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Name the 5 special senses
- 1. Smell
- 2. Taste
- 3. Vision
- 4. Hearing
- 5. Equilibrium
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Where are the special senses housed?
Complex sensory organs
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What are the chemical receptors?
- 1. Olfaction (smell) and
- 2. Gustation (taste)
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What covers the superior nasal cavity and cribriform plate?
Olfactory Epithelium
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How many types of receptor cells in the olfactory epithelium?
3
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Olfacttion:
Bipolar neurons with cilia or olfactory hairs
Olfactory receptors
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Olfaction:
Supporting cells
Columnar epithelium
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Olfaction:
Basal cells =
Stem cells
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Olfaction:
What replaces receptors monthly?
Basal cells aka stem cells
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Olfactory glands
Bowman's glands
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Form the olfactory nerves (Cranial nerve I) that synapse in the olfactory bulb
Axons from the olfactory receptors
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What passes through foramina in cribriform plate?
Axons from olfactory receptors
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Form the olfactory tract that synapses on cortical areas of the Limbic system
Second-order neurons within the olfactory bulb
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Emotional responses and memory processing
Second-order neurons within the olfactory bulb
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Some olfactory pathways lead to the __________where identification of odor occurs
thalamus
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What does taste require?
Dissolving of substances
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What are the five classes of stimuli?
- 1. sour
- 2. bitter
- 3. sweet
- 4. salty
- 5. umani (meaty or savory)
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Where are taste buds found?
- Tongue
- Soft palate
- Epiglottis
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Found on sides of vallate, foliate & fungiform papillae (not on filiform papillae)
Taste buds
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What are the 3 types of taste? (cells)
- Supporting cells
- Receptor cells
- Basal cells
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An oval body consisting of 50 receptor cells surrounded by supporting cells
Taste Bud
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What projects upward through the taste pore?
A single gustatory hair
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Basal cells develop into new receptor cells every ____days
10
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Physiology of Taste:
Complete adaptation occurs in ____________
1 to 5 minutes
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Thresholds for tastes vary among _____________________
the 5 primary tastes
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Thresholds for taste:
Most sensitive to bitter
poisons
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Thresholds for taste:
Least sensitive to ______ and _______
salty and sweet
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Taste Mechanism:
Dissolved substance contacts __________ _______
gustatory hairs
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Taste Mechanism:
Where is the nerve impulse formed?
1st order neuron
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Where are first-order gustatory fibers found?
In cranial nerves
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Serves anterior 2/3 of tongue
CN VII (facial)
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Serves posterior 1/3 of tongue
CN IX (glossopharyngeal)
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Serves palate & epiglottis
CN X (vagus)
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Gustatory Pathway:
Signals travel to brain stem and thalamus or __________ & ___________
limbic system & hypothalamus
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Extend from the thalamus to the primary gustatory area on parietal lobe of the cerebral cortex
Taste fibers
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Provide conscious perception of taste
Taste fibers extend from the thalamus to the primary gustatory area on parietal lobe of the cerebral cortex
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What are the 3 accessory structures of the eye?
- 1. eyelids
- 2. eyelashes and eyebrows
- 3. lacrimal glands
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Help protect eye from foreign objects, perspiration and sunlight
Eyelashes & Eyebrows
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Found at base of eyelashes (sty)
Sebaceous glands
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Gap between the eyelids
Palpebral fissure
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Lacrimal Apparatus:
How much tears are produced per day? And what is it used for?
1 ml; spread over eye by blinking
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Contains bactericidal enzyme called lysozyme
tears
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What are the 3 Tunics (Layers) of eyeball
- 1. Fibrous Tunic (outer layer)
- 2. Vascular Tunic (middle layer)
- 3. Nervous Tunic (inner layer)
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Fibrous Tunic
Nonvascular, Transparent
Helps focus light (refraction)
Parallel collagen fibers
Cornea
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Why are cornea transplants common and successful?
no blood vessels so no antibodies to cause rejection
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How is the cornea nourished?
