Download Special Senses

Special Senses
The Senses
 General senses of touch
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 Special senses
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 Function of the lacrimal apparatus
 ___________________________________ the eye
 Empties into the nasal cavity
 Properties of lacrimal fluid
 Dilute _____________ solution (tears)
 Contains antibodies and lysozyme
 Extrinsic eye muscles
 _________ muscles attach to the outer surface of the eye
 Produce eye _____________________
Structure of the Eye
The Eye and Vision
 ______ of all sensory receptors are in the eyes
 Each eye has over a ___________ nerve fibers
 Protection for the eye
 Most of the eye is enclosed in a __________ ________
 A cushion of ______ surrounds most of the eye
Accessory Structures of the Eye
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 Tarsal glands lubricate the eye
 Ciliary glands are located between the eyelashes
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 Membrane that lines the eyelids
 Connects to the surface of the eye
 Secretes mucus to lubricate the eye
 Lacrimal apparatus
 _____________gland—produces
lacrimal fluid
 Lacrimal _____________—drain
lacrimal fluid from eyes
 Lacrimal _____________—
provides passage of lacrimal fluid
towards nasal cavity
 ___________________—empties
lacrimal fluid into the nasal cavity
 Layers forming the wall of the eyeball
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 Outside layer
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 Middle layer
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 Inside layer
Structure of the Eye: The Fibrous Layer
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 White __________________ tissue layer
 Seen anteriorly as the “___________________________”
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________________________, central anterior portion
Allows for ________________ to pass through
_____________ itself easily
The only human tissue that can be _________________
without fear of rejection
Structure of the Eye: Vascular Layer
 _________________ is a blood-rich nutritive layer in the
posterior of the eye
 _________________ prevents light from scattering
 Modified anteriorly into two structures
 _________________ —smooth muscle attached to lens
 ____________—regulates amount of light entering eye
 Pigmented layer that gives eye _____________
 Pupil—rounded __________________ in the iris
Structure of the Eye: Sensory Layer
 Retina contains two layers
 Outer __________ layer
 Inner __________ layer
 Contains receptor
cells
(photoreceptors)
 ________
 ________
 Signals pass from
photoreceptors via a two-neuron chain
 Bipolar neurons
 Ganglion cells
 Signals leave the retina toward the brain through the
______________ nerve
 ______________ (blind spot) is where the optic nerve leaves
the eyeball
 ______________ see images focused on the optic disc
 Neurons of the retina and vision
 Rods
 Most are found towards the __________ of the retina
 Allow ______ light vision and _____________ vision
 All perception is in ___________ tones
 Cones
 Allow for ___________ ______________ vision
 Densest in the ________________ of the retina
 _______________—area of the retina with only cones
 ____photoreceptor cells are at the optic disc, or blind spot
 Cone sensitivity
 ____________ types of cones
 Different cones are sensitive to different wavelengths
 Color _________ is the result of the lack of one cone type
Lens
 ____________ crystal-like structure
 Held in place by a suspensory ligament attached to the ciliary
body
 Cataracts result when the lens becomes hard and
__________ with age
 Vision becomes _________ and distorted
 Eventually causes blindness in affected eye
Two Segments, or Chambers, of the Eye
 Anterior (________________) segment
 Anterior to the lens
 Contains aqueous humor
 Posterior (_______________) segment
 Posterior to the lens
 Contains vitreous humor
Anterior Segment
 ________________ humor
 ______________ fluid found between lens and cornea
 Similar to blood _____________
 Helps maintain intraocular _________________
 Provides ________________ for the lens and cornea
 Reabsorbed into venous blood through the scleral venous
sinus, or canal of Schlemm
Posterior Segment
 _________________ humor
 _______________ substance posterior to the lens
 Prevents the eye from ________________
 Helps maintain intraocular pressure
Ophthalmoscope
 Instrument used to illuminate the interior of the eyeball
 Can detect diabetes, arteriosclerosis, degeneration of the
optic nerve and retina
Pathway of Light Through the Eye
 Light must be focused to a point on the ______________ for
optimal vision
 The eye is set for ______________ vision
(over 20 feet away)
 Accommodation—the _____________ must change
________ to focus on closer objects (less than 20 feet away)
 Image formed on the retina is a real image
 Real images are
 _______________ from left to right
 _______________ down
 _______________ than the object
Eye Reflexes
 Internal muscles are controlled by the
____________________ nervous system
 Bright light causes pupils to ______________ through
action of radial, circular, and ciliary muscles
 Viewing close objects causes accommodation
 External muscles control eye ____________ to follow objects
 Viewing close objects causes _____________________
(eyes moving medially)
A Closer Look
 ______________—eye focuses images correctly on the retina
 ______________ (nearsighted)
 Distant objects appear ____________
 Light from those objects fails to reach the retina and are
focused in _____________ of it
 Results from an eyeball that is too long
 ______________ (farsighted)
 Near objects are blurry while distant objects are clear
 Distant objects are focused ______________ the retina
 Results from an eyeball that is too short or from a “lazy
lens”
 _______________________
 Images are ___________________
