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Lecture

PSY313H5 Lecture Notes - Visual Acuity, Vitreous Body, Aqueous Humour


Department
Psychology
Course Code
PSY313H5
Professor
Giampaolo Moraglia

Page:
of 19
Thursday January 24, 2013
LECTURE 3: SENSORY AGING
Today:
Many topics not mentioned in textbooks
Sensory process change over time plays a fundamental role in our later years and decades
Any perceptional experience always arises from an encounter from sources of
environmental stimulation
Specialized sensory systems occur due to stimulus (acoustic energy enters our ears
stimulating receptors)
-Mechanical pressure, for touch…
-In general most of us will experience some loss of sensitivity as we age
No other age related loss is as universal as sensory loss
GENERAL ASPECTS OF SENSORY FUNCTIONING
Each sensory system responds to specific forms of energy (and to the
information carried by this energy) present in the environment
Energy levels are picked up by specialized receptors and recoded into
nerve impulses (‘sensory transduction’)
These nerve impulses are carried by sensory nerves to the brain….
Where they are analyzed and interpreted within specialized sensory
areas
There are many obvious differences in sensory differences
At the fundamental level all sensory systems share basic features
Sensitive to some sort of energy in the environment
Energy has to be picked up by special receptor cells located in sensory organs and
converted into electrical nerve signals (SENSORY TRANSDUCTION)
These nerve signals are carried by sensory nerves to specialize in the centers of
the brain where the info they contain will be analyzed and interpreted
AGE RELATED CHANGES OCCUR AT AL LEVELS OF A SENSORY SYSTEM
Sensory organs and receptors
Sensory nerves
Sensory areas within brain
-Loses that come with aging may occur at different levels in the sensory systems
-Sensory loss may be causes by:
1. Deteriorationsomething goes wrong in our sensory organs
2. Degeneration in our nerve fibers that connect our sensory nerves, which connect
to the brain
3. Directly in the brain itself
-Sensory decline may also be caused or sped up by disease, abuse, or disabuse
2
VISION & HEARING ARE THE ‘DOMINANT’ SENSES IN HUMANS
Significant impairments in the functioning of these sensory systems
seriously impair people’s ability to negotiate the environment
Any sensory loss interferes with the world
-Isolation of a person with loss to any dominate senses
-Severe hearing loss may find it tiring to keep up, and may result in social
isolation and may lead to mental health
-Disturbing effect in college students
-EXPERIMENT: Students had to deal with sensory loss that many older adults have
to live with, where they had plugs inserted into their ears and wear glasses and
asked to shop at the super market)
Disorientation; fumbling
Significant problems in the environment
BASIC FEATURES OF THE HUMAN EYE
Size of a ping pong ball and nearly spherical
3 layers:
1. Sclerotic coat: Withstands atmospheric pressure and becomes transparent
towards the front when it becomes the cornea
2. Choroid carries nutrients, become visible in the central portion and is called
the aqueous humor and the iris
At the centre of the iris is the hole, which is the pupil, which will constrict or
dilate with the amount of light in the environment
Dark pupil will open up to allow as much light in as possible
Changes with emotional arousal of an individual (size of the pupil
because pupil responds to emotional arousal)
3. Retina contains several millions of cells and receptors which is specialized to
capture particles of light, lead to generation of nerve signals
3
2chambers:
1. Aqueous humor chamber: filled with fluid
2. Largest portion of the eye is the vitreous humor, which contains a jelly like
substance
Lens can change curvature (refractor/bending)
-If the eye is looking at a far away object (5-6metres away or beyond) lens is
perfectly flat
-Lens will refract or bend light rays in order to focus (retina)
-Shift gaze to something closer, if the lens remained flat the image will be
unfocused in the retina
-Changing the refractory of the lens, muscles will contract increasing the
curvature of the lens, and the ability of lens to bend will increase in the amount
sufficient for the image to be projected in the retina, so the image will be sharp
but only to a point
Near point: can still see an object clearly, but if continues lens can no longer
bend to compensate and image will be blurred
SOME ‘NORMAL’ AGE RELATED CHANGES WITHIN THE EYE
Vitreous humor loses some transparency
Senile miosis (reduction in maximum size attainable by the pupil)
Pupil size changes more slowly
The lens loses some transparency, thickens, hardens (hence losing
flexibility), and turns yellowish
Vitreous humor chambers: become more opaque, loses some of its
transparency and limits amount of light allowed in
-Not continuously regenerated: waste product of the metabolicity of the eye, and
settle at the bottom of the eye
-Shower: out of nowhere you see a shower of tiny sparks, which is a sign that
your retina is at risk of being detached (report immediately)
Pupil: (small opening at the centre of the iris) the iris gets smaller with age further
limiting the amount of light that can enter the eye, and leads to the decreasing size
of a pupil; amount of light that reaches the retina may be reduced by 60-65% by the
age of 60
As we get older the pupil responds more slowly, its widening and
constricting abilities to accommodate changes in the ambient illumination
(sudden) due to the weakening of the muscles that control the pupil
Lens: when we are born, the lens is quite tiny and grows throughout one’s life and
adds layers over time and gets thicker
The older cells over time lose most of the water they come up with and
shrivel and harden
Due to this the lens becomes less transparent reducing the amount of light
allowed in which leads to pupil being unable to open up
Around 35, the lens begins to turn yellow. Discriminate to green, blue, and
violet ray in the short end of the spectrum