Processing Information: Vision and Hearing

In order for our nervous system to receive information, there must be a stimulus and an appropriate receptor. For example, shining a light in someone’s ear produces no response because there is no light receptor in the ear. The message is then interpreted by the Central Nervous System.

Vision

This is the sense with the largest part of the brain devoted to it in humans. Impulses must be received by the visual center in the cerebral cortex or else we are blind. The eyes are contained in orbital cavities for protection. They are also set in fat to cushion them. Prolonged sickness can deplete this fat resulting in a sunken look to the eyes.

Vision continued…

Eyes have muscles both inside and outside. The muscles inside the eye control the lens and iris. The muscles on the outside move the eye in its socket. The eyes are well protected by the eyebrows, eyelids, and the eyelashes.

Hearing

The ear actually has two jobs. It converts sound waves into nerve impulses, and it acts as the organ of balance.

The structure of the ear actually occurs in three parts:

- the external ear- the middle ear- the inner ear

Structure of the Ear

External Ear: This is the part of the ear visible on the

head. The auricle (or pinna) acts as a funnel to direct sound into your auditory canal. The auditory canal passes into the skull.

Ear continued…

Middle Ear:The inner end of the auditory canal is covered

by the tympanic membrane (eardrum). The middle ear contains 3 tiny bones (hammer, anvil and stirrup) which convert vibrations into nerve impulses. The middle ear also contains the Eustachian tube (connected to throat) to equalize the pressure in the ear.

Ear continued 2…

Inner Ear:The inner ear has two functions. The

first is to conduct nerve impulses to the brain by way of the auditory nerve. The second is to maintain balance through the utricle, saccule, and the semi-circular canals.