Transcript Sensation - Cloudfront.net

Sensation
How the brain recognizes
information from our senses
Characteristics of
ALL senses
 Transduction: the process in which a sense
organ changes, or transforms, physical
energy into electrical signals that become
neural impulses, which can then be sent to
the brain for processing.
 Adaptation: the decreasing response of the
sense organs, the more they are exposed to
a continuous level of stimulation.
Sensations vs. Perceptions
 Sensations are relatively meaningless bits of
information that result when the brain
processes electrical signals that come from
the sense organs.
 Perceptions are meaningful sensory
experiences that result after the brain
combines hundreds of sensations.
Eye; Vision Structure and Function
 Image reversed: All
images seen by the
eye are reflected
upside down and
somehow turned right
side up by the brain.
Eye: Vision Structure and Function
 Light waves: The eye
light waves in the
direction you are
looking to reflect all
things in your field of
vision. The beams are
brought into focus by
the cornea and the
lens… much like a
camera focus.
Eye: Vision Structure and Function
 Cornea: Rounded,
transparent
covering over the
front of the eye.
 Light passes
through cornea; its
curved surface
bends, or focuses,
the light waves into
narrower beams.
Eye: Vision Structure and Function
 Pupil: round opening at
the front of your eye
that allows light waves
to pass into the eye’s
interior.
 The pupil grows larger
or smaller because of
a muscle called the
iris.
Eye: Vision Structure and Function
 Iris: circular muscle that
surrounds the pupil and
controls the amount of
light entering the eye.
 In dim light the iris
relaxes, allowing more
light to enter (pupil
dilates).
 In bright light the iris
constricts, allowing less
light to enter.
 Contains pigment that
gives your eye its color.
Eye: Vision Structure and Function
 Lens: transparent, oval
structure whose
curved surface bends
and focuses light
waves into an even
narrower beam.
 Lens is attached to
muscles that adjust the
curve of the lens which
adjusts the focusing.
Eye: Vision Structure and Function
 Retina: located at the
very back of the
eyeball
 Thin film that contains
cells that are extremely
sensitive to light.
 These light sensitive
cells, called
photoreceptors, begin
the process to
transduction by
absorbing light waves.
Ear: Audition
 Sound waves are the stimuli for hearing
(audition), resemble ripples of different
sizes.
 Amplitude: distance from bottom to top of
sound wave. Measures loudness; large
amp = loud, small amp = quiet
 Frequency: speed in which sound waves
occur. Measures pitch; fast = high pitch,
slow = low pitch.
Measuring Sound Waves
Outer Ear
 Three Parts: external
ear, auditory canal,
and tympanic
membrane.
Outer Ear
 The external ear is an
oval shaped structure
that protrudes from the
side of the head.
 The function of the
external ear is to pick
up sound waves and
send them down a
long, narrow tunnel
called the auditory
canal.
Outer Ear
 Auditory Canal: long
tube that funnels
sound waves down its
length so that the
waves strike a thin,
taut membrane
(eardrum) or tympanic
membrane.
Outer Ear
 Tympanic Membrane: a
taut, thin structure
commonly known as the
eardrum.
 Sound waves strike the
membrane and cause it
to vibrate.
 It then passes the
vibrations on to the first
of three small bones it is
attached to.
Middle Ear
 Bony cavity that is sealed at each end by
membranes. The two membranes that seal
the area is connected by three small bones
which make up the middle ear.
 Collectively, the three bones are known as the
ossicles.
 Because of their shape they are known as the
hammer, anvil, and stirrup.
 Together the ossicles serve as levers to
greatly amplify sound waves and pass them
on to the inner ear.
Inner Ear
 Cochlea: has a bony coiled exterior that resembles
a snail’s shell.
 Contains receptors for hearing and its function is
transduction (transforming) vibrations into nerve
impulses that are sent to the brain for processing
into auditory information.
 The cochlea processes this information by using
hair cells in the bottom called the basilar
membrane.
 The auditory nerve is a band of fibers that carry
nerve impulses (electrical signals) to auditory
cortex in the brain for processing.
Vestibular System
 Located above the cochlea in the inner ear,
includes three semicircular canals,
resembling bony arches, which are set at
different angles.
 Each canal is filled with fluid that moves in
response to movements in your head.
 The functions of this system include sensing
the position of the head, keeping the head
upright, and maintaining balance.
Chemical Senses: Taste
 Taste is called a chemical sense because
the stimuli are various chemicals.
 On the surface of the tongue are receptors,
called taste buds, for four basic tastes…
sweet, salty, sour, and bitter.
 The function of the taste buds is to perform
transduction, which is transforming chemical
reactions into nerve impulses.
Taste Buds
Chemical Senses: Taste
 Taste buds are physically shaped like tiny
onions and are our only receptors for taste.
 Chemicals dissolved in the saliva activate
the taste buds, which produce nerve
impulses that eventually reach areas in the
brain’s parietal lobe.
 Flavor: combined sensations of taste and
smell.
Chemical Senses: Smell
 Smell (Olfaction) is called a chemical sense
because its stimuli are various chemicals
that are carried by the air.
 The upper part of the nose has a small area
that contains receptor cells for olfaction…
their function is transduction.
 These olfactory cells dissolves molecules in
the air with mucus which triggers the nerve
impulses to the brain.
Touch
 The sense of touch includes pressure,
temperature, and pain.
 Beneath the outer layer of skin are a halfdozen miniature sensors that are receptors.
 The function of these receptors is to change
mechanical pressure or changes in
temperature into nerve impulses to the
brain.
Receptors in the Skin
 Skin: The body’s largest
organ.
 The outermost layer is a
thin film of dead cells
containing no receptors.
 The first receptors are
below the dead skin.
 Middle and fatty layers of
skin also have a variety
of receptors.
Receptors in the Skin
 Hair Receptors: hairs
respond with fire or
burst of activity when
bent, however, when
bent for a long time
they cease to fire.
 This is sensory
adaption.
Receptors in the Skin
 Free Nerve Endings:
located near the
bottom layer of skin
 These receptors are
what feel things such
as pain and
temperature.
Receptors in the Skin
 Pacinian Corpuscle:
Located in the fatty layer
of skin… largest touch
sensor
 Has distinctive layers
like an onion
 Highly sensitive to touch,
but adapts quickly.
 Only receptor to respond
to vibration.
Pain
 Pain is an unpleasant sensory and emotional
experience that may result from tissue
damage, one’s thoughts or beliefs, or
environmental stressors.
 How it works: pain receptors in the body
send nerve impulses to the somatosensory
and limbic areas of the brain, where impulses
are changes into pain sensations.
 Pain helps us survive; it is our warning
system.
Gate Control Theory of Pain
 Theory that states that
a human can create an
imaginary gate the
blocks pain messages
to the brain by shifting
attention.
 Examples:
Concentrate on other
tasks, rubbing area,
sleeping, exercise
(releasing endorphins).