Transcript vision, proprioception, touch, taste, smell, and hearing.

McGraw-Hill/Irwin
© 2012 McGraw-Hill Companies. All Rights Reserved.
The communicative link between the human organism and the
environment is in part made possible by the senses: vision,
proprioception, touch, taste, smell, and hearing.
9-2
Understanding the
Mechanics of Vision
Light rays converge and meet at a focal point
The cornea and the fluids in the eye refract (bend)
the light rays
The lens can adjust the focal point by changing
shape
Relaxation of the ciliary muscles causes the lens to
flatten
Contraction of the ciliary muscles causes the lens
to become more spherical
9-3
Understanding the
Mechanics of Vision
Accommodation is the adjustment of the eye to
variations in distance
The retina contains two photoreceptors
Rods are responsible for vision in low illumination
(night vision)
Cones are responsible for color vision and visual
acuity
9-4
Understanding the
Mechanics of Vision
Macula lutea: an oval yellow spot at the center of
the retina
Fovea centralis (point of best vision) is located here
Cone cells are concentrated
There is an absence of rod cells
9-5
Retina
9-6
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9-7
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7
Understanding the
Mechanics of Vision
9-8
Physical Development
of the Eye
The eye develops as an outgrowth of the forebrain
Part of the central nervous system
6 cranial nerves govern vision
At birth
The eye is hyperopic (light focuses behind the
retina)
The retina contains mostly rod cells
9-9
At birth
9-10
Physical Development of the Eye
At 1 month postnatal
Cone cells appear
At 8 months postnatal
Macula is mature
9-11
Development of Selected Visual Traits
and Skilled Motor Performance
9-12
Visual Acuity
Static visual acuity
Target and performer are stationary
20/20 vision means that you see at 20 ft. what a
person with normal vision sees at 20 ft.
20/100 means that you see at 20 ft. what a
person with normal vision sees at 100 ft.
9-13
Visual Acuity
Degree of detail that
can be seen in an
object
A Snellen eye chart is
used to determine
visual acuity
9-14
Visual Acuity
This Snellen eye chart
is used with children in
grades K-1 who may
not be capable of
letter recognition
9-15
Visual Acuity
Birth
6 months
1 yr.
4-5 yr.
20/200 and
20/400
20/200
20/50
20/20
9-16
Visual Acuity
Dynamic visual acuity
Ability to see the detail in moving objects
Ability of the central nervous system to estimate an
object’s direction
Ability of the ocular-motor system “to catch” and
“to hold” an object’s image on the eye’s fovea long
enough to see detail
9-17
Visual Acuity and Motor Performance
Both static and dynamic visual acuity play keys
roles
Dynamic visual acuity is highly correlated with
success in
Free throw shooting
Ball catching
9-18
Visual Acuity and Exercise
Aerobic activities appear to improve visual acuity
for up to two hours post-exercise
Increase in acuity due to increase in blood flow
and oxygenation to the eye
9-19
Visual Acuity and Aging
Age-related eye
diseases (ARED) are
the leading cause of
loss of visual acuity
Conditions/diseases
Age-related macular
degeneration
Glaucoma
Cataracts
Senile miosis
Diabetic retinopathy
Presbyopia
9-20
AREDs
Age-related macular degeneration (AMD)
Loss of central vision
Dry form
Breakdown of light sensitive cells in the macula
Central vision affected
Not allowed to drive and will have trouble reading
No problem with general movement
Wet form
New blood vessels form behind the retina, leak, and
destroy the macula
9-21
AREDs
Normal
AMD
Amsler Grid
9-22
AREDs
Glaucoma
Leading cause of
loss in visual acuity
and blindness
High pressure in
eye
Loss of peripheral
vision
Eventual loss of
central vision
9-23
AREDs
Cataracts
Clouding of the eye’s lens
Initial symptoms include
complaints of glare, colors
that seem faded, and
increased need for light
when reading
Senile miosis
Normal loss of light
restriction to the eye with
age
Decrease in resting
diameter of the pupil
9-24
AREDs
Diabetic retinopathy
Complication of
diabetes
Vessels in the retina
may hemorrhage
Normally clear vitreous
humor discolors
Detached retina can
occur
Presbyopia
Inability to focus clearly
on near objects as one
ages
9-25
Binocular Vision and Depth Perception
Binocular vision ~ coordinated eye movements
Strabismus ~ misaligned eyes
Common at birth, but diminishes during the first
