Download Hearing and Sound - County Central High School

The Eye and the
Ear
Before we begin...
What questions do you have about the eye? Write
down a minimum of 2 questions in your notes.
What about the ear? Again, write down a minimum
of 2 questions in your notes.
The Senses
As we have learned, sensory neurons carry
information from our internal and external
environments to our CNS.
Specialized sensory receptors transmit this
information to sensory neurons.
The Senses
Light-sensitive receptors in the retina are
stimulated by light.
Specialized temperature receptors detect cold
while other receptors detect heat.
Specialized chemoreceptors in the blood detect
CO2 levels
The Senses
Sensory receptors convert one source of energy
into another.
For example taste receptors convert chemical
energy into an action potential (electrical energy).
Sensory receptors tend to be grouped together
within specialized sensory organs (eye, ear, etc.).
The Senses
The grouping of sensory receptors allows for summation
to occur and threshold levels to be reached quicker.
The Senses
Despite an incredible collection of specialized
sensory receptors, much of your environment
remains undetected.
What you detect are stimuli relevant to your
survival.
The Senses
Sensory adaptation occurs when a receptor has
become accustomed to a stimulus.
This enables us to function in life without feeling
every single stimulus on our skin all the time.
Taste and Smell
Taste receptors allow you to tell the difference
between things that you can eat and things you
can’t.
These receptors are found in different placed
depending on the species:
- Humans - tongue
- Octopus - tentacles
Taste and Smell
Each taste bud is then associated with a different
taste.
Structures of the Eye
You have 20 minutes to fill in the structures of the
eye chart. Use your textbook or your phones to
find what the function of each structure is.
Blind Spot Test
Take the paper I have just handed out to you.
Hold it up in front of you. Close your left eye and
with your right eye, stare at the cross. Slowly move
the paper towards and away from your face. The
dot on the other side should disappear. This blind
spot is where your optic nerve attaches to your
retina. Try the other eye!
Afterimage
An afterimage is an image that appears in your
vision even after the original image is gone.
Take a look at the picture on the next slide. Look at
the three dots on her nose until I tell you to stop.
As soon as I say stop, look at a white piece of
paper and blink quickly. What do you see?
Chemistry of Vision
The eye contains millions of rods and cones in
the retina.
Rods contain light sensitive pigments called
rhodopsin.
Cones contain similar pigments but are less
sensitive to light.
Chemistry of Vision
When light hits a rhodopsin molecule, it divides
into two components:
- retinene: pigment portion
- opsin: protein portion
This division triggers an action potential that
releases neurotransmitters transmitting information
along the optic nerve
Chemistry of Vision
Rhodopsin breaks apart quickly in bright light and
therefore works best in low light.
This is why rods are referred to as your ‘black and
white’ vision.
Cones function better in bright light and allow you
to see colour.
Focusing on the Image
When light enters the eye, it is bent by the cornea
towards the pupil.
The cornea directs light towards the lens, resulting
in further bending. As it goes through the lens, the
light is bent towards a focal point.
Focusing on the Image
Due to the light bending (refracting) twice, the
image imprinted on the retina is inverted (upside
down).
Ciliary muscles attached to the lens change its
shape to focus the light in different ways.
Focusing on the Image
Adjustment of the lens to things near and far is
called accommodation.
This accommodation changes as you get older.
The lens hardens and it can’t be changed as
easily leading to blurry vision.
Focusing on the Image
When images are viewed up close, the pupil
constricts to bring the object into focus.
The Inuit people were aware of this principle when they
made eyeglasses by drilling holes in whale bones.
Light through narrow openings results in sharper
focus
Vision Defects
There are 5 different defects listed in your textbook
(pages 453-454).
Explain what they are and how they affect a person’s
vision. How does someone become affected by each
defect?
Questions?
Go back to your questions you made at the beginning
of the notes. Have we answered them? Do you have
new questions? Write them down if you do.
The Ear
Fill out the structures of the ear sheet that you have in
your notes. Use your phone or your textbook to help
you, you have 20 minutes.
Hearing and Sound
Sound is a form of energy that must be changed to
electrical energy for us to interpret it.
Hearing begins when sound waves push against the
tympanic membrane. The vibrations are passed on to
the ossicles. These three bones triple the force of the
vibration.
Hearing and Sound
Muscles that connect the ossicles act as a safety net.
When intense sound occurs, these muscles contract,
lowering the amount of vibrations that can occur
thereby lowering the impact on the inner ear.
The ossicles pass the vibrations to the oval window
causing it to push inward. As the oval window pushes
in, the round window pushes out.
Hearing and Sound
This movement triggers waves of fluid within the inner
ear.
The cochlea receives the fluid and converts them to
electrical impulses.
The organ of Corti in the cochlea contains specialized
hair cells anchored to the basilar membrane.
Hearing and Sound
The hair cells respond to vibrations.
https://www.youtube.com/watch?v=Xo9bwQuYrRo
The movement of hair cells causes sensory nerves to
be stimulated. Auditory information is then sent to the
temporal lobe via the auditory nerves.
Hearing and Sound
Hearing and Sound
The inner ear can identify both pitch and loudness.
Close to the oval window, the basilar membrane is
narrow and stiff. This is activated by high frequency
waves registering high pitch sounds.
Further from the oval window, the basilar membrane is
more flexible registering low frequency sounds.
Hearing and Sound
Getting hit in the
head hard can send
vibrations through
your ear that can be
interpreted as sound.
Hearing and Sound
How well can you hear?
https://www.youtube.com/watch?v=VxcbppCX6Rk
Equilibrium
Balance consists of two components: static and
dynamic equilibrium.
Static equilibrium involves movement along one plane
(horizontal/vertical)
Dynamic equilibrium provides information during
movement.
Static Equilibrium
Head position is monitored by two fluid filled sacs saccule and utricle
Tiny hair cells line these sacs.
Cilia from the hair cells are suspended in a gelatinous
material that contains small calcium carbonate
granules called otoliths.
Static Equilibrium
When the head moves, the otoliths brush against the
cilia causing them to bend.
The movement of cilia stimulates the sensory nerve,
and information about head position is relayed to the
cerebellum for interpretation.
Static Equilibrium
Dynamic Equilibrium
While you are moving, balance is maintained by the
three fluid filled semi-circular canals.
Each canal contains a pocket called an ampulla that
holds a cupula.
Rotational stimuli cause the fluid to move bending
cilia attached to hair cells in the cupulas.
Dynamic Equilibrium
Stimulation of hair cells sends impulses to the
cerebellum.
Rapid movement of fluid in the canals can cause
motion sickness.
Hearing Loss
What are 2 ways that hearing loss can be treated?
Use your phone and textbook to answer the question.