Download Sensory Mechanisms

Sensory Mechanisms
Energy Senses--Vision
• Visual Sense—turns light energy into a
neural message (transduction)
– Light is reflected off objects and gathered by
the eye
• Your red shirt simply reflects red wavelengths
– The color we perceive depends on intensity
and light wavelength.
Energy Senses--Vision
• Light is reflected first through the
CORNEA—a protective covering
• Next, light goes through the PUPIL—open
space.
• This is controlled by the IRIS—colored
part of the eye and the hardest working
muscle in the body. The IRIS either
expands or contracts letting less or more
light in. This is called accommodation.
Energy Senses--Vision
• Light is focused by the LENS
Try this—work those LENS muscles!
• Light is inverted and projected onto the
RETINA--a screen on the back of your eye
with specialized neurons activated by
different wavelengths.
• RETINA contains RODS and CONES
Energy Senses--Vision
• Rods—black and white
• Cones—color and bright
• Fovea—concentration of cones in the
retina
• TEST IT OUT—marker test!
• If enough rods or cones are activated,
then a bipolar cell fires, then a ganglion
cell fires next which connects to the optic
nerve.
Energy Senses--Vision
• The axons of the ganglion cells make up the
optic nerve which sends messages to the LGN
(lateral geniculate nucleus) of the Thalamus.
• The spot where the optic nerve leaves the
eyeball is called the blind spot--do the blind spot
test in the book!
• The optic nerve is divided into two parts and the
spot where the nerves cross is called the optic
chiasm.
Thalamus--LGN
Thalamus--LGN
Energy Senses--Vision
• Feature Detectors—Hubel and Weisel
• Nobel Prize for their work
• Groups of neurons in the visual cortex that
respond to vertical lines, curves, motion,
etc..
Energy Senses--Vision
• 2 Theories of Color Vision
– Trichromatic Theory—blue, red, and green
• Combine to form spectrum
• People who are color blind are missing one
or more color receptors
• Some animals may be dichromatic or
monochromatic—dogs are dichromatic and
are missing green!
Energy Senses--Vision
• Opponent Process Theory—
– Sensory receptors come in pairs, which
explains the after image effect
• Red/green
• Yellow/blue
• Black/White
If you tire one receptor, the other while fire!
Energy Senses—Hearing/Audition
• Sound waves are vibrations in the air and
are collected by the ear.
• These waves have amplitude and
frequency
• Amplitude determines loudness
• Frequency determines pitch
Energy Senses--Audition
• Sound waves are collected by the pinna or
the outer ear.
• The waves travel down the ear canal or
the auditory canal.
• They reach the tympanic membrane or the
eardrum.
• This is where swimmer’s ear occurs.
Auditory Canal
Energy Senses--Audition
• The sound vibrations move onto the 3 little
bones or ossicles—first the Hammer
(malleus), next the Anvil (Incus), and last
the Stirrup (Stapes).
• This is where ear infections—Otis media
occur— Eustachian tube.
• The vibrations are next transmitted to the
oval window which is like the tympanic
membrane or eardrum.
Energy Senses--Audition
• The oval window transfers to the sound waves to
the cochlea—fluid filled snail looking structure.
• The sound waves cause the fluid to move.
• The floor of the cochlea is called the basilar
membrane— it is lined with hair cells which are
connected to the Organ of Corti which are
neurons activated by the movement of the hair
cells. These impulses are sent to the brain via
the auditory nerve.
Energy Senses--Audition
• Pitch Theories—
– Place Theory—where it is
– Frequency Theory—the rate of it
Energy Senses--Audition
• Deafness
– Conduction Deafness— outer ear or middle
ear, for example-- Patient with stirrup
degeneration will eventually not be able to
hear
– Nerve Deafness— hair cells in the cochlea
are damaged usually by loud noise
Energy Senses--Audition
• Sound localization— how do we detect
where a sound is coming from?
Experiment and figure it out!
• If a sound gets to one ear faster, then you
know which direction it is coming from—
your ears and your brain can do physics
even if you can’t!
Energy Senses--Touch
• Touch is very important to our human
existence—it helps you live longer!
– Harry Harlow
– Kangaroo Care
– Free Hug Movement
Energy Senses--Touch
• Pain, pressure, warm, cold
• Brain can interpret intensity from a light
touch to a hard blow
• Nerve endings are more concentrated in
different parts of our body with fingertips
being the most sensitive.
– Sensitivity TEST
Energy Senses--Touch
• Gate-control theory— some pain
messages have a higher priority
Example--itching and scratching
• Endorphins (nature’s pain killers) can
swing the gate shut.
Chemical Senses
• We are not strong in this sensory area.
Why?
• What animals would be better than us?
Why?
• What would their brains look like?
Chemical Senses—
Taste/Gustation
• Chemicals in food like salt are absorbed using saliva by
taste buds which are housed in papillae.
• The more densely packed your tastebuds the more
sensitive you are to that taste.
• For example, I hate bitter things like coffee and alcohol
which means that I might have more bitter buds in my
tongue. I love really sweet things, so maybe I don’t have
that many sweet buds.
• You have sweet, salty, bitter, sour, and umami on your
tongue and in your mouth.
• Make a taste map of your tongue.
Chemical Senses—Smell/Olfaction
• Flavor is caused by an sensory interaction
of taste and smell
• Molecules settle into a mucous membrane
in our nose called the olfactory epithelium
• There we have about 100 different
olfactory receptors which are linked to our
olfactory bulb.
Chemical Senses--Pheromones
• Vomeronasal Organ senses somewhat
undetectable chemicals called pheromones that
may influence human behavior
– Babies can identify their mother’s smell right after
birth
– Women who are close, tend to menstruate together
– Women can smell if a man is sick and will not want to
mate
– Women tend to be most attracted to the indiscriminate
smells of a man’s sweat and men tend to be most
attracted to things surrounding food like pumpkin and
vanilla
Chemical Senses--Olfaction
• Nerve fibers from the olfactory bulb
connect to the brain at the amygdala and
then to the hippocampus, part of the limbic
system.
• The other senses are all processed
through the thalamus before being sent
on.
• This may explain why smell can be such a
powerful trigger for memories.
Body Position Senses—
Vestibular/Balance
• Vestibular sense tells us how our body is
oriented in space.
• Three semi-circular canals in the inner ear give
the brain feedback about body orientation.
• Fluid in the canals move when you move.
• When the brain receives confusing messages it
causes you to get sick.
• Motion sickness, sea legs, rollercoasters,
spinning on a tire swing, etc.—what else?
Body Position Senses—
Kinesthetic/Movement Sense
• Receptors in our joints and muscles send
messages to our brain about our limbs
which helps us keep track of our body.
• You can close your eyes and touch your
toes and Peyton Manning can throw to his
receiver blindfolded.