Transcript Unit 2 - senses - Sir Wilfrid Laurier School Board

Senses & Sensory Relationships
– All of our senses respond to stimuli in the
environment/
– ________________________________________
– ________________________________________
________________________________________
– The role of sense receptors is to ______________
________________ and to provide the other parts
of the body with information about these stimuli.
Sense organs
(Fill out the following table)
Sense
Organ
Perception
Taste
Tongue
Salty, sweet,
spicy, bitter
1. The Eye
• The eye is the organ of sight.
• Our eyes enable us to appreciate:
– __________________
– __________________
– _____________________
– ____________________________________
• The eye is made up of a system of 4
_________ and 3 ___________ substances
Anatomy of the Eye
Membranes:
- 1 membrane covers the
front part of the eye .

__________________
- it is transparent
- under the cornea are:
1) _________: the coloured
ring of the eye
2) __________: the central
portion of this ring
(black dot)
Anatomy of the Eye
- the other 3 membranes line the
posterior (back) of the eye
They are all different:
1.
___________________________
_____________
- rigid, gives the eye its shape
2.
___________________________
- provides nourishment for the eye
3.
___________________________
- active nervous membrane =
receiver of stimuli
Anatomy of the Eye
Transparent Substances:
Found inside the eye
1. _________________
2. ________________________
- located between
the cornea and lens
- a liquid made up of water
and minerals
3. _________________________
- located between the lens
and the retina
- jelly like substance
What path does light take as it
travels through the eye?
1) Light must pass through a number of transparent media
before it reaches the nerve cells of the eye. Where are
these located?
 __________________
2) Label these different structures in the order that light
passes through:
vitreous humour, lens, retina, cornea, aqueous humour
1st _____________ 
2nd _____________ 
3rd ______________
4th ______________
5th ______________.
The Path Light Takes in the Eye
– Light passes through and is bent by the
cornea and then the lens. WHY?
____________________________________
____________________________________
– Images appear inverted(______________) on
the retina
• When looking at near-by objects = the lens curves
and thickens.
• When looking at far object = the lens flattens.
– The reflex that causes the lens to change
shape is called the _____________________
near-far sightedness
ugh
THE PROPERTY OF REFRACTION (BENDING IF LIGHT), we
are able to focus an image at the back of our eye, in the Retina.
Flattened lens
The image for which we see from the outside
environment is actually upside down on our retina.
The Brain flips it back so we can see right-side-up.
thickened lens
• Light rays enter the eye and focus on the retinal
nerve cells (neurons)
• These retinal nerve cells then change the light
waves that strike them into nerve impulses that
are carried along the optic nerve to the visual
center of the brain
• Optic nerve
– Nerve tissue formed by the axons of the
retinal cells
– Transmits nerve impulses form the retina to
the optical centre of the brain
• Examples of retinal nerve cells:
– Rods = detect light and dark
– Cones = detect colour
Visual pathway
Visual Sensory Mechanics
1. Stimuli
=
2. Receptor
=
3. Processor
=
4. Nerve Impulse =
5. Conductor
=
6. Analyzer
=
Light
Retina
Rods and Cones
Action Potential from Axons
Optic Nerve
Brain (Occipital Lobe)
• It is only when the center for vision in the
brain (in the occipital lobe) is stimulated that
a person has any visual sensation
• Therefore, it is not only the eyes alone that
allow us to “see” but also the brain.
Lenses
• Convex lenses
– Also called converging
– Cause light to
converge on a focal
point
– This is like the actual
lens inside your eye
• Concave lenses
– Also called diverging
lens
– Cause light to diverge
from a focal point
Eye Disorders
• Hyperopia (far-sighted):
• The image is focused behind the retina
• Close objects are blurred
– Requires CONVEX lenses
• Myopia (near-sighted):
• The image is focused in front of the retina
Long eyeball
Short eyeball
• Distant objects are blurred
Myopia
Hyperopia
– Requires CONCAVE lenses
• Presbyopia :
– loss of elasticity of the lens (usually in old age)
Common visual defects