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Sunday, September 4, 2011

Sense Organs: The Eye And The Ear -- Lesson 260

In the recent chapters we have learned about the sense organs; the eye and the ear. Now in this chapter we would learn about in brief and recall the points.The sensitive nerve endings in the corium layer of the skin receive impulses from stimuli of various kinds and applied to the external surfaces of the body. These nerve endings transmit electrical messages, initiated by the stimuli, to regions of the brain (cerebrum and thalamus) so that we can able to identify sensations through temperature, touch, pain, and pressure. The nerve cells which carry impulses from a sense organ or sensory receptor area, such as the skin, tastebuds, and olfactory regions which are also called centers of smell in the nose, to the brain are called afferent sensory neurons.

We already came across through the eye and the ear which are the sensory organs, like the skin, taste buds, and olfactory regions. Because these are receptors, whose sensitive cells may be activated by certain form of enrgy or stimulus by starting a series of nerve impulses along afferent sensory neurons that lead to the brain.
The kind of stimulus is applied to a particular receptor, the sensation we felt is identified by the regions in the brain that are connected to that receptor.

Thus, mechanical injury that might stimulate receptor cells in the eye and the ear would produce sensations of vision also called flashes of light adn sound. In the same way, if one could make a nerve connection between the sensitive receptor cells of the ear and the area in the brain associated with sight, it would be possible to perceive, or "see," sounds. We can realize the general pattern of events when such stimuli as light and sound are applied to sense organs such as the eye and ear.

Stimulus (applied to) Receptor cells in ear and eye (which excited to ) afferent nerve fibers (which carry impulse to) brain where nerve impulses are translated into sound sensations and visual images.

In the next chapter we would learn about the anatomy and the physiology of the eye.

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