sensory system preeti malik. structure and function sensory system consists of receptors in...
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Structure and FunctionSensory 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.
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.
Ear
Auditory or acoustic sense (hearing) is the primary function of the ear.
Helps maintain equilibrium.Three parts of the ear
ExternalMiddleInner
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.
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.
Skin
• Senses of the skin perceive touch, pressure, temperature, and pain through five specialized cells located in the skin
Meissner's corpusclesPacinian corpuscles End-bulbs of Krause Corpuscles of Ruffini Nociceptors
Assessment Techniques Sight
Ophthalmoscope Visual acuity Tonometer Color blindness chart
Hearing Otoscope Impedance testing Rinne’s test Weber's test
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
(cont…)
Astigmatism◦ A congenital defect causing imperfect curvature of the
cornea resulting in blurred visionCataract
◦ Clouding of the lens that causes blurred or partial vision
Conjunctivitis ◦ Also called pink eye, is a bacterial or viral
inflammation of the eyelid
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(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
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(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
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(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 eyeNight blindness
◦Poor vision in dim light that results from a deficiency in the rods of the retina
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(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
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(cont…)
Rhinitis Inflammation of the lining of the nose caused by
allergic reaction, viral infection, sinusitis, or chemical irritants
Ruptured eardrumResults 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