A&P
Chapter 16 Quiz Topics – Special Senses
o
Chemical Senses
 Olfaction/Smell
 Olfaction receptors are located in the olfactory epithelium of the nasal cavity
 Enhance taste
 Link to limbic system & correlation with memories/emotion
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o
Gustation/Taste
 Gustatory cells are located in the taste buds
 Papillae
 Each taste specialization response to a specific chemical
o Sweet (OH-), sour (H+), bitter (alkaloids) & salty (metal ions)
o Temperature & texture influence taste
o “hot”/spicy excites pain receptors
Substances must be in solution to stimulate olfactory cells and taste buds
Vision
 70% of all sensory cells are located in the eye
 Major structures of the eye
-The Tunics

The Fibrous Tunic
o Cornea – transparent tissue covering the front of the eye: does not have blood
vessels; does have nerves; can be transplanted without rejection b/c avascular
o Sclera - tough, white outermost protective covering of the eyeball; extraocular
muscles attach here to move the eye

The Vascular (blood tunic)
o Choroid – Thin tissue layer containing blood vessels, sandwiched between the
sclera and retina; also, because of the high melanocytes content, the choroid acts as
a light-absorbing layer.
o Ciliary body (muscles) – involuntary muscles that change the lens shape to allow
focusing images of objects at different distances
o Iris – circular band of muscles that controls the size of the pupil. The pigmentation
of the iris gives "color" to the eye. Blue eyes have the least amount of pigment;
brown eyes have the most
o Pupil – hole in the center of the eye where light passes through

The Sensory Tunic
o Retina – layer of tissue on the back portion of the eye that contains cells responsive
to light (photoreceptors); the retina consists of a pigmented and neural layer
o Pigmented layer: the pigmented cell layer just outside the neurosensory retina that
nourishes retinal visual cells, and is firmly attached to the underlying choroid and
overlying retinal visual cell
o Neural Layer: neurosensory layer that contains photoreceptor neurons, bipolar
cells and ganglion cells.
o Optic nerve (disk) – bundle of over one million axons from ganglion cells that carry
visual signals from the eye to the brain; glaucoma results from damage to optic
nerve causing fluid blockage
o Blind spot - small area of the retina where the optic nerve leaves the eye: any image
falling here will not be seen
o Cones – photoreceptors responsive to color and in bright conditions; used for fine
detail
o Rods – photoreceptors responsive in low light conditions; not useful for fine detail
o Macula – small central yellow pigmented area of the retina; provides vision for fine
work and reading; yellow pigmented area
Fovea centralis– central part of the macula that provides sharpest vision; contains
only cones
-Internal Chambers and Fluids:
 Aqueous humor - clear watery fluid found in the anterior chamber of the eye; maintains
pressure and nourishes the cornea and lens
 Vitreous humor - clear, jelly-like fluid found in the back portion of the eye: maintains shape
of the eye and attaches to the retina to hold it against surrounding tunics
-The Lens:
 transparent tissue that bends light passing through the eye: to focus light, the lens can
change shape
 Lens flattens for distance vision and bulges for close vision
 Emmetropic eye: regular vision: light from both near and far objects is focused properly on
the retina
 Myopic eye: nearsightedness (can see close objects w/o problem): lens from a distant object
is brought to a focal point before reaching the retina and then diverges again
 Hyperopic eye: farsightedness (can see distant objects without problem) – light from a near
object is brought to a focal point past the retina.
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Visual Pathway:
 Light passes through cornea, aqueous humor, lens, vitreous humor prior to reaching the
retina
 Pathway to the brain begins in the retina where light activates photoreceptors.
 Photoreceptors signal bipolar cells, which signal ganglion cells.
 Axons of ganglion cells exit eye as the optic nerve
 Most visual information travels to the occipital lobe of the cerebral cortex responsible for
conscious “seeing”
 Other pathways travel to nuclei in the midbrain and diencephalon
o
Hearing & Balance
 Major structures of the ear

External Ear
o Auricle/Pinna – what you call the ear; shell-shaped projection of elastic cartilage
that helps direct sound waves to the auditory canal
o External acoustic meatus/canal – short curved tube that extends from the auricle
to the ear drum; lines with ceruminous glands that secrete earwax to trap foreign
substances and repel insects
o Tympanic Membrane – the eardrum; boundary between outer and middle ears;
thin, translucent connective tissue membrane vibrates in response to sound waves
and transmits the vibrations to the ossicles of the middle ear

Middle Ear
o Oval window – one of two membrane-covered openings of the middle ear; leads
from the middle ear to the vestibule of the inner ear, the intersection of the middle
ear with the inner ear; by the time vibrations reach the oval window, they have been
amplified over twenty times from what they were when they contacted the
tympanic membrane
o Round window – second opening of the middle ear; the round window membrane
vibrates opposite vibrations entering the inner ear through the oval window; it
allows fluid in the cochlea to move, which in turn ensures that hair cells of the
basilar membrane will be stimulated and that audition will occur.
o
o
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Auditory/Pharyngotympanic tube – connects the middle ear and pharynx; also
called the Eustachian tube
Ossicles – three small bones (smallest bones in the body) that transmit vibratory
motion of the eardrum to the oval window which sets the fluids of the inner ear in
motion, exciting the hearing receptors
 Mallues (hammer)– first bone in sequence, “handle” is secured to the ear
drum
 Incus (anvil) – connects malleus to stapes
 Stapes (stirrup) – base fits into the open window
Internal Ear (labyrinth)
o Bony labyrinth – system of channels worming through the cranial (temporal) bone
o Membranous labyrinth – series of membrane sacs and ducts within the bony
labyrinth
o Vestibule – central egg-shaped cavity of the bony labyrinth
o Semicircular Canals – lie posterior and lateral to the vestibule; Each canal is filled
with a fluid called endolymph that contains motion sensors; receptors respond to
angular (rotational) movements of the head
o Cochlea – snail shaped chamber of the bony labyrinth that houses the receptor for
hearing
o Spiral Organ of Corti – contains hearing receptor cells, “hair cells” that transform
sound waves to action potentials
When visual and vestibular inputs do not match, motion sickness may result

Account for Sensory Phenomena (Be able to account for THREE in lieu of “At the Clinic” which we did not do for this
unit)
o Chemoreceptors
 Interdependence of Taste & Smell
 Importance of Smell
 Tongue map
o Thermoperceptors
 Relative density of hot v. cold receptors
 Response is relative
o Photoreceptors & visual perception
 The Blind Spot
 After images
 Ocular dominance
 Depth perception
 Cues we rely on for depth perception
 Snellen visual acuity test
 Astigmatism
 Accommodation of light intensity
o Hearing & Balance
 Nerve deafness vs. conduction deafness