1. CHAPTER 19 SENSORY SYSTEM
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2. Structure and Function
Sensory system consists of receptors in specialized cells and organs that perceive changes in the internal and external environment
The stimuli cause nerve impulses that are sent to the brain for interpretation
Environmental stimuli are perceived with the senses of vision, hearing, touch, taste, position, and balance
Copyright 2003 by Mosby, Inc. All rights reserved.

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Eye
The most important sensory organ because 90% of the information about the environment reaches the brain from the eyes
Movement of the eye is controlled by the extrinsic muscles
Only one fifth of the eye is actually exposed to the environment
Copyright 2003 by Mosby, Inc. All rights reserved.

4. Figure 19-1 Structures of the Eye
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Ear
Auditory or acoustic sense (hearing) is the primary function of the ear
Helps maintain equilibrium
Three parts of the ear
External
Middle
Inner
Copyright 2003 by Mosby, Inc. All rights reserved.

6. Figure 19-3 Structures of the Ear
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Tongue
Taste, or the gustatory sense, is perceived by specialized cells located in papillae on the tongue called taste buds
Flavor is identified by smell as well as taste
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Nose
Olfactory sense originates in olfactory receptor cells in the nose that immediately transmit impulses to the brain through the olfactory cranial nerves
Nasal cavity is divided into two sections by the septum
Olfactory receptor neurons are stimulated by chemicals (gases) in the air
Smells can reduce stress, affect blood pressure, recall memories, and aid in the sense of taste
Copyright 2003 by Mosby, Inc. All rights reserved.

9. Figure 19-5 Nose and Surrounding Structures
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Skin
• Senses of the skin perceive touch, pressure, temperature, and pain through five specialized cells located in the skin
Meissner's corpuscles
Pacinian corpuscles
End-bulbs of Krause
Corpuscles of Ruffini
Nociceptors
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11. Assessment Techniques
Sight
Ophthalmoscope
Visual acuity
Tonometer
Color blindness chart
Hearing
Otoscope
Impedance testing
Rinne’s test
Weber's test
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12. Disorders of the Sensory System
Achromatism
Called color blindness, is a common inherited defect
Amblyopia
Also called “lazy eye,” is poor vision in one eye often resulting from better vision in the other eye during infancy or early childhood
Anacusis
Hearing loss resulting from damage to neural tissues
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13. Disorders of the Sensory System (continued)
Astigmatism
A congenital defect causing imperfect curvature of the cornea resulting in blurred vision
Cataract
Clouding of the lens that causes blurred or partial vision
Conjunctivitis
Also called pink eye, is a bacterial or viral inflammation of the eyelid
Copyright 2003 by Mosby, Inc. All rights reserved.

14. Disorders of the Sensory System (continued)
Diabetic retinopathy
Condition of damaged blood vessels in the retina caused by uncontrolled diabetes mellitus
Diplopia
Or double vision, results from muscle imbalance or paralysis of an extraocular muscle
Epistaxis
Nosebleed resulting from disease, trauma, or other conditions such as hypertension, leukemia, or rheumatic fever
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15. Disorders of the Sensory System (continued)
Glaucoma
An increase in the pressure inside the eye, caused by trauma or hereditary factors
Hyperopia
Farsightedness resulting from a congenital deformity in the eye
Macular degeneration
A slow or sudden painless loss of central vision
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16. Disorders of the Sensory System (continued)
Meniere’s disease
A collection of fluid in the labyrinth of the ear leading to dizziness, ringing in the ear or tinnitus, pressure, and eventual deafness
Myopia
Nearsightedness resulting from a congenital deformity in the eye
Night blindness
Poor vision in dim light that results from a deficiency in the rods of the retina
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17. Disorders of the Sensory System (continued)
Otitis media
A middle ear bacterial or viral infection common in young children
Presbyopia
A type of farsightedness related to aging
Retinal detachment
Due to injury or uncontrolled diabetes mellitus
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18. Disorders of the Sensory System (continued)
Rhinitis
Inflammation of the lining of the nose caused by allergic reaction, viral infection, sinusitis, or chemical irritants
Ruptured eardrum
Results from infection, an explosion, a blow to the head, or a sharp object inserted into the ear
Sinusitis
A chronic or acute inflammation of the cranium
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19. Disorders of the Sensory System (continued)
Strabismus
A condition in which both eyes do not focus on the same point or direction
Stye
Bacterial infection of the sebaceous glands of the eyelid
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20. Issues and Innovations
Visual correction by surgery
– Radial keratotomy
– Epikeratophakia
– Photorefractive keratectomy (laser surgery)
• Noise pollution
– Inner ear damage is permanent
– Loud music and phones can cause hearing loss
Copyright 2003 by Mosby, Inc. All rights reserved.