Notes on Ch. 14 - Senses
Week 12 notes
Unit Outcomes
 Explain other ways that humans sense their environment and their spatial
orientation in it
› olfactory receptors, proprioceptors, taste receptors, receptors in the skin
 Describe the structure and function of the parts of the human eye
› cornea, lens, sclera, choroid, retina, rods and cones, fovea centralis, pupil,
iris, and optic nerve
 Describe the structure and function of the parts of the human ear
› pinna, auditory canal, tympanum, ossicles, cochlea, organ of Corti,
auditory nerve, semicircular canals, and Eustachian tube
Receptors
 Table 1 pg 446
 Figure 2 pg 447
Taste
 Taste receptors are concentrated in _______________________ on our tongues
 Specific chemicals stimulate receptors
› 5 types: ________, _______, _______, _________ and __________
 each cell (each taste bud)can detect all tastes, but is particularly responsive to a
certain type/chemical
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Notes on Ch. 14 - Senses
Eye Structure
 Has 3 separate layers
› _______________
› _______________________________
› _______________
Sclera
 This is the white of your eye
 It is the ____________________ layer and its function is to ______________ and
maintain the ___________ of the eye
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Notes on Ch. 14 - Senses
 It includes the ___________ and _____________________________
Cornea
 Front portion of _______________
 Clear
 Strongly curved
 Starts to __________________ light
Aqueous Humour
 _____________
 Supplies nutrients to cornea
 Fills _____________ (anterior) eye cavity
Choroid Layer
 This is the _____________________ layer of your eye
 It contains the _____________________ for the retina
 It includes the __________, ___________, __________, ____________________,
and ___________________________________
Iris and Pupil
 Iris is the ________________ part that makes up the front of choroid layer
 It contains muscles to change _________ diameter
› Circular muscles close pupil
› Radial muscles open pupil
 The ________ is just a hole in the iris that light comes through
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Notes on Ch. 14 - Senses
Ciliary Muscles (Body)
 Smooth muscle that changes _________________________
 Attaches to ligaments which are connected to lens
 Muscle contraction changes shape of lens
 Secretes aqueous humour
Lens
 _______________ light on retina
 Controlled by muscles of ciliary body
 Lens _________ for distant objects
› Image is ______________ when light passes through

Image is projected on retina upside-down.
 The changing __________ of the lens will focus the image on the retina
Vitreous Humour
 __________, jelly-like material
 Maintains the ___________ of the eyeball
 Helps ___________ ___________ onto the retina
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Notes on Ch. 14 - Senses
Retina
 This is the __________________ layer of your eye
 It contains ___________________ and has 4 different layers of cells
› Pigmented epithelium
› Light-sensitive cells (__________________ ____________________)
› Bipolar cells
› Cell of the ___________________ _____________________
 Light-sensitive cells (sensory receptors)
› _________ which are cells for low-intensity light
› _________ which are cells for high-intensity light and identify _________
› Cones are concentrated in the __________ ____________ located at the
back of the eye
› Rods are located around the ________________ of the fovea.
› There are no receptors (rods and cones) where the optic nerve and retina
join

