Download Psychology 8.2 - Packet 8-2

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For use with textbook pages 214-222
Key Terms
pupil the opening in the iris that regulates the amount of light entering the eye (page 215)
lens a flexible, elastic, transparent structure in the eye that changes its shape to focus light on
the retina (page 215)
retina the innermost coating of the back of the eye, containing the light-sensitive receptor
cells (page 215)
optic nerve the nerve that carries impulses from the retina to the brain (page 215)
binocular fusion the process of combining the images received from the two eyes into a single, fused image (page 216)
retinal disparity the differences between the images stimulating each eye (page 216)
auditory nerve the nerve that carries impulses from the inner ear to the brain, resulting in the
sensation of sound (page 218)
vestibular system three semicircular canals that provide the sense of balance located in the
inner ear and connected to the brain by a nerve (page 220)
olfactory nerve the nerve that carries smell impulses from the nose to the brain (page 220)
kinesthesis the sense of movement and body position (page 222)
Drawing From Experience
Have you ever tried to do something with one eye closed? Was the activity
more difficult to do this way? Have you ever felt dizzy after riding on a roller
coaster or a boat?
In the last section, you learned about the nature of sensations and their
thresholds. This section discusses how your body receives and processes sensations from your environment.
Organizing Your Thoughts
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Use the diagram below to help you take notes as you read the summaries
that follow. Think about the path that light takes from the time it hits your eye
until it becomes vision. Trace the steps in the process in the flowchart below.
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Read to Learn
Introduction (page 214)
You probably think that you have just five senses: vision, hearing, taste,
smell, and touch. Actually, you have more. The skin has several senses. Plus,
you have two "internal" senses: vestibular and kinesthetic. Each sense organ
receives some sort of external stimulus, such as light, sound waves, or pressure.
It then changes the sensation into a chemical-electrical message transmitted
by the nervous system and interpreted by the brain.
6.
What are the sense organs for the five familiar senses?
Vision (page 215)
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The vision process begins when light enters the eye through the pupil and
reaches the lens. This is a flexible structure that changes its shape to focus light
on the retina. The retina is a coating at the back of the eye. It contains two types
of light-sensitive cells: rods and cones. These cells change light into impulses
that the neurons carry over the optic nerve to the brain.
Cones require more light than rods before they begin to respond, so cones
work best in daylight. Since rods can work in much lower light, they are the
basis for night vision. There are many more rods than cones, but only cones are
sensitive to color.
The colors we see are actually different wavelengths of light. We see color
only after light waves hit objects and bounce back to us. For example, a pea
looks green because green light bounces off of it and all other colors do not. We
can sense differences in texture and solidity of objects by the speed at which
the waves bounce back.
When the cones are not working well, the person can not see color very well.
This condition is called color deficiency. For example, some people can not tell
the difference between red and green. A few can't tell yellow from blue. A very few
can't see any colors at all. They see the world in blacks, whites, and shades of gray.
Because we have two eyes, our visual system receives two images. But
instead of seeing double, we see a combination of the two images. This is called
binocular fusion. Each eye projects a slightly different image on the retina. This
difference is called retinal disparity. For example, bring an object such as an
eraser close to your eyes. Without moving it, look at the eraser first with one eye
and then with the other. You will see a difference in the two images because of
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the different viewpoint each eye has. When you open both eyes, you will see no
difference. You will see one eraser.
Retinal disparity is important to your sense of depth. Your brain knows
that a large difference between the images each eye brings in (retinal disparity)
means the object is near. A small difference means the object is far away.
7.
Bring a small object very close to your face. Look at it with one eye and then the other.
Notice the differences in the two images. Then do the same with a distant object. Which
object creates the greatest difference in what each eye sees?
Hearing (page 218)
Hearing depends on sound waves. These are vibrations of the air. Sound
waves from the air pass through several bones and fluids until they reach the
inner ear. The inner ear contains tiny hairs that move back and forth, like a
field of wheat in the wind. These hairs change the sound vibrations into signals
that the neurons carry through the auditory nerve to the brain.
The amplitude, or height, of sound waves determines the loudness. The
higher the amplitude, the louder the sound. Loudness is measured in decibels.
