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Unit 8: The Senses
Amy J. Hilbelink, Ph.D.
Tracy Abram, MAIS, BS
The Senses
Objectives
• Classify sense organs as special or
general. Discuss their functions.
• Discuss how a stimulus is converted into a
sensation.
• List major senses
• Describe eye and ear anatomy
• Describe major visual disorders and
hearing impairment
Classify sense organs as special or
general
•
•
•
•
•
Special:
Eye
Taste buds
Ear
Nose
• General:
• Microscopic receptors
– Pacinian corpuscles
– Meissner’s corpuscles
– Muscle spindles
Inquiring Minds want to know…
• What is the difference between
special and general sense
organs?
All About the “Special”
• Special = they have large and complex
organs or localized groupings of
specialized receptors like taste buds on
tongue.
• These are the senses that you typically
think of; except for perhaps touch!
All About the “General”
• General = made of microscopic receptors
widely distributed throughout the body.
– Pacinian corpuscles = pressure and high
frequency
– Meissner’s corpuscles = fine touch and low
frequency
– Muscle spindles = propriocetors (muscle
length and location)
Sense organ functions
•
•
•
•
•
Vision
Hearing
Smell
Taste
Balance
Eye anatomy
• Sclera = white of the eye (cornea)
• Choroid = contains a dark pigment to prevent scattering
of light rays
• Retina = innermost layer of eyeball (rods and comes)
• Iris = circular colored part of eye
• Conjunctiva = mucous membrane that lines eyelids and
covers the sclera
• Lacrimal gland = tear duct
• Pupil = black center of iris; a hole
• Lens = ciliary muscles contract the lens for focusing
My Eye Exam 2011
Prof. Abram’s Left Eye
Prof. Abram’s Right Eye
Prof. Abram OTC Scan
Major visual disorders
• Refraction disorders
– Myopia = nearsightedness
• Astigmatism = irregularity in cornea or lens
• Conjunctivitis = pink eye
• Strabismus = convergent
How is a stimulus converted into a
sensation?
Stimulus detected
[sound]
Stimulus converted to
electrical signal or nerve
impulse= [middle ear]
Signal transmitted over
nervous system “pathway”
= [VIII cranial nerve]
Sensation perceived
in brain = [music]
Ear anatomy
• External ear
– External auditory canal
– Tympanic membrane
– eardrum
Ear anatomy
• Middle ear
– Ear bones = ossicles
• Malleus
• Incus
• stapes
– Auditory or Eustachian tube
Ear anatomy
• Inner ear
– Bony labrinth
– Perilymph
– Vestibule
– Semicircular canals
– Cochlea
– Crista ampullaris
– Organ of Corti
Hearing impairment
• Blockage of external auditory canal
• Otosclerosis = structural irregularities in
stapes
• Tinnitus = ringing in ears (may be
symptom of otosclerosis)
• Otitis = ear infection
• Meniere’s disease = chronic inner ear
disease, resulting in vertigo
Which one would be
the worst to lose?