___________ _________
Pathway of Light
 Light __________ the retina through the pigmented epithelium, which helps
focus the light onto the _______ and ________.
 The signal is then sent through the ______________ cells to the cells of the
____________ __________ which transmit the message to the brain.
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Notes on Ch. 14 - Senses
Chemistry of Vision
 Rods contain _________________, a light senstive pigment
› Light hits the rhodopsin and causes an _________ ___________ in the
rod.
› Neurotransmitters communicate this stimulus (AP) to the bipolar cells and
then to the optic neurons
› Rhodopsin is sensitive to light and breaks down in high light intensity, so it
works best in _________ light intensity situations
› Negatively affected by Vitamin A deficiency.
 Cones have a less sensitive pigment, so they work better in _________ intensity
situations, allowing you to see __________.
 Each cone is sensitive to one of the three primary colours of source light
› Red
› Blue
› Green
 Combinations of cones being stimulated by different wavelengths allows you to
perceive different colours
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Notes on Ch. 14 - Senses
Colour Blindness
 This happens when one or more types of cones are _______________
 The most common type is red-green colourblindness where the red sensitive
cones are defective
Afterimages
 __________ = you can see the shape of a camera’s flash after you close your
eyes.
› Image has been “burned” onto your retina
 ___________ = color reversal
› caused by fatigue of cones responsible for particular colors, while others
continue to fire
Accommodation
 Normal focusing of light
› __________ bends light to _________: light slows down as it travels
through the cornea (dense material) = refraction of light inward toward
lens. Lens is thicker in middle than edges, so light bends to a focal point
(center of _____________)
 Viewing close up
› ciliary muscle __________ and lens becomes ___________ = additional
bending of light. Pupil constricts to focus the image (light is focused more
onto the fovea centralis)
 Viewing farther away
› ______________ of ciliary muscle causes lens to _________ out. Pupil
dilates to let in more light
 As you age: layers of protein cover the lens, hardening it so it is less flexible; more
difficulty accommodating for close up (reading).
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Notes on Ch. 14 - Senses
Vision Defects
 Near-Sightedness (________________)
› Eyeball is __________ ____________
› Rays from distant objects focus in front of the ____________
› Myopia can be corrected using a concave lens.
 Far-Sightedness (_________________________________)
› Eyeball is _________ ______________
› Rays from near objects focus ____________ the retina
› Hypermetropia can be corrected with a convex lens
 Glaucoma
› Buildup of ___________ humour
› Increases _______________ in the eye which causes retinal ganglion cells
(nerve cells) to die
› Results in loss of vision
 Cataracts
› __________ becomes opaque (can’t see through it)
› Light can’t pass through
› Can remove the lens and wear strong prescription glasses
 Astigmatism
› Lens or cornea is irregularly ______________
› Light doesn’t ______________ on back center of retina (fovea centralis)
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Notes on Ch. 14 - Senses
Ear Structure
 The ear is made up of three main structures
› _________ Ear

____________ sound waves

Transfers sound waves to middle ear
› _________ Ear

____________ sound waves

Transfers sound waves to inner ear
› _________ Ear

Turns ________________ ____________ (from sound waves) into
______________ ____________ which are sent to the brain
through the auditory nerve
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Notes on Ch. 14 - Senses
Outer Ear
 The outer ear consists of the __________ and the ___________ _________
 __________
› External ear flap
› Collects sound
 ___________ ___________
› Carries sound to the eardrum
› Has sweat glands that produce ear wax
 Tympanic membrane (____ _______)
› Thin tissue layer that receives sound vibrations
› Sends the vibrations from the sound waves into the middle ear
Middle Ear
 The middle ear consists of the ___________ and _________________ _______
 Ossicles
› Consists of three small bones that amplify and carry sound from tympanic
membrane to the oval window of the cochlea

