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GENERAL PSYCHOLOGY-1
UNIT-2 (PART-2)
SHALINI A
ASSISSTANT PROFESSOR & HEAD
DEPARTMENT OF PSYCHOLOGY
RVS CAS

UNIT-2 ( PART-2)
SENSATION AND PERCEPTION
SENSATION: Meaning- Sensory
Thresholds- Sensory Adaptation- Basic
Sensation: Vision- Hearing-Touch and other
Skin senses- Smell and Taste- Kinaesthesia
and Vestibular sense
...


BASIC SENSATIONS
THE HEARING SENSE
If light works like waves, then do sound waves have
similar properties?
The properties of sound are indeed similar to those of
light, as both senses rely on waves
...


What is sound, and how does it travel through the
various parts of the ear?
Sound waves do have the same properties of light
waves though—wavelength, amplitude, and purity
...
Wavelengths are interpreted by the brain as the
frequency or pitch (high, medium, or low)
...
Amplitude is interpreted as volume, how soft or loud
a sound is
...
Finally, what would correspond to saturation or
purity in light is called timbre in sound, (the quality
of a sound) a richness in the tone of the sound
...
The everyday noises that
surround people do not allow them to hear many pure tones
...
Frequency or pitch :
shorter wavelengths = more waves per second = higher
frequencies
2
...
Timbre: increase in number of sounds results in greater
richness

a) A typical sound wave
...
If the waves
are close together in time (high frequency), the pitch will be
perceived as a high pitch
...


Decibels of various stimuli: A decibel is a unit of measure for
loudness
...


Just as a person’s vision is limited by the visible spectrum of
light, a person is also limited in the range of frequencies he or
she can hear
...
Human limits are between 20 and
20,000 Hz
...
) To hear
the higher and lower frequencies of a piece of music on a CD,
for example, a person would need to increase the amplitude or
volume
...
)

The Structure of the Ear
THE OUTER EAR

The pinna is the visible, external part of the ear that funneling
(Moving to a focal point) the sound waves from the outside
into the structure of the ear
...
When sound
waves hit the eardrum, they cause three tiny bones in the
middle ear to vibrate
...
The vibration of these three bones amplifies the
vibrations from the eardrum
...


Pinna

This drawing shows the entire ear, beginning with the
outer ear (pinna, ear canal, and eardrum)
...


Ear Canal

Vestibular organ
(semicircular canals)

Auditory Nerve

Eardrum
Cochlea

Hammer

Anvil

Oval Window

Stirrup

Eardrum

Middle Ear

The middle ear
...
The stirrup rests on the oval
window, which transmits its vibration to the fluid in the
inner ear
...

a
...
When the oval window vibrates, it
causes the fluid in the cochlea to vibrate
...

b
...
When the basilar membrane vibrates, it vibrates the
organ of Corti, causing it to brush against a membrane above
it
...


Organ of Corti

Fluid in Cochlea
Basilar Membrane
The inner ear
...
A thin
membrane suspended in this fluid is called the basilar
membrane, which contains the organ of Corti, the structure
composed of the hairlike cells that send signals to the auditory
cortex of the brain by way of the auditory nerve
...

Notice the axons (small green lines) leaving the hair
cells to form the auditory nerve
...
The
louder the sound in the outside world, the stronger the
vibrations that stimulate more of those hair cells—which the
brain interprets as loudness
...
There are three
primary theories about how the brain receives information
about pitch
...

In this theory, the pitch a person hears depends on where the hair
cells that are stimulated are located on the organ of Corti
...


Frequency theory, developed by Ernest Rutherford in 1886,
states that pitch is related to how fast the basilar membrane
vibrates
...
(In this theory,
all of the auditory neurons would be firing at the same time
...
For place-theory research to be
accurate, the basilar membrane has to vibrate unevenly—
which it does when the frequency of the sound is above 1000
Hz
...
This only works up to 1000 Hz,
because neurons don’t appear to fire at exactly the same time
and rate when frequencies are faster than 1000 times per
second
...
Is there another
explanation? Yes, and it is a third theory, developed by Ernest
Wever and Charles Bray, called the volley principle theory,
which appears to account for pitches from about 400 Hz up to
about 4000
...
If a person hears
a tone of about 3000 Hz, it means that three groups of neurons
have taken turns sending the message to the brain—the first
group for the first 1000 Hz, the second group for the next 1000
Hz, and so on
...
)

TYPES OF HEARING IMPAIRMENT
Hearing impairment is the term used to refer to difficulties in
hearing
...

