Preeti Malik

 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.

 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.

 Auditory or acoustic sense (hearing) is the primary function of the ear.
 Helps maintain equilibrium.
 Three parts of the ear

External

Middle

Inner

 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.

 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.

Figure -3 Nose and Surrounding
Structures

•
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

 Sight

Ophthalmoscope

Visual acuity
 Tonometer
 Color blindness chart
 Hearing

Otoscope

Impedance testing
 Rinne’s test

Weber's test

 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

(cont…)
 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

(cont…)
 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
Copyright 2003 by Mosby, Inc. All rights reserved.

(cont…)
 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
Copyright 2003 by Mosby, Inc. All rights reserved.

(cont…)

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
Copyright 2003 by Mosby, Inc. All rights reserved.

(cont…)
 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
Copyright 2003 by Mosby, Inc. All rights reserved.

(cont…)
 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
Copyright 2003 by Mosby, Inc. All rights reserved.

(cont…)
 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
Copyright 2003 by Mosby, Inc. All rights reserved.

 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.