Special Senses

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Special Senses
Olfactory Sense (smell) I. Olfactory receptors
are located in the superior portion of the nasal
cavity. (figure 40.2 page 721) II. How do we
smell? A. Gaseous molecules from substances
dissolve in mucus layer B. Stimulate neurons
that terminates in the cerebral cortex. C.
Adaptation is rapid, but memory is good.
Gustatory Sense (Taste) I. Taste buds are located
on the tongue (in or on Papillae), on the soft
palate and in the throat. (Figure 40.1 on page
720) II. Can only be stimulated by molecules in
solution. III. What are the four taste
sensations? IV. These are not localized.
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Visual Sense
I. Accessory Structures A. Eye brow and lashes
protect the eye from excessive light, sweat,
dust other falling debris B. Eye lids spreads
tears over eyes, shades eyes for sleep and
protect the eye from foreign objects.
C. Lacrimal Glands and ducts 1. Located superior
to the eye ball 2. Composition of tears a.
water, salt, mucus, lysozyme (bacterial
enzyme). 3. Function of tears a. protection
both physically and chemically.
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II. Anatomy of the Eye Ball (1 diameter) You
must have drawing of eye in your notes. A.
Fibrous Tunic (Outer Layer) 1. Cornea a.
Clear, protein b. passage way for light c.
no blood vessels-O2 from atmosphere.
Cornea
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2. Sclera- white of the eye provides shape and
protects inner parts.
Sclera
Posterior Cavity (Vitreous Humor)
Canal of Schlemm
Anterior Cavity (Aqueous Humor)
3. Canal of Schlemm a. Located at the edge of
the cornea and the sclera. b. Drainage pathway
for aqueous humor c. Humor drains from the
anterior cavity into the blood stream. 4.
Glaucoma- an increased pressure in the eye caused
by an accumulation of aqueous humor.
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B. Vascular Tunic (Middle Layer)
1. choroid a. dark brown layer that is highly
vascularized. b. nourishes the retina. c.
absorbs reflected light.
Ciliary Muscle
Choroid
Ciliary Process
2. Ciliary process and Ciliary Muscle a. ciliary
process produces aqueous humor. b. ciliary
muscle flexes and relaxes the lens for far and
near vision. c. With age the lens becomes less
flexible and farsightedness results.
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3. Iris
a. controls the amount of light entering the
eye. b. controlled by two sets of muscles.
Circular muscles constrict the pupils. Radial
muscles dilate the pupils.
Iris
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C. Retina (inner layer) (Figure 40.8 on page 726)
1. Responsible for forming an image.
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D. Retina (continued)
2. Nervous Layer a. Photoreceptive layer -
contains rods and cones which absorbs light and
forms an image. b. Bipolar cell layer c. Ganglion
layer their axons form the optic nerve.
Optic Nerve
Ganglion layer
Bipolar cell layer
Photoreceptive layer
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D. Retina (continued)

• Rods specialized for dim light, allows you to
  see shade, shapes and movement, but cannot
  produce a clear, sharp, colored image.

• Cones work only in bright light, specialized
  to see color and form a sharp clear image, there
  are about 10-20 times more rods than cones.
• Most of the cones are all in one area called
  the central fovea

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III. How do rods work?
Light
Rhodopsin (visual purple)
Slow
Scotopsin
Retinal
Depolarization
How do carrots help your vision?
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IV. How do cones work?

• Cones work the same as rods except
• Bright light breaks down the photopigment into
  photopsin retinal.
• You have 3 different kinds of cones.
• Each kind of cone is sensitive to a different
  color of light (red, green and blue).

V. Problems with Vision A. Myopia -
nearsightedness, caused by oblong eye
ball. Corrective lens move the focal point back
onto the retina. B. Hypermytropia - far
sightedness C. Astigmatism - an irregular surface
on the cornea or lens.
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The Ear

• Anatomy of the ear (three layers)
• Draw figure 40.9 on page 728 in your notes

• Outer Ear- consists of auricle and external
  auditory canal.
• Auricle (pinna) - made of elastic cartilage
  covered by thin skin.
• External Auditory canal - tube leading from
  auricle to tympanic membrane.
• skin lining the canal has glands that secrete ear
  wax

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B. Middle Ear (tympanic cavity)

• The ear drum (tympanic membrane) is the border
  between the outer and middle ear.
• The middle ear joins with the nasopharynx via the
  eustachian tube (auditory tube).
• Eustachian tube equalizes pressure on both sides
  of the external tympanic membrane.

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B. Middle Ear (tympanic cavity)

• It has 3 small ossicles (bones) malleus, incus,
  and stapes.
• The malleus (hammer) attaches to tympanic
  membrane.
• The incus, (anvil) located between the malleus
  and stapes.
• The stapes (stirrup) attaches to the oval window.

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C. Inner Ear - (osseous labyrinth)

• Vestibule - central portion of inner ear
• this portion senses gravity changes as well as
  linear and angular acceleration.

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C. Inner Ear - (osseous labyrinth)

• Three semicircular canals - projects from the
  posterior end of vestibule.
• It is stimulated by sudden movements or changes
  in the rate or direction of movement.

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3. The cochlea - bony cone extending anterior
from the vestibule.

• Organ of Corti is the organ responsible for
  hearing.
• Cochlear cavity has 3 chambers and the Organ of
  Corti (page 729 figure 40.10)

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II. Physiology of Hearing

• Sound waves enter external auditory canal.
• Waves strike ear drum causing it to vibrate
  slowly for low frequencies, quickly for high
  frequencies.
• Malleus (connected to ear drum) begins to
  vibrate
• Which in turn vibrates the incus
• Then the stapes starts to vibrate.

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F. The stapes moves back and forth, pushing oval
window in and out.

• G. Movement of oval window causes waves in the
  thick liquid found in the ducts of the inner ear.

H. The waves are transferred from one duct to
another. Eventually producing waves in the
cochlear duct.
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These waves cause the movement of hair cells in
the organ of corti.
1. The hair cells, tectorial membrane and the
basilar membrane make the organ of Corti
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J. As the hair cells move the hair cells
depolarize and you hear.

• K. Low pitch sound stimulate movement near the
  apex of the cochlea, high pitch sounds stimulate
  the base of the cochlea.