 Results from light focusing as lines, not points, on the
retina due to unequal curvatures of the cornea or lens
Homeostatic Imbalances of the Eyes
Visual Fields and Visual Pathways
 Optic __________________
 Location where the optic nerves _______________
 Fibers from the medial side of each eye cross over to the
opposite side of the brain
 Optic __________________
 Contain fibers from the lateral side of the eye on the same
side and the medial side of the opposite eye
 Night blindness—inhibited rod function that hinders the ability
to see at night
 Color blindness—genetic conditions that result in the inability
to see certain colors
 Due to the lack of one type of cone (partial color
blindness)
 Cataracts—when lens becomes hard and opaque, our vision
becomes hazy and distorted
 Glaucoma—can cause blindness due to increasing pressure
within the eye
The Ear
 Houses two senses
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 Receptors are ____________________________
 Different organs house receptors for each sense
Anatomy of the Ear
 The ear is divided into three areas
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The Middle Ear (Tympanic Cavity)
 _____________________ cavity within the temporal bone
 Only involved in the sense of ____________________
 Two tubes are associated with the inner ear
 The opening from the auditory canal is covered by the
tympanic membrane
 The _______________________________ tube
connecting the middle ear with the throat
 Allows for equalizing ___________________ during
yawning or swallowing
 This tube is otherwise __________________
Bones of the Middle Ear (Tympanic Cavity)
 Three bones (_____________________) span the cavity
 ______________ (hammer)
 ______________ (anvil)
 ______________ (stirrip)
 Function
 Vibrations from eardrum move the _____________ 
_____________  _____________  _____________
Inner Ear or Bony Labyrinth
The External Ear
 Involved in __________________________ only
 Structures of the external ear
 __________________ (pinna)
 External acoustic meatus (______________________)
 Narrow chamber in the temporal bone
 Lined with skin and _______________________
(wax) glands
 Ends at the ____________________________
 Includes sense organs for
_____________ and
_____________
 Filled with _________________
 A maze of bony chambers within the
temporal bone
 _____________
 _____________
 _____________ ____________
Organs of Equilibrium
 Equilibrium receptors of the inner ear are called the
_____________ apparatus
 Vestibular apparatus has two functional parts
 _____________ equilibrium
 _____________ equilibrium
Static Equilibrium
 _____________ —receptors in the vestibule
 Report on the _____________ of the head
 Send information via the vestibular nerve
 Anatomy of the maculae
 Hair cells are embedded in the _____________
membrane
 _________(tiny stones) float in a gel around the hair cells
 Movements cause otoliths to ___________ the hair cells
Dynamic Equilibrium
 _____________ _____________ —receptors in the
semicircular canals
 Tuft of hair cells
 _____________ (gelatinous cap) covers the hair cells
 Action of angular head movements
 The cupula _____________ the hair cells
 An impulse is sent via the vestibular nerve to the
cerebellum
Organs of Hearing
 Organ of _____________
 Located within the _____________
 Receptors = hair cells on the basilar membrane
 _____________ tectorial membrane is capable of
_____________ hair cells
 Cochlear nerve attached to hair cells transmits nerve
impulses to auditory cortex on temporal lobe
Mechanism of Hearing
 Vibrations from sound waves move _____________
membrane
 Hair cells are _____________ by the membrane
 An _____________ ___________ starts in the cochlear nerve
 _____________ stimulation can lead to adaptation
Olfaction—The Sense of Smell
 Olfactory receptors are in the __________ of the nasal cavity
 Neurons with long _______________
 Chemicals must be ____________ in mucus for detection
 Impulses are transmitted via the olfactory nerve
 Interpretation of smells is made in the cortex
The Sense of Taste
 Taste____________ house the receptor organs
 Location of taste buds
 Most are on the _____________
 _____________ palate
 _____________
Taste Sensations
 _____________ receptors
(sugars)
 Saccharine
 Some amino acids
 _____________ receptors
 Acids
 _____________ receptors
 Alkaloids
 _____________ receptors
 Metal ions
 _____________
Chemical Senses: Taste and Smell
 Both senses use _____________
 Stimulated by chemicals in _____________
 Taste has _____________ types of receptors
 Smell can differentiate a _____________ range of
chemicals
 Both senses _____________ each other and respond to
many of the _____________ stimuli
The Tongue and Taste
 The tongue is covered with projections called papillae
 _____________ papillae—sharp with no taste buds
 _____________ papillae—rounded with taste buds
 _____________ papillae—large papillae with taste buds
 Taste buds are found on the sides of papillae
Structure of Taste Buds
 _____________ cells are the receptors
 Have gustatory hairs (long _____________)
 Hairs are stimulated by _____________ dissolved in
saliva
 Impulses are carried to the gustatory complex by several
cranial nerves because taste buds are found in different areas
 Facial nerve
 Glossopharyngeal nerve
 Vagus nerve
Developmental Aspects of the Special Senses
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Formed early in embryonic development
Eyes are _____________ of the brain
All special senses are _____________ at birth
Eye problems
 _____________ —“crossed eyes” results from unequal
pulls by the external eye muscles in babies
 Ophthalmia neonatorum—conjunctivitis resulting from
mother having gonorrhea. Baby’s eyelids are swollen and
pus is produced
 _____________ —“old vision” results from decreasing
lens elasticity that accompanies aging
 Ear problems
 _____________ —type of sensorineural deafness
 _____________ —ear ossicles fuse