The sound's pitch depends on the wave's frequency, or rate of vibration. Low
frequencies produce deep bass sounds. High frequencies produce squeaks. You
can hear more than one pitch at a time. For example, if you strike two piano
keys at the same time, you can pick out two different pitches.
Your ears work together to tell you where the sound is coming from. For
example, a noise on your right will reach your right ear first and then your left.
It is also slightly louder in your right ear because it is closer to it. These differences tell you the direction of the sound.
Your outer ear directs sound waves down a short tube called the auditory
canal. The vibration (sound wave) causes air in the auditory canal to vibrate,
which in turn causes the eardrum to vibrate. The middle ear is filled with air
and contains three bones: the hammer, anvil, and stirrup. These bones link to
the eardrum on one end and the cochlea at the other. When the eardrum
vibrates, the three bones in the middle ear vibrate and push against the
cochlea.
The cochlea is the inner ear. It is a tube that contains fluids and neurons.
The pressure against the cochlea makes the liquid in it move. Tiny hairs inside
the cochlea pick up the motion. The hairs are attached to sensory cells. These
cells turn the sound vibrations into impulses that the neurons in the auditory
nerve carry to the brain.
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When you hear sounds from a bass guitar, are you hearing waves with high frequency or
low frequency?
Balance (page 22O)
Your body's sense of balance comes from the vestibular system inside
your inner ear. It has three semicircular canals filled with fluid. When you turn
your head, this fluid moves, which bends hair cells in the fluid. The stimuli that
your vestibular sense responds to are movements such as spinning, falling, and
tilting your head. Too much stimulation of this sense can cause dizziness and
"motion sickness." Without your sense of balance, you would be unable to walk
without falling.
9.
Give an example of an activity that might overstimulate your vestibular system.
Smell and Taste (page 22O)
Smell and taste are chemical senses. Their sense organs respond to chemical molecules rather than to light energy or sound waves. To smell something,
the right molecules must hit the smell receivers in your nose. These molecules
enter your nose in vapors, which reach smell receivers in the nasal passages.
These receivers send messages about smells through the olfactory nerve to the
brain. To taste something, molecules must stimulate the taste buds on your
tongue. The taste buds relay information about taste as well as texture and
temperature of the substance to the brain.
Four sensory experiences make up taste: sour, salty, bitter, and sweet. The
combination of taste, smell, and touch sensations create flavor. Much of what
you taste is actually produced by your sense of smell. For example, when your
nose is blocked by a cold, your food probably tastes bland.
Sensations of warmth, cold, and pressure also affect taste. Try drinking hot
soda to see how temperature affects taste. Now think about the differences in
texture between pudding and a crunchy chocolate bar. These textures influence
taste as well.
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10. Is the sense of smell better in dogs or humans? Give an example.
The Skin Senses (page 221)
Your skin provides at least four kinds of information to your brain: pressure, warmth, cold, and pain. Some spots on your skin are more sensitive to
pressure than others because they contain more receivers. For example, your
fingertips contain many receivers and are highly sensitive to pressure. Your
calves have few receivers. Some skin receivers are sensitive to hot or cold. To
create a hot or cold sensation, the temperature of the stimulus must be greater
or less than the skin's temperature.
Stimuli such as scratches, punctures, and very high heat can produce pain.
Pain is your body's emergency system. It warns you of possible damage to your
body from such stimuli. Pain motivates you to stop the harmful activities and
take care of injuries. There are two kinds of pain. Pain can be sharp and in a
specific spot, or pain can be a dull ache over larger portions of your body.
According to the gate control theory of pain, we can reduce some pain by
shifting our attention away from it, or we can send other signals to compete
with the pain signals. Only so many impulses can get through the bottleneck,
or gate. So by increasing nonpain impulses (like rubbing your stubbed toe), you
decrease the pain impulses that get through.
11. Use the gate control theory of pain to explain why an injured athlete may be able to continue playing in the game.
The Body Senses (page 222)
Kinesthesis is the sense of movement and body position. It works with the
vestibular system to control posture and balance. The receivers for kinesthesis
are located near the muscles, tendons, and joints. These receivers send messages to the brain when movement occurs.
Without kinesthetic sensations, your movements would be uncoordinated.
You would not know what your hand was doing if it went behind your back.
You could not walk without looking at your feet. Complex activities like surgery
would be impossible.
12. Give an example of a kinesthetic sensation needed to play tennis.
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