_________ (hammer)

_________ (anvil)

_________ (stirrup)
 Sound vibrations transfer from the ________________ _____________ to the
malleus, which then hits the incus which hits the stapes which vibrates against
the membrane covering the ________ ___________ of the cochlea
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Notes on Ch. 14 - Senses
 Sound is ________________ by concentrating the sound energy from the
tympanic membrane to the smaller oval window
 ______________ tube
› Does not help with hearing
› It is an air-filled tube that equalizes _______________ between the
external and internal ear
› Where your ears “pop”
Inner Ear
 The inner ear consists of the ______________, _________________ _______
and the cochlea
 Vestibule (for __________)
› Involved in ___________ equilibrium/head positiion
 Semicircular canals (for ___________)
› Involved in _______________ equilibrium/body movement
 Cochlea (_________________)
› Coiled structure that turns sound waves into __________ ___________
› Contains the __________________________________
 Has sound receptors where waves become impulses
 Hair cells attached to ________________ _________________
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Notes on Ch. 14 - Senses
Cochlea
 Movement of __________ in the cochlea causes the basilar membrane to vibrate
› Different pitches of notes make different areas of membrane vibrate
 Small hairs (______________) are attached to the basilar membrane
 The hairs rub and bend against the ________________ membrane
 The bending generates a sensory nerve impulse that is sent to the ___________
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Notes on Ch. 14 - Senses
Hearing Summary
 Sound _________ push against _______________ membrane; these vibrations
are passed onto the _____________ (malleus then incus and finally stapes).
 The ossicles concentrate and ____________ the _______________ (exerting
greater force by concentrating the energy in a very small area).
 ________ _____________ receives vibrations from stapes which causes the oval
window to move in and out. This results in the round window (below it) to also
move in and out (in alternation with oval window). The two windows moving in
and out cause fluid to move in the inner ear.
 The cochlea receives __________ ____________ and converts them into
_______________ impulses.
 ___________ waves move the basilar membrane, the hairs on the
membrane brush against tectorial membrane and bend. This stimulates
_________________ __________ in the basilar membrane to send
impulses to auditory nerve then to brain.
Ear Safety
 Small muscles in your ears help protect your hearing
 When loud noises are around:
› Muscles attached to the malleus (hammer) contract and restrict intense
movements
› A second muscle contracts, pulling the stapes (stirrup) away from the oval
window, limiting inner ear damage
 This doesn’t work for sudden loud noises
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Notes on Ch. 14 - Senses
Hearing Loss
 ________________________ Hearing Loss
› Sound waves can’t enter ___________ _______
› caused by wax buildup, middle ear infection, or punctured eardrum
› Fixed by medical/surgical procedures
 ________________ Hearing Loss
› ___________ _________ is severed or damaged or hair cells of the
cochlea are damaged or dead.
› caused by aging, loud noises, head trauma or genetic conditions
 Hearing Aids
› pick up sound (microphone), amplify it and transmit it to eardrum
› won’t work for Sensorineural hearing loss (vibrations can’t be transmitted
to brain)
 Cochlear Implants
› does not make sounds louder or clearer
› bypasses damaged parts and converts sounds into electrical impulses that
are sent to the brain.
› has a microphone (picks up sounds), a speech processor (selects and
arranges sounds), a transmitter and receiver/stimulator receive signals
from the speech processor and convert into electrical impulses. Electrodes
send them to the auditory nerves.
 * Doesn’t replicate exact sounds (like we hear them), provides sounds that allow
person to interpret their environment. Over time, person learns to decipher
impulses and can understand speech.*
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Notes on Ch. 14 - Senses
Equilibrium and Balance
 _____________ equilibrium (Am I upside down)
› Movement along one plane (vertical or horizontal)
› Detected by the _______________
› Involves two other structures

___________

___________
› Fluid filled
› Contains tiny ___________ (cilia)
 When the head is upright: calcium carbonate crystals in the fluid (___________)
don’t move = fluid doesn’t move = cilia don’t move
 When the head is bent forward: the otoliths shift _____________, pulling on the
fluid.
 This causes the _______ to bend which _______________ the nerve cell.
 Sends a nerve __________ to brain (cerebellum) informing of head position
relative to gravity
 _____________ Equilibrium (Moving forwards or backwards, spinning, flipping
around)
 Detected by the _______________________ ______________
› Has 3 different fluid filled rings

Vertical

Horizontal

Diagonal
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Notes on Ch. 14 - Senses
 Each canal has an ampulla (pocket) that holds a cupula
 When you move, __________ in the semicircular canals moves, bending
________ (that are on hair cells found in the cupula).
› Results in nerve signals sent to __________.
 Rapid, continuous movement of the fluids causes motion sickness
****Table 1, pg 461****
Formative Week 12
Do the following questions for practice
Pg 448 #1,3
Pg 455 #1,4
Pg 458 #2
Pg 466 #1-14, 20-23
Send me pg 448 #1,3; pg 466 #1,4,7,10
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