By tears & aqueous humor
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“White” of the eye
Dense irregular connective tissue layer -- collagen & fibroblasts
Provides shape & support
Sclera (Fibrous Tunic)
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At the junction of the sclera and cornea is an ______(scleral venous sinus)
opening
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Sclera posteriorly pierced by _____________
Optic Nerve (CNII)
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Vascular Tunic
Pigmented epithilial cells (melanocytes) & blood vessels
Provides nutrients to retina
Black pigment in melanocytes absorb scattered ligh
Choroid
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Folds on ciliary body
Secrete aqueous humor
Ciliary Processes
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Smooth muscle that alters shape of lens
Ciliary Muscle
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What are the two parts of the ciliary body?
Ciliary processes & Ciliary muscle
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Suspensory ligaments attach lens to _______ _______
Ciliary process
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Vascular Tunic - Ciliary Body
Controls tension on ligaments & lens
Ciliary muscle
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Vascular Tunic
Colored portion of eye
Shape of flat donut suspended between cornea & lens
Hole in center is pupil
Function is to regulate amount of light entering eye
Iris
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Vascular Tunic
Constrictor pupillae (circular) are innervated by parasympathetic fibers while Dilator pupillae (radial) are innervated by sympathetic fibers.
Response varies with different levels of light
Muscles of the Iris
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Avascular
Crystallin proteins arranged like layers in onion
Clear capsule & perfectly transparent
Lens
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Held in place by suspensory ligaments
Lens
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Focuses light on retina
Lens
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Nervous Tunic
Posterior 3/4 of eyeball
Macula lutea with central fovea
Optic disc
Retina
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Optic nerve exiting back of eyeball
Optic disc
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Layers of Retina:
Nonvisual portion
Absorbs stray light & helps keep image clear
Pigmented Layer
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Neural layer:
What are the 3 layers of neurons (outgrowth of brain)
- 1. photoreceptor layer
- 2. bipolar neuron layer
- 3. ganglion neuron laye
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Discriminates shapes & movements
Shades of gray in dim light
Distributed along periphery
Rods --- rod shaped
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How many rod cells are there?
120 million rod cells
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Sharp, color vision
6 million
Fovea of macula lutea
Cones
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Densely packed region
At exact visual axis of eye
Sharpest resolution or acuity
Fovea of macula lutea
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Cavities of the Interior of Eyeball:
Filled with aqueous humor
Produced by ciliary body
Continually drained
Anterior cavity (anterior to lens)
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Where is the anterior chamber of the eyeball?
Between cornea and iris
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Where is the posterior chamber of the eyeball?
Between iris and lens
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Cavities of the Interior of Eyeball:
Filled with vitreous body (jellylike)
Formed once during embryonic life
Floaters are debris in vitreous of older individuals
Posterior cavity (posterior to lens)
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Continuously produced by ciliary body
Flows from posterior chamberinto anterior through the pupil
Aqueous Humor
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Canal of Schlemm
Opening in white of eyeat junction of cornea & sclera Drainage of aqueous humor from eye to bloodstream
Scleral venous sinus
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Increased intraocular pressure that could produce blindness
Problem with drainage of aqueous humor
Glaucoma
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Collect sounds
External Ear
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Elastic cartilage covered with skin
auricle or pinna
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ceruminous glands produce cerumen
Ear wax
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Curved tube of cartilage & bone leading into temporal bone
External auditory canal
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tympanic membrane
eardrum
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What is the tympanic membrane made of?
epidermis, collagen & elastic fiber
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Air filled cavity in the temporal bone
Separated from external ear by eardrum and from internal ear by oval & round window
Middle Ear Cavity
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3 ear ossicles connected by ________ ______
synovial joints
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Auditory tube leads to ____________
nasopharynx
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helps to equalize pressure on both sides of eardrum
nasopharynx
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Middle Ear Cavity:
malleus attached to eardrum, incus & stapes attached by foot plate to membrane of _____ ________
oval window
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Stapedius muscle inserts onto ____
stapes
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Muscles of the ear:
prevents very large vibrations of stapes from loud noise
Stapedius muscle
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Tensor tympani attaches to _______
malleus
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Limits movements of malleus & stiffens eardrum to prevent damage
Tensor tympani
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Inner Ear
Set of tubelike cavities in temporal bone
Bony labyrinth
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Inner Ear:
semicircular canals, vestibule & cochlea lined with periosteum & filled with __________
perilymph
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Inner Ear:
Surrounds & protects Membranous Labyrinth
Bony labyrinth
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Inner Ear:
Set of membranous tubes
Membranous labyrinth
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Inner Ear:
Containing sensory receptors for hearing & balance and filled with endolymph
membranous labyrinth
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What are the 3 fluid filled channels found within the cochlea?
