Receptor Organs

The survival of animals depends on their ability to compute all the
information flowing from the environment and integrate them into meaningful
instructions to the effector organs. Information relating to the external and
internal environment can be gained only through the sensory receptor
organs.

These organs have specialized cells that can transform the stimuli
falling on them, whether it is chemical, radiant, electrical or mechanical, into
electrical signals and convey the same to the central nervous system. In the
CNS the integration and coordination of the data happens.

This ability of the sensory cells is known as transduction and the receptors are sometimes referred to as transducers. (Receptor Organs)

Eye – Receptor Organs

The visual system gives information about size, shape, color,
luminosity and movements of object in the external world. (a) Focusing Mechanism in the Human Eye Light rays entering the eye are redirected or refracted. Refraction occurs through three surface of the eye before the light reaches the retina.

The first of the refracting surfaces is the cornea, then the front surface of the
lens and finally the rear surface of the lens. Between the cornea and the lens is a colourless, watery fluid called aqueous humour. At the back of the eye between the lens and the retina is the vitreous humour made of a gelatinus mucoprotein.

The humours are transparent so that transmissions of light through the cavities of the eye to the retina is not normally impeded. Human eye has a lens apparatus whose convexity can be adjusted for focusing near and distant objects. This ability of the eyes to focus objects at varying distances is called ACCOMMODATION. (Receptor Organs)

The accommodation is achieved due to suspensory ligament, ciliary muscle and ciliary body. When a normal eye is looking at a distant object, the ciliary muscles is fully relaxed and parallel rays from the object come to focus on the retina.

Hence a clear image is seen. When the object is brought close to the eye the
refractive power of the eye is increased by the process of accommodation.
The increase in refractive power is the result of an increase in the curvature
of the anterior surface of the lens. This avoids the blurred image for a closer
object. (Receptor Organs)

Similar accommodation happens for viewing a distant object by stretching the suspensory ligament attached to the lens. This act alters the contour of the lens.

Receptor Organs

Eye – Receptor Organs

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