week
Depth perception
A cerebral function based upon information sent by
the eye to the brain
9-26
Binocular Vision and Depth Perception
The Visual Cliff
Note the mother
attempting to coax the
infant into crossing the
apparent deep (cliff)
side
Infants are capable of
depth perception
Gibson & Walk’s
(1960) classic
experiment
9-27
Field of Vision
Refers to the entire extent of the environment
that can be seen without a change in fixation of
the eye
Normal lateral peripheral vision = 90 degrees from
straight ahead (180 degrees total)
Normal vertical peripheral vision = 47 degrees
above and 65 degrees below visual midline
9-28
Field of Vision
David’s 1987 experiment examining
peripheral vision processing during the
performance of a catching task
9-29
Aging and Depth Perception and Field of Vision
Both disease (AMD) and anatomical facial
changes may cause a loss of depth
perception/field of vision with age
Change in facial structure
Senile ptosis
Drooping of the eyelid
Loss of fat tissue around orbital socket
9-30
Eye Dominance
Refers to the ability of one eye to lead the other in
tasks involving visual tracking and visual fixation
Hole-in-card test
9-31
Eye Dominance
Unilateral dominance
Right-eyed and right-handed
Left-eyed and left-handed
Crossed-laterals dominance
Right-eyed and left-handed
Left-eyed and right handed
9-32
Tracking and Object Interception
Tracking an object allows the performer to gain
important information about the flight path of the
object
Smooth pursuit system
Matching of eye movement speed and speed of a
projectile
Saccadic eye-movement system
Corrects differences between projectile location
and eye fixation
9-33
Tracking and Object Interception
40-52
weeks
5-6 yr.
Can track a 180 degree arc
Can track objects in horizontal plane
8-9 yr.
Can track balls that travel in arc
9-34
Tracking and Object Interception
Bassin anticipation
time
Coincidenceanticipation
Process involving
object interception
9-35
Motor Development of
Children with Visual Impairments
9-36
Blindness
A definition of blindness is based upon distance
vision
Ranges from 20/200 (80% loss of vision) to total
blindness
Because visual curiosity elicits movement, the
unsighted child is not visually motivated to
explore the unseen world
9-37
Blindness
Head and trunk control
Curiosity encourages
lifting head and trunk
in sighted children
Unsighted child fusses
when in a prone
position – parent
places child on the
back which does not
help with head and
trunk control
Independent sitting
Occurs in sighted
children between 4
and 8 months
An unsighted child can
perform this task at
the same time if the
parents have prepared
the child
9-38
Blindness
Creeping
By 10 months a sighted
child can support
him/herself on hands
and knees to creep and
explore
An unsighted child has no
enticement to explore
Noise making toys help
the unsighted child to
creep
Independent walking
Both sighted and
unsighted children are
able to walk
independently at the
same time
However, this task is
usually delayed in
unsighted children
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Blindness
Prehension
Vision is extremely
important in
performing the task of
prehension
The unsighted child
exhibits a delay
Play
For the sighted child,
play is spontaneous
The unsighted child is
inactive and shows no
desire to experiment
with the environment
9-40
Bayley Scale Items
9-41
Nonvisual Senses
9-42
Proprioceptive System
The ability to be aware of location and
movements in space without visual references
A factor contributing to the development of body
awareness, spatial awareness, and directional
awareness
9-43
Proprioceptive System
Mechanoreceptors
Muscle spindles
Golgi tendon organs
Joint receptors
Vestibular apparatus
9-44
Proprioceptive System
Muscle spindles
Can gauge the amount of tension within the
muscle
Senses how the muscle is stretched
Golgi tendon organs
Monitors tension in the muscle
Joint receptors
“Limit detectors”
9-45
Classic Knee Jerk
9-46
Proprioceptive System
Vestibular apparatus
Located in the inner ear
Rotational motion
Semicircular canals (angular accelerometers)
Linear acceleration
Otolith organs (utricle and saccule)
9-47
9-48
Cutaneous System
Tactile sensitivity (skin)
Responses to tactile stimulation
Reflex response
Babinski reflex
Withdrawal response
Move away from unpleasant or painful object
Approach response
Response to kisses and hugs
9-49
Key Terms
9-50