the delicate parts deeper inside. The cornea is covered by the conjunction, a protective membrane which is thin and transparent. The conjunctiva extends to line the surface of the eyelids as well.

Choroids

This is a pigmented layer with a network of capillaries which supply blood to the eye. It runs along the inner surface of the sclera, but bents inwards where the cornea starts and forms a pigmented disk right behind it. This disk is the iris, the pigment of which determines the color of the eye. The iris has muscles fibers, whose movements regulate the amount of light entering the eye. At its centre is a hole, called the pupil, which allows light to pass to the lens, situated behind the iris. A part of the choroids near lens forms ciliary's processes. These too have muscle fibers, the movements of which alter the shape of the lens. In nocturnal animals, the choroid has silvery tissue that reflects light and makes he eyes sine in the dark.

Retina

This layer has two types of light receptors, called rods and cones. Rods are sensitive to dim light, while cones are sensitive to bright light and the various colors. Never fibers arising from the rods and cones go on to form the optic nerve at the back of the eyeball.

It is on the retina that the image of an object is formed. When you look at an object, rays of light from it are roughly focused by the cornea.

Dreams in the sleeping

A specific part of a person's brain called cerebrum is assigned different work like sleeping or walking. When people are engrossed in their work, nerve cells in brain, work. But when people drift into sleep, these cerebrum cells still keep on working, and hence enable men to dream of what they did during daytime. When you are sleeping, if a mosquito buzzes near your ear, you may dream of an aero plane.