Transcript Ch 8: Special Senses

Ch 12: Special Senses
Nose, Eyes, Ear, and Tongue
External Anatomy of the Eye
• Eyelids: Protection, Lubrication
• Eyelashes: Protection
• Glands: Meibomian and Ciliary
–Meibomian: Oil glands, modified
sebaceous glands on eyelids
–Ciliary: Modified sweat glands.
Third eye-lid
Gathers dust
and produces
eye crispies.
In other animals
It can cover the
Eye.
What is the Lacrimal apparatus and
what does it do?
• Lacrimal apparatus. Fig 12.5
– Lacrimal glands: release tears
– Lacrimal ducts (eyelid) and canals (nose)
– Nasolacrimal ducts: empties into the nose
• Lacrimal Secretion: Tears have
antibodies and lysozyme. Cleans,
moistens.
• Why is it called a healthy cry?
Lysozyme
What are the Muscles of the eye
and how do they move it?
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Lateral rectus: Moves eye laterally
Medial rectus: Moves eye medially
Superior rectus: Moves eye up
Inferior rectus: Moves eye down
S & I Obliques
Fig 8.15, 197
Fig 12.7, pg 296
Practice using
The Eye Muscles
What are the internal structures
of the eye? Pg. 295, Fig 12.6
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Sclera: white of the eye
Cornea: Clear
Iris: colorful part of the eye
Pupil: Opening of the Iris
Lens and ciliary body: Ciliary body holds
the lens in place. The lens focuses light on
the back of the eye.
What fills the inner eye? Pg 298
• Aqueous Humor: Circulates from the
cornea to the Lens through the canal of
Schlemm.
• Vitreous Humor: In the space behind the
lens. Keeps the eyes shape, and keeps
intraocular pressure stable.
• Floaters?
• Glaucoma?
What lines the back of the eye?
• Retina: photoreceptor layer
– Rods: Black and white
– Cones: Color
• Choroid coat: Dark, vascularized layer.
Absorbs light. *Non-humans are different
• Sclera: Thick, white covering
How do you see? Pg. 299
• .
How we See
Details of Vision
Adam
Light travels through the…
Cornea to the Aqueous humor to the Pupil to
the lens.
In the Lens light is bent so that it will hit the
Retina of the eye.
To get to the Fovea Centrals light must
continue to pass through Vitreous humor.
Light then hits the Retina where Rods and
Cones interpret the image and sends it to
the Optic nerve to the brain.
Where is your vision the best and
the worst?
• Worst vision: The blind spot. To find
your blind spot go to pg 297 in the book.
– Blind spot is where the optic nerve takes the
image to your brain. There are no rods or
cones here. Your brain just fills in the gaps.
• Best vision: Fovea Centralis. Lateral to
the blind spot, only contains cones. This
is the spot of greatest visual acuity.
Light
Lens
Focal
plane
Emmetropia
(normal)
Myopia
(nearsightedness)
Hyperopia
(farsightedness)
Presbyopia
(aged)
Why do cones see better than
rods?
• See Fig 12.8
• Many Rods, one nerve = blurred edges.
• One Cone, one nerve = crisp lines.
– Which do you think causes Night Blindness?
• What type of cones do you have:
– Blue cones: see blue light
– Green cones: see green light
– Red cones: see red and green light.
Component colors are detected by cone cells in the
retina.
All colors in the visible spectrum can be represented as a
combination of red, green, and blue. In the retina, a fullcolor image is broken up into component colors by cone
cells specialized to detect red light (long wavelength),
green light (med. wavelength), blue light (short
wavelength).
What is colorblindness?
• The lack of a type of cone, or all cones.
• Sex-linked gene.
• Men suffer from color blindness more
often than females.
Vision of the
Colorblind
How is Lasik’s
performed?
Steps
to
LASIK
Surgery
Steps
to
LASIK
Surgery
Illusions
Optic nerve
Optic chiasm
Optic tract
Lateral geniculate nucleus
Optic radiation
More Illusions
Primary visual cortex
The Ear
Pg. 302
& 303
Functions: Hearing and
Equilibrium…………….
External Ear
How the
Ear hears.
• Auricle
• External Auditory Meatus-2.5 cm long
leads to Middle ear
The Middle Ear
• Tympanic Cavity: air-filled space
• Tympanic Membrane- ear drum
• Pressure changes cause it to vibrate, enhances
the sound wave
• Auditory Ossicles: smallest bones in the
body. Malleus, incus, and stapes.
• The Stapes vibrate at the oval window
causing fluid in the inner ear to move,
stimulating hearing receptors.
STAPES
INCUS
MALLEUS
Auditory tube mucous membranes
connect directly with the middle ear linings.
Thus, mucous membrane infections of the
throat may spread through these tubes and
cause a middle ear infection.
Question: Why is it important to keep a
babies head up when bottle feeding?
Xylitol gum and chewing it
could help prevent ear
infections.
How the
Tubes work
Inner Ear. Pg. 304
Cochlea: hearing
• Oval Window: the stapes vibrates this in
order for your nerves to fire and for you to
Quick Review
hear sound.
Sound on Cochlea
Review of the Ear:
In depth on Cochlea
And Hearing
Inner Ear: pg. 306 - 307
• Semicircular Canals: maintain equilibrium
The vestibular system
Hearing Illusions
Sex and
Smell
The Nose. Fig 12.3
• Smells using Olfactory Receptors
– Yellow-brown mass located at the top of each
nasal cavity
– Size of a postage stamp.
Factoid:
These swirl the
Air so that
Dust and germs
Stick to the
Mucus.
How we smell
How do olfactory receptor cells
smell?
• Use Olfactory Hairs
– Must be covered in mucus
– Chemicals dissolve in mucus
– Trigger nerve
• Olfactory Nerve
– Connects to the Olfactory Bulb in Brain.
Travels to temporal lobe for interpretation.
– Tied to the limbic system (emotional system)
of the brain. Smells stimulate memories.
Interesting Nose facts
• Olfactory neurons that are over stimulated shut
off. (Can’t smell X after a while.)
• Anosmias: loss of smell due to head injuries,
nasal cavity inflammation (cold, allergy,
smoking) or age.
– Often caused by a zinc deficiency
• Olfactory auras: epileptics may have smell
hallucinations before a seizure.
• Because dust in space does not settle
Austronoauts sneeze about 100 times a day!
Factoid:
The Tongue.
Fig. 12.4
You can detect
and distinguish
between 10,000
odors, but
only 5 tastes.
.
How Do You Taste?
• Gustatory cells- respond to chemicals
that are dissolved in saliva
• Taste buds- receptor sites for tastes.
Most are on the tongue. Some are on the
roof of the mouth and cheeks
• Papillae- on the sides of this structure is
where taste buds are found
How do you
Taste?
Basic Taste Sensations
• Sweet- sugar, OH- groups
• Sour- acidic, H+
• Umami- meaty or savory
• Bitter- alkaloid bases, very few H+ bonds
• Salty- metal ions
The science
Of
Picky Eaters
What effects taste?
• Temperature
• Smell
• Texture
• Genetics