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Sensory Organs: The Eye
Reading Guide
1. What is a sensory receptor and name at least 3 areas where sensory receptors are
present (just think of how you use your 5 senses)
2. Sensory Adaptation, what is it and give 2 examples.
3. Draw a diagram of the eye and label it. You should know the function of all the
major parts.
4. Differentiate between rods and cones. What type are you likely to use more
frequently at night?
5. Why is the fovea centralis important for seeing well?
6.
a. Explain how light is focused onto the retina by various parts of the eye.
b. Explain how we can focus on objects when they are further away. Closer?
c. What is the process in part (b) referred to as? Do we always used this
process?
7. You should also know and understand various types of vision defects as listed on
pgs 442-443.
Sense Organs: The Ear
Reading Guide
1. What is the role of the pinna?
2. As sound waves enter the auditory canal, what is the first membrane they strike?
3. After striking the structure mentioned in (2), the vibrations are then passed along
what structures?
4. What is the role of the Eustachian tube
5. What structure maintains head position?
6. As the vibrations strike the oval window, the vibrations are then sent through fluid
in what structure?
a. In a sentence, how are the vibrations here sent to the brain? To what part
of the brain?
7. Briefly describe how we can differentiate between high and low pitched sounds.
8. how do the semi circular canals help us keep our balance? Briefly describe how it
does this. (hint: figure 5)
9. How is the most common type of hearing loss caused?
The eye
1. sensory receptors are highly modified ends of sensory neurons. Areas with
sensory receptors include your tongue, skin, ear, and nose.
2. sensory adaptation occurs once the receptor becomes accustomed to the stimulus.
This is why you may not smell a foul smell after a while, even though it is still in
the air.
3. .
4. rods: operate in dim light to detect black and white. Cones: operate in bright light
to detect colour. You would likely use rods more at night.
5. fovea centralis is important for seeing well because it contains many cones packed
close together.
6. light is first diffracted towards the pupil by the cornea. Light is then diffracted
towards the retina by the lens. An image needs to be focused on the retina in order
to see a sharp image.
a. Accommodation is the process of our ciliary muscles making the lens
thicker (for more diffraction) or thinner (for less diffraction). The varying
diffraction changes where the image is focused (ideally it will be focused
on the retina).
7. see textbook
the Ear
1. the pinna acts like a funnel, channeling sound waves into the small canal of the
ear.
2. the tympanic membrane
3. ossicles: mallus, incus, stapes.
4. Eustachian tube equalizes pressure between the external and internal ear.
5. Vestibule
6. through the inner ear.
a. Fluid Vibrations are sent through the inner ear and are received by the
cochlea and the cochlea converts the vibrations into electrical impulses
(action potential) which are then sent to the temporal lobe.
7. the narrowest area of the cochlea is activated by high-frequency waves which
contain enough energy to stimulate the rigid hairs. Low frequency waves
simulate hairs further along the cochlea. See animation from website.
8. the semi circular canals are fluid filled and lined with tiny hairs. Movement of the
fluid causes the hairs to bend, and based on the movement of these hairs our brain
interprets the movement.
9. hearing lost is most commonly caused by high intensity sound waves, carrying a
lot of energy literally tear the tiny hairs in our ear off.