Transcript Chapter 8 Notes Senses

Special Senses
Anatomy and Physiology
Introduction

Senses are classified in two major groups:
A. Special – senses of smell, taste, sight,
hearing, and balance
B. General – touch, pressure, pain,
temperature, itch, and proprioception
(position of the body and its various
parts)
Anatomy of the Eye
Adult eye is sphere – 1 inch in diameter
 Accessory structures: extrinsic eye
muscles, eyelids, conjunctiva, lacrimal
apparatus
 Eyes protected by eyelids
 Corners are:
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 Medial
canthus
 Lateral canthus
Anatomy of the Eye Cont.
Meibomian glands – sebacious glands
produce oily secretions - lubricates eye
 Ciliary gland – modified sweat glandbetween eyelashes
 Conjunctiva – membrane - lines eyelid;
covers part of outer surface
 Conjunctivitis –red eyes, irritation, Pink
eye –bacteria or virus – highly contagious
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Anatomy of the Eye
Anatomy of the Eye Cont.
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Lacrimal apparatus – gland and ducts
drain lacrimal secretions into nasal cavity
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Lacrimal glands –Tears flush eyeball

Lysozyme – enzyme that destroys
bacteria
Internal Structure of Eye
 Eye
is hollow
sphere
 wall composed of
three tunics or
coats
 Interior filled with
fluid called humors
– maintains shape
of eye
Tunics of Eyes
1. Sclera – outermost tunic –
protection – white of eye
A. cornea – transparent –
light enters
–no blood vessels
-can be transplanted
–not a tunic
Tunics of the Eye cont.
2. Choroid – middle tunic – blood
rich and dark pigment
A. Ciliary body – smooth muscle structure
– lens and iris are attached
B. Iris – pigmented portion – eye color
-has muscles to regulate light.
C. Pupil - in iris – light passes
Pupil
 Close
Vision and Bright light –
circular muscles contract and pupil
constricts allowing less light in
 Distant
Vision and Dim light – radial
fibers contract enlarges pupil (dilate)
allows more light in
Tunics of the Eye Cont.
3. Retina – innermost tunic – contains
millions of receptor cells –rods and cones
Rods and cones -photoreceptors
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– nerve impulses transmitted to optic nerve
Rods - see gray and peripheral vision
Cones - allows us to see color
no rods or cones on optic nerve where it
leaves the eye –called blind spot or
optic disk
Inside View

When a doctor
looks at the back
of your eye,
here's the view:
Visual problems
 Night
blindness – vit A deficiency –
deteriorates neural retina – rods
 Color
blindness – lacks one or
more cones – common red-green –
sex linked trait – found on X
chromosomes – most always in
males
Cont.
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Cataracts – vision is hazy – cause blindness –
surgically remove lens
Glaucoma – pressure within eye – build up of
aqueous humor – causes pain, blindness in older
people
Myopia – nearsightedness – distant objects
blurry – eyeball too long
Emmetropia – good vision
Hyperopia – farsightedness – eyeball too short –
distant objects are clear - p. 283
Eye Muscles
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Six muscles control the movements
of eye.
Lateral rectus - moves eye
laterally
Medial rectus - moves eye
medially
Superior rectus - elevates eye
Inferior rectus - depresses eye
Inferior oblique - rotates eye
Superior oblique - rotates eye
Ch. 8
Day 2
The Ear – External Ear
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Auricle – fleshy partexternal ear
Auricle opens into
external auditory
meatus –leads to
eardrum
Auricle directs sound
waves toward external
auditory meatus
External Ear Cont.
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Meatus lined with hairs and ceruminous
glands – EAR WAX
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Eardrum – called tympanic membrane
– thin membrane, separates external from
middle ear. Sound waves cause eardrum
to vibrate.
Middle Ear
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The middle ear contains three auditory ossicles –
ear bones
Malleus – hammer
Incus – anvil
Stapes – stirrup
Eustachian tube – enables equalization of air
pressure b/w outside and middle ear cavity.
Changing altitude causes pain.
 swallow, yawn, chew, or hold nose to force air
out of lungs
Inner Ear
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Tunnels called bony
labyrinth – maze – has
fluid called perilymph
Inner ear has three
parts
Cochlea – hearing
Vestibule – between
Cochlea & Semicircular
canal
Semicircular Canalbalance
Steps involved in Hearing – Test
Question
Sound waves collected by auricle and
conducted through external auditory
meatus to tympanic membrane,
causing vibrations
 Vibrating tympanic membrane causes
malleus, incus, and stapes to vibrate
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Steps involved in hearing Cont.
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Vibration of stapes produces vibration in
perilymph of scala vestibuli
Causes vibration in cochlea
Vibration detected by hair cells which induce
action potential in cochlear neurons
Action potentials conducted to CNS
Perceived as SOUND by cerebral cortex
Day 3
Taste and Smell
Taste and Smell
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Chemoreceptors –taste
and olfaction(smell)
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Taste buds – 10,000 on
tongue – few on soft
palate and cheeks
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Papillae – peglike– where
taste buds are on tongue
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Four basic types – sweet,
sour, bitter, salty
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Factors that affect taste –
olfactory– congestion –
temperature - texture
The Tongue
Dorsal surface
covered with small
projections, or
papillae.
 4 types of papillae:
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Fungiform
Filiform
Circumvallate
Foliate
FYI
 Older
adults often prefer highly
seasoned foods. (Why??)
 Mid-40s – diminished ability to
taste and smell (fewer receptor
cells)
 Half of people over 80 have
poor taste and cannot smell at
all.
Geographic Tongue
Some
papillae fall off
–Map-like, geographic appearance
–Only symptom in most cases
Sometimes
painful
–Sensitivity to hot and spicy foods
No
cure – heals by itself
No
known cause
–Can happen to anyone!
Geographic tongue
Taste Buds
Sweet – tip
 Salty – anterior
sides
 Sour – posterior
sides
 Bitter – back
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BUT…
Taste Buds Cont.
 Only
slight differences in
locations of taste receptors.
 Most
taste buds respond to two
or more types of taste.