* One of the basic processes in the interaction of man and his environment that governs the reception of information. * Man must be able to sense, interpret, and respond to various events and stimulations. The study of reception and function of stimulation may be divided into two parts: * Sensation – considers the mechanism of receiving information * Perception – considers the received information and past experiences. SENSATION
* Sensations that can be relayed or discriminations it can make to adjust its behavior according to the sensory messages it receives. * There are two factors which are necessary for sensation to occur: * There must be stimulus.
* There must be receptors that are sensitive to the stimulus. According to Kagan, a stimulus is any form of energy capable of exciting the nervous system like light waves, sound waves and the chemical energy that causes the sensation of taste and smell. The receptor is a specialized nerve ending capable of responding to energy. The mechanism that converts stimulus energy into neural energy are called the senses. There are five primary senses:
* Skin senses
In addition we have:
* The sense of equilibrium
* Organic sense
* Sense organ of vision
* Sense of sight
* Arranged like a camera to focus on light reflected from or generated by objects outside the body onto a sheet of receptor cells. * Sense objects and then convey the information to the brain. * Visual perception takes place
* The stimulus for vision comes in the form of electromagnetic waves.
Structure of the eye
3 Coats of an Eye
Sclera- outer coat
Choroid Coat- middle layer
* Tough opaque layer of connective tissue used to protect the inner structures of the eye. * Helps maintain the shape of the eyeball.
* In front, this layer becomes the cornea which is thin and transparent. It gathers the light rays to enable them to pass through the pupil. Choroid Coat
* Pigment layer
* Contains some of the blood vessels that supply the eye with blood. * Absorbs imperfectly focused light rays.
In the front part of the eye, it becomes modified to form the iris and the ciliary body. Pupil
* The central opening of the iris.
* Behind the pupil lies the crystalline lens, the shape of which is controlled by the ciliary muscles. Iris
* A circular arrangement of muscles that contract and expand to change the size of the pupil depending upon the amount and intensity of illumination in a process called light or dark adaptation. * The color of the eye is due to the pigments in the iris. Lens
* The lens become thinner to bring faraway objects into focus and thickens to focus on nearby objects. This process is called accommodation. * The lens focuses the light rays to the retina.
* Contains approximately 115,000,000 rods and 6,500,00 cones. These are light sensitive cells and are the receptors in the eye. Rods
* Shaped like cylinders. Function chiefly under conditions of low illumination and send information to the brain about movement and about white, gray, and black but not about color. Cones
* Conical or tapered in shape. Function in bright light and provide information not only about movement and about the black and white dimension but also about color. Fovea
* The most sensitive part of the retina which contains only cones tightly packed together. Blind Spot
* The region of the retina where there are no rods and cones. The human eye
The inside cavity of the eyeball is filled with a transparent substance called the Vitreous humor The space between the cornea and the iris is filled with the Aqueous humor Each eyeball is attached to the eye socket by six eye muscles that enable us to look up, down, and sideways. How we...