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Special Senses
Study Guide
Special Senses
´ Include:
´____________
´____________
´____________
´____________
´Equilibrium
´ Receptors for these senses are
located in complex sensory
organs of the head
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Olfaction
´ Impulses for smell propagate
along the ____________________to
the brain
´ Superior area of the nasal cavity
has:
´ Olfaction receptor cells in the
olfactory ____________________
Olfaction
´ _______________ hairs respond to
inhaled chemical (odorants)
´ Supporting cells:
´ Detoxify chemicals
´ Electrically insulate receptors
´ Provide support and nourishment
´ ____________ cells: continually
divide to produce new olfactory
receptor cells
´ Olfactory glands: produce mucus
to dissolve odorants
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How smell works:
´ Olfactory receptor cells are excited by
________________ molecules
´ Results in production of a generator
potential, which might result in an
action potential
´ Bundles of axons of olfactory receptor
cells form the left and right olfactory
nerves
´ Olfactory nerves convey impulses of
smells to the olfactory bulb, olfactory
tracts, limbic system, and cerebral
cortex
´ Olfaction has a __________threshold:
only a __________molecules are
needed to be perceived as an odor.
´ Adaptation to odors occurs rapidly.
Gustation
´ Distinguishing five tastes:
´ Bitter
´ _____________
´ Sweet
´ _____________
´ Umami
´ Taste buds: have receptors for taste.
´ ______________: increase friction with
food to help manipulate it. Taste buds
are found in the following papillae:
´ Vallate
´ Fungiform
´ Foliate
´ Filiform
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Taste Buds
´ Each __________________ consists of:
´ Supporting cells
´ Basal cells
´ Gustatory receptor cells
´ Gustatory receptor cells have:
´ Gustatory _______________ projecting
through a gustatory pore to the surface
How taste works
´ Tastants: dissolve in saliva, bind to
gustatory hairs, stimulate receptor
cells, action potential can be
generated
´ 3 cranial nerves propagate
gustation impulses to ____________.
________________
´ Some are projected on to limbic
system, hypothalamus, thalamus,
cerebral cortex
´ Threshold for each of the primary
tastes varies
´ Adaptation to taste occurs
______________
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Vision
´ Protected by:
´ _________________
´ Shade, protect eye
´ Spread lubricants over eyeballs
´ __________________
´ Protect eyeballs
´ __________________
´ Protect eyeballs
´ Lacrimal _________________
´ Contain structures that produce and
drain lacrimal fluid
´ Tears protect, clean, and lubricate the
eyeball
´ Six muscles move each eyeball
´ Wall of eyeball has three layers: Structure of The Eye
1. ______________ tunic
´ Consists of white sclera
´ Tough, protective
2. ______________ tunic
´ Between fibrous tunic and retina
´ Choroid: supplies nutrients to the retina
´ Ciliary body: secretes aqueous humor and controls
shape of the lens
´ Iris: regulates the diameter of the central opening, the
pupil
3. Retina
´ Innermost tunic
´ Pigmented layer: prevents scattering of light rays
´ Neural layer: has bipolar cells, ganglion cells, and
photoreceptors
´ Rods: photoreceptors stimulated by low light and allow
night or dim vision
´ Cones: photoreceptors that are stimulated by bright
light and produce color vision
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Transmission of
Visual Information
´ Visual info is passed from photoreceptors
à bipolar cells à ganglion cells
´ Axons of ganglion cells extend to the
optic disc
´ Also known a the ‘________ _________’ as it
has no rods or cones
´ Exit the eyeball as the _______________
´ _________ _____________: portion of retina
that contains only cones
´ Area of highest visual acuity
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Lens
´ Posterior to the pupil and iris
´ Functions to focus images on the retina
´ Light rays enter the eye and undergo
_____________________
´ Light rays are bent at each surface of the
cornea and the lens
´ Focuses an inverted image on the fovea
centralis of the retina
´ Anterior and posterior lens surfaces are
_______________
´ Increasing the lens curvature increases its
focusing power
´ Accommodation: increase in the
curvature of the lens for near vision
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Image Formation
´ _________________ eye: normal eye
´ Refracts light rays so that a clear image is
focused on the retina
´ _______________: nearsightedness
´ Inability to focus properly on distant objects
´ _______________: farsightedness
´ Inability to focus on nearby objects
´ Astigmatism
´ Irregular curvature to the cornea or lens that
causes parts of an image to be out of focus or
distorted
´ Constriction of the pupil: autonomic reflex
that prevents light rays from entering at the
periphery of the lens, causes blurred vision
´ _____________ vision: allows depth perception
´ Convergence: eyes moving medially when
objects move closer so that light rays from
the object can strike the same points on both
eyes
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Neural pathway of light
´ Photoreceptors àbipolar cells àganglion cells àoptic nerve àprimary
visual cortex
´ Photoreceptors have ___________________ that transduce light energy into a
receptor potential
´ Rods have photopigment rhodopsin
´ Cones have 3 different cone photopigments that absorb different colors of light
´ __________ adaptation: when photoreceptors adjust to a brighter
environment
´ Decreases their sensitivity
´ __________ adaptation: when photoreceptors increase sensitivity
´ Only rods function at low light intensity
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Neural pathway of light
´ Light strikes the retina, leads to receptor
potential in photoreceptors, then
receptor potential in bipolar cells.
´ Bipolar cells transmit receptor potentials
to ganglion cells, which generate
action potentials
´ Ganglion cell axons exit the eye as the
________ __________
´ Optic nerve axons pass through optic
chiasm, forming the optic tract
´ Optic radiations allow for projection to
the primary visual areas of cerebral
cortex
´ _________ __________: everything that
can be seen by one eye
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Hearing
´ Ear is divided into three regions:
1. External
´ 3 Structures
´ ______________: collects sound
waves
´ External auditory canal: carries
sound waves from auricle to
tympanic membrane
´ ____________ membrane:
separates the external auditory
canal from the middle ear
2. Middle
´ Auditory ossicles, oval window,
round window, auditory tube
3. Internal
´ Bony labyrinth
´ Membranous labyrinth
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Internal Ear
´ Consists of:
1. Bony labyrinth
´ Semicircular __________ and vestibule
´ Receptors for equilibrium
´ Transmit impulses to the vestibular
branch of the vestibulocochlear nerve
´ __________________
´ Receptors for hearing
´ Spiral organ contains _______ ________
(receptors for hearing)
´ Hair cells synapse with cochlear
branch of vestibulocochlear nerve
2. Membranous labyrinth
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1. Auricle directs sound waves into
external auditory canal Pathway of Sound
2. Sound waves strike tympanic
membrane, which vibrates
3. Vibrations are transmitted through
auditory ___________ (malleus, incus,
stapes)
4. Vibrations are transmitted to oval
window
5. Fluid pressure waves created in
_______________
6. Pressures waves transmitted around
cochlea until reaches round window
7. Pressure waves travel into the
cochlear duct
8. Pressure waves move hair cells of
spiral organ, produces receptor
potentials that ultimately lead to
impulses
9. Sound waves of different frequencies
cause different regions of the basilar
membrane to ____________ at
different intensities
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Auditory Signals to the Brain
1. Hair cells bend, mechanical vibrations
are converted to receptor potentials
2. Initiate impulses in sensory neurons in
cochlear branch of vestibulocochlear
nerve
3. Cochlear branch neurons terminate in
_____________ _______________
4. Auditory signals travel to thalamus,
then primary auditory area in cerebral
cortex
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Static Equilibrium
´ Static equilibrium:
´ Orientation of the body relative to the pull of
________________
´ Sense organs for static equilibrium:
´ __________________
´ Contain hair cells, act as receptors
´ Have otoliths, amplify the pull of gravity during
movements
´ Movements that stimulate receptors for
static equilibrium
´ Tilting ____________ forward/backward
´ Linear acceleration or deceleration
´ Vestibular _________________: receptor organ
for equilibrium
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Dynamic Equilibrium
´ Dynamic equilibrium:
´ Maintaining body position in response to
___________________movements
´ Main sense organs of dynamic equilibrium:
´ _______________ in three semicircular ducts
´ Contain hair cells, which result in impulses in the vestibular
branch of vestibulocochlear nerve when bent
´ Vestibular branch axons terminate in ____________
_______________ and pons
´ Some terminate in cerebellum
´ Cerebellum:
´ Receives sensory information from all structures of the
vestibular apparatus
´ Important for maintaining BOTH static and dynamic
equilibrium
´ Makes corrective adjustments to skeletal muscle movements
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