Lecture of 9-11-06
What did we do on Friday?
•Got the AP-focus book from the media (the Approaches book
should be in your possession by the 22nd or so. Get it in the Media
Center for $40, borrow from an old student, get one online, or go
to the IB office for help…)
•Heard a sound that old people can’t hear
•Saw a demonstration of perspective (children’s book –Zoom)
•Drew both an eye and an ear and labeled the parts.
The following slides have
background information needed
to understand sensation:
The cells of the nervous system
are called neurons.
Sensation is a process where the body
takes physical energy and converts it to
a neuronal signal.
Absolute threshold is the weakest
level of a stimulus that can be
detected ½ of the time
messages that are received below
the absolute threshold.
Rods of the eye:
• Neurons (called photoreceptors) that have
been modified to detect black, white, and
• They are also used in dim-light and
• Distributed throughout the back of the eye
on the retina except for a little place called
Cones of the eye:
• Photoreceptors that detect color and fine
detail when the conditions are bright.
• Concentrated in the fovea (middle of the
Rod and Cone demonstration
1. What can you tell about the ability
of rods and cones to detect vision?
After Image activity (change to
1. Place a small square of solid blue paper or
cardboard on a sheet of white paper and
put it under the light.
2. Stare intently at it for 60 seconds.
3. Shift your gaze and to a plain white paper.
4. Repeat the process with a yellow square.
ANSWER: What color was the afterimage of
Blind Spot Activity
1. On a sheet of white paper, mark a small heavy black “X”, and
a heavy black dot 8 cm apart.
2. Cover your left eye, and hold the paper at arm’s length with
the dot at the left and the “X” at the right.
3. Stare hard at the dot while you slowly move the paper toward
you. Note that the “X” is visible at first, disappears completely,
and then reappears.
A) How far away is the paper when you stop seeing the “X”?
B) Move the paper up and down, and in a circle… what is the
shape of your blind spot?
C) Does your blind spot have a regular or irregular shape?
D) Explain why you have a blind spot in each eye.
E) Why don’t you have an empty space in your field of vision all of
Homework, take notes on the
following topics of chapter 4.
• Transduction (auditory cells of
transduction? P. 96 and optic cells of
• Color –sight etc…and color blindness…
• Trichromatic theory
• Opponent-process theory
• Weber’s law (actually page 130)
• Vestibular and kinesthetic sense