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- Oregon
- Portland Community College
- Biology
- Biology 232
- Salti
- Ch16 special senses
Ch16 special senses
Biology 232 with Salti at Portland Community College
About this deck
By: Amanda Duncan
Created: 2012-04-30
Size: 143 flashcards
Views: 17
Created: 2012-04-30
Size: 143 flashcards
Views: 17
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chemical senses are...
– Gustation (taste)
– Olfaction (smell)
– Olfaction (smell)
chemoreceptors
– Respond to chemicals in aqueous solution
– Taste: substances dissolved in saliva
– Smell: substances dissolved in fluids of the nasal membranes
– Taste: substances dissolved in saliva
– Smell: substances dissolved in fluids of the nasal membranes
taste buds
• Taste receptors found on the tongue (mainly), inside the cheeks, soft palate, pharynx, epiglottis.
• Taste buds contain taste receptors and specialized cells
• Adults have about 4000 taste buds
• Taste buds contain taste receptors and specialized cells
• Adults have about 4000 taste buds
lingual papillae
four types of protrusions distributed on the superior surface of the tongue
filliform papillae
– most abundant
– do not contain taste buds
– provide friction that helps the tongue to move objects around the mouth
– Senses food texture.
– do not contain taste buds
– provide friction that helps the tongue to move objects around the mouth
– Senses food texture.
fungiform papillae
– shaped like a mushroom
– widely distributed, but mostly concentrated at the tip and sides of the tongue.
– Each has about 3-5 taste buds located mainly on the apex.
– widely distributed, but mostly concentrated at the tip and sides of the tongue.
– Each has about 3-5 taste buds located mainly on the apex.
circumvallate papillae
– 7-12 large papillae
– form a V at the rear of the tongue.
– Each is surrounded by a deep circular trench.
– Each has a bout 100-250 taste buds located on the wall of the papilla facing the trench.
– form a V at the rear of the tongue.
– Each is surrounded by a deep circular trench.
– Each has a bout 100-250 taste buds located on the wall of the papilla facing the trench.
foliate papillae
– weakly developed in humans.
– parallel ridges on the sides of the tongue next to the molar and premolar teeth.
– Most of their taste buds degenerate by the age of 2 or 3 years.
– parallel ridges on the sides of the tongue next to the molar and premolar teeth.
– Most of their taste buds degenerate by the age of 2 or 3 years.
anatomy of the taste bud
• All taste buds look alike; no difference in structure.
• They are lemon-shaped.
• Have 50 to 150 taste cells, supporting cells, and basal cells.
• Taste receptors adapt slowly, but central adaptation occur quickly
• They are lemon-shaped.
• Have 50 to 150 taste cells, supporting cells, and basal cells.
• Taste receptors adapt slowly, but central adaptation occur quickly
taste buds: taste cells
– banana-shaped epithelial cells (not neurons) serve as taste receptor.
– They live 7 to 10 days.
– have a tuft of microvilli (hairs) that project into a taste pore on the epithelial surface of the tongue
– They synapse with sensory nerve at their base and
– have synaptic vesicles for the release of neurotransmitters.
– They live 7 to 10 days.
– have a tuft of microvilli (hairs) that project into a taste pore on the epithelial surface of the tongue
– They synapse with sensory nerve at their base and
– have synaptic vesicles for the release of neurotransmitters.
taste buds: supporting cells
– resemble taste cells but have no synaptic vesicles or sensory role.
– insulate the receptor
– insulate the receptor
taste buds: basal cells
– stem cells that multiply to replace dead taste cells
– Synapse with sensory nerve of the taste bud and may play some role in processing of sensory information before the signal goes to the brain.
– Synapse with sensory nerve of the taste bud and may play some role in processing of sensory information before the signal goes to the brain.
taste sensations: sweet
sugars, saccharin, alcohol, and some amino acids
taste sensations: bitter
associated with spoiled foods and alkaloids such as nicotine, caffeine, quinine, and morphine.
– Alkaloids are often poisonous, and the bitter taste induces a animals to reject a food.
– plant leaves are bitter to deter animals from eating them.
– Causes increase intracellular Ca levels.
– Alkaloids are often poisonous, and the bitter taste induces a animals to reject a food.
– plant leaves are bitter to deter animals from eating them.
– Causes increase intracellular Ca levels.
taste sensations: sour
associated with acids (H+) in such foods as citrus fruits
taste sensations: salty
produced by metal ions such as sodium and potassium
taste sensations: umami
Pronounced “ooh-mommy,” Japanese slang for “yummy.”
– produced by amino acids such as aspartic and glutamic acids
– Responsible for meat taste and MSG.
– Taste buds present in the circumvallate papillae
– produced by amino acids such as aspartic and glutamic acids
– Responsible for meat taste and MSG.
– Taste buds present in the circumvallate papillae
taste sensations: water receptors
especially in pharynx, carry impulses to hypothalamus
taste sensations: Phenylthiourea:
is inherited; some can't taste it
sensitivity to taste is greatest where in the tongue?
– The tip of the tongue is most sensitive to sweet tastes and sweet and salty are the least sensitive.
– The lateral margins of the tongue are the most sensitive areas for salty and sour tastes.
– Taste buds in vallate papillae are sensitive to bitter compounds
– sense of alkaloid is the most sensitive; we can taste lower concentrations of alkaloids than of acids, salts, and sugars.
– The lateral margins of the tongue are the most sensitive areas for salty and sour tastes.
– Taste buds in vallate papillae are sensitive to bitter compounds
– sense of alkaloid is the most sensitive; we can taste lower concentrations of alkaloids than of acids, salts, and sugars.
influences of other sensations on taste
– texture, temperature, appearance, and one's state of mind, among other things.
– sensations such as texture and temperature are carried by trigeminal nerve (V); lingual branch.
– Taste is 80% smell (aroma)
• cinnamon merely has a faintly sweet taste
• coffee and peppermint are bitter
• apples and onions taste almost identical
– sensations such as texture and temperature are carried by trigeminal nerve (V); lingual branch.
– Taste is 80% smell (aroma)
• cinnamon merely has a faintly sweet taste
• coffee and peppermint are bitter
• apples and onions taste almost identical
physiology of taste
• Dissolved chemicals bind to receptor and depolarize taste cell membrane
• Sodium and acids penetrate into the cell and depolarize it directly.Sweet (Sugars), bitter (alkaloids), Umami (glutamate) stimulate taste cells by binding to receptors on the membrane surface, which then activate G proteins and second-messenger systems within the cell; (gustducins)
• Taste cells then release neurotransmitters that stimulate the sensory dendrites at their base.
• Sodium and acids penetrate into the cell and depolarize it directly.Sweet (Sugars), bitter (alkaloids), Umami (glutamate) stimulate taste cells by binding to receptors on the membrane surface, which then activate G proteins and second-messenger systems within the cell; (gustducins)
• Taste cells then release neurotransmitters that stimulate the sensory dendrites at their base.
how does age affect one's ability to taste?
– Taste buds decline in numbers and sensitivity
gustatory pathway and cranial nerves
• facial nerve VII: carry taste sensations information from anterior two