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

Subliminal stimulation: messages that are received below the absolute threshold.

Rods of the eye:

• Neurons (called photoreceptors) that have been modified to detect black, white, and gray.

• They are also used in dim-light and peripheral vision

• Distributed throughout the back of the eye on the retina except for a little place called the fovea.

Cones of the eye:

• Photoreceptors that detect color and fine detail when the conditions are bright.

• Concentrated in the fovea (middle of the retina)

Rod and Cone demonstration

1. What can you tell about the ability of rods and cones to detect vision?

After Image activity (change to 105!!!)

 PROCEDURE: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 each trial?   

Blind Spot Activity1. 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. 

Answer: 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 the time?   

Homework, take notes on the following topics of chapter 4.

• Transduction (auditory cells of transduction? P. 96 and optic cells of transduction p.111

• Color –sight etc…and color blindness…• Trichromatic theory• Opponent-process theory• Weber’s law (actually page 130)• Vestibular and kinesthetic sense