Why are some people unable to hear, and how can their hearing
be improved?
1
...
The cause
might be a damaged eardrum or damage to the bones of the
middle ear (usually from an infection)
...


2
...
Normal aging causes loss of hair cells in the cochlea,
and exposure to loud noises can damage hair cells
...
( isn’t caused by an external sound, and other
people usually can’t hear it)

Because the damage is to the nerves or the brain, nerve
hearing impairment cannot be helped with ordinary
hearing aids, which are basically sound amplifiers
...


Cochlear implant: This device sends signals from a microphone
worn behind the ear to a sound processor worn on the belt or
in a pocket, which then translates those signals into electrical
stimuli that are sent to a series of electrodes implanted directly
into the cochlea, allowing transduction to take place and
stimulating the auditory nerve
...


microphone
headpiece
cochlea

implant

Speech Processor

Auditory nerve

Electrode array

In a cochlear implant, a microphone implanted just behind the
ear picks up sound from the surrounding environment
...
The implant itself is a transmitter and receiver,
converting the signals from the speech processor into
electrical impulses that are collected by the electrode array in
the cochlea and then sent to the brain
...
Hearing spoken language during the early
years of a child’s life helps in the development of the
child’s own speech
...

Have you ever noticed that when your nose is all stopped
up, your sense of taste is affected, too? That’s because the
sense of taste is really a combination of taste and smell
...

Most taste buds are located on the tongue, but there are a few on the
roof of the mouth, the cheeks, and under the tongue as well
...
The latter are called “supertasters” and
need far less seasoning in their food than those with fewer taste
buds
...


Taste is often called a chemical sense because it works with
the molecules of foods people eat
...

What happens to the taste buds when burn tongue?
Do they repair themselves?
when we burned our tongue, we can’t taste much for a while, but
the taste comes back
...

And when the tongue is burned, the damaged cells no longer
work
...


The right side of this drawing shows the
nerves in the tongue’s deep tissue
...


Microphotograph of the surface of the tongue, showing two different sizes of
papillae
...


THE FIVE BASIC TASTES
In 1916 a German psychologist named Hans Henning
proposed that there are four primary tastes: sweet, sour,
salty, and bitter
...
Lindemann proposed that this fifth taste be called
umami, a Japanese word first coined in 1908 by Dr
...

The five taste sensations work together, along with the sense of
smell and the texture, and “heat” of foods, to produce
thousands of taste sensations

THE SENSE OF SCENTS (OLFACTION) (olfaction -olfactory
sense: the sensation of smell
...

The ability to smell odours is called olfaction, or the olfactory
sense
...
The part of
the olfactory system (that turns odors into signals the brain can
understand) is located at the top of the nasal passages
...


Olfactory bulb
Cilia of olfactory receptor cell

Olfactory epithelium

This drawing shows the nerve fibers inside the
nasal cavity that carry information about smell
directly to the olfactory bulb just under the
frontal lobe of the brain (shown in green)
...
The olfactory bulb is on
top
...
These
are the receptors for the sense of smell
...

Olfactory receptors also have to be replaced as they naturally
die off, about every 5 to 8 weeks
...

Vision, hearing, taste, and touch all pass through the thalamus
and then on to the area of the cortex that processes that
particular sensory information
...


THE OLFACTORY BULBS

The olfactory bulbs are located right on top of the sinus
cavity on each side of the brain directly beneath the frontal
lobes
...
The olfactory information is
then sent from the olfactory bulbs to higher cortical areas,
including the primary olfactory cortex, the orbitofrontal
cortex, and the amygdala

Somesthetic Senses: What the Body Knows
The first part of that word, soma, means “body,”
...
somesthetic
senses is refers to the body senses consisting of the skin
senses, the kinesthetic sense, and the vestibular senses
...
skin senses: the sensations of touch, pressure, temperature,
and pain
...
kinesthetic sense: (proprioception) sense of the location of
body parts
...

3
...
(body position and movement of the head)

PERCEPTION OF TOUCH, PRESSURE, AND TEMPERATURE

What allows people to experience the sense of touch, pain,
motion, and balance?
What organ of the body is about 20 square feet in size?
The answer is the skin
...
Its purposes include
more than simply keeping bodily fluids in and germs out; skin
also receives and transmits information from the outside world
to the central nervous system (specifically, to the
somatosensory cortex)
...


TYPES OF SENSORY RECEPTORS IN THE SKIN

There are about half a dozen different receptors in the layers of
the skin
...
For example, the Pacinian corpuscles are just
beneath the skin and respond to changes in pressure
...
These nerve
endings are sensitive to both pain and touch
...


Skin Surface

Hair
Sweat gland

Skin
layers

Pressure sensitive
nerves
Blood
vessels

Subcutaneous
Pain-sensitive and touch- fat
sensitive free nerve endings

The skin is composed of several types of cells that process pain, pressure,
and temperature
...


How exactly does pain work? Why is it that sometimes we feel pain deep
inside? Are there pain receptors there, too?
Yes, there are pain nerve fibers in the internal organs as well as receptors
for pressure
...
There are receptors that detect
pain (and pressure) in the organs, a type of pain called visceral pain
...
We experience it when our internal organs and
tissues are damaged or injured
...
Somatic pain occurs when
pain receptors in tissues (including the skin, muscles, skeleton, joints, and
connective tissues) are activated
...


Somatic pain is the body’s warning system that something is
being, or is about to be, damaged and tends to be sharp and
fast
...
This somatic
pain acts as a kind of reminder system, keeping people from
further injury by reminding them that the body has already
been damaged
...
But later the bruised tissue simply
aches, letting you know to take it easy on that thumb
...
There are people who are born without the
ability to feel pain, rare conditions called congenital analgesia
and congenital insensitivity to pain with anhidrosis (CIPA)
...
They fear nothing—which can be
a horrifying trial for the parents and teachers of such a child
...

A condition called phantom limb pain occurs when a person who
has had an arm or leg removed sometimes “feels” pain in the
missing limb
...
In this theory, the pain signals must pass
through a “gate” located in the spinal cord
...
The
gate is not a physical structure but instead represents the
relative balance in neural activity of cells in the spinal cord
that receive information from the body and then send
information to the brain
...
Substance P released into
the spinal cord activates other neurons that send their messages
through spinal gates (opened by the pain signal)
...
The brain then interprets
the pain information and sends signals that either open the
spinal gates farther, causing a greater experience of pain, or
close them, dampening the pain
...
Anxiety, fear, and helplessness
intensify pain, whereas laughter, distraction, and a sense of
control can diminish it
...
)

THE KINESTHETIC SENSE

Special receptors located in the muscles, tendons, and
joints are part of the body’s sense of movement and
position in space—the movement and location of the
arms, legs, and so forth in relation to one another
...
When
you close your eyes and raise your hand above your
head, you know where your hand is because these
special receptors, called proprioceptors, tell you
about joint movement or the muscles stretching or
contracting
...
Also called kinaesthesia; kinesthetic sense; movement
sense
...
These are found in
muscles, tendons, and joints
...


What is the vestibular system and what does it do?
The vestibular system is a sensory system that is
responsible for providing our brain with information
about motion, head position, and spatial orientation; it
also is involved with motor functions that allow us to
keep our balance, stabilize our head and body during
movement, and maintain posture
...


Vestibular sensations begin in the inner ear in the
vestibular labyrinth, a series of interconnected
chambers that are continuous with the cochlea
...
These consist of
three tubes, positioned approximately at right angles to
one another, that are each situated in a plane in which
the head can rotate
...
These movements of the head around an
axis are referred to as rotational acceleration, and can
be contrasted with linear acceleration, which involves
movement forward or backward
...
These receptors send
vestibular information via the vestibulocochlear nerve
to the cerebellum and to nuclei in the brainstem called
the vestibular nuclei
...


A) The otolith organs are tiny sacs found just above the cochlea
...
The head moves and the crystals cause the fluid to
vibrate, setting off some tiny hair like receptors on the inner surface
of the sac, telling the person that he or she is moving forward,
backward, sideways, or up and down
...
Having three tubes allows one to be located in each of the
three planes of motion
...
When you spin around and then stop, the fluid in the
horizontal canal is still rotating and will make you feel dizzy
because your body is telling you that you are still moving, but your
eyes are telling you that you have stopped
...
Normally, the vestibular sense coordinates
with the other senses
...
This explanation of
motion sickness is known as sensory conflict theory

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