LECTURE 19: Sensation (Chapter 15)
•Vision’s advantage is distance because it helps us tell how far an object is, deal with predators
and improves our ability to work with things.
•Those with good visual perceptions tend to survive longer.
•Audition helps you hear things from far away, but with vision we get a precise idea of what we
see. Sounds can be unclear as the frequencies don’t come clear or sometimes there is a
•Vision is more clear and correct from distance.
•We see only a small part of this called the visible spectrum. It ranges from light with
wavelengths of between 380 nanometers (violet) up to 760 nanometers (red).
•Iris - The coloured part of your eye … it is actually a
muscle that controls the size of the pupil. It can dilate
or open the pupil.
•Pupil - The black part in the middle of the eye …
simply is the opening that allows light into the
•Sclera - The white part of the eye … a tough
membrane that serves as protection for the eye
itself. Outside walls of the eye.
•Cornea - The fluid filled outer coating of the eye … provides moisture and nutrients to the
•Retina – The outside world is being projected onto the retina. If the eye is properly shaped, a
nicely focused image lands on the inner coating of the back of the eye. This inner coating is
the retina, and it is the part that transmits the light signal (focused or not) into a neural signal.
•Lens - sits behind the pupil and focuses the incoming light onto the retina. This lens is
flexible and slight alterations in it can alter the focus of it, a process called accommodation (as
an example, squint- you are binding the lens behind your eye which allows sharpness). As
people age, the lens begins to lose its softness and you are unable to squint and adjust your
reading lenses and that’s when they need the reading glasses. Lens helps you see close up