- 1. scala vestibuli
- 2. scala tympani
- 3. cochlear duct
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Section thru one turn of Cochlea:
Partitions that separate the channels are ____ shaped
Y shaped
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Section thru one turn of Cochlea:
Vestibular membrane above & basilar membrane below form the _____________________
Central fluid filled chamber (cochlear duct)
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Section thru one turn of Cochlea:
Receptor cells located in ________________
spiral organ of Corti
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Section thru one turn of Cochlea:
Hair endings on cells insert into ______________
tectorial membrane
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Anatomy of the Organ of Corti:
hair cells have _______________
Stereocilia (microvilli)
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Anatomy of the Organ of Corti:
Make contact with tectorial membrane (gelatinous membrane that overlaps the spiral organ of Corti)
Microvilli
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Mechanism of hearing:
Pushes on fluid of scala vestibuli at oval window
Stapes
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Mechanism of hearing:
Where does the vibration move into scala tympani?
At helicotrema
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Mechanism of hearing:
Dissipated at round window which bulge
Fluid vibration
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Mechanism of hearing:
The central structure is vibrated aka
cochlear duct
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Sounds at different frequencies vibrate different portions of the _____ ________
Basilar membrane
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Vibrate the stiffer more basal portion of the cochlea
high pitched sounds
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Vibrate the upper cochlea whichis wider and more flexible
Low pitched sounds
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Cause a greater vibration of the basilar membrane & stimulate more hair cells which our brain interprets as “louder”
Loud sounds
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Vestibulocochlear nerve (CN VIII)
Carries sensory inputs for hearing into brain stem and then projects to inferior colliculus, thalamus (medial geniculate nucleus) and primary auditory cortex
Cochlear part of cranial nerve
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Semicircular ducts with ampulla, utricle & saccule
Vestibular Apparatus
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Maintain the position of the body (head) relative to the force of gravity
Macula receptors within saccule & utricle
Static equilibrium
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Otolithic Organs: Saccule & Utricle
Thickened regions within the saccule & utricle of the vestibular apparatus
Macula
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Otolithic Organs: Saccule & Utricle--
Gelatinous otolithic membrane contains calcium carbonate crystals called ___________
otoliths
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Move when you tip your head
Otoliths
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Detection from: Movement of stereocilia or kinocilium results in the release of neurotransmitter onto the vestibular branches of the vestibulocochler nerve
Detection of Position of Head
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Maintain body position (head) during sudden movement of any type--rotation, deceleration or acceleration
Crista receptors within ampulla of semicircular duct
Dynamic equilibrium
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Detection of Rotational Movement:
When the head moves, what moves with it?
The attached semicircular ducts and hair cells
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Detection of Rotational Movement:
When the head moves this does not, and bends the cupula and enclosed hair cell
Endolymph fluid
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Detection of Rotational Movement:
What region: ampulla, membrane called crista
Receptor region
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Cranial nerves of the Ear Region:
Vestibulocochelar nerve
CN VIII
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Cranial nerves of the Ear Region:
Form the vestibular branch
- Branches:
- 1. Ampullary
- 2. Utricular
- 3. Saccular
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Cranial nerves of the Ear Region:
Has spiral ganglion in bony modiolus
Cochlear branch
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Vestibulocochlear nerve (CN VIII):
Carries sensory inputs for equilibrium into brain stem and then projects to cerebellum, cerebral cortex and spinal cord
Vestibular part of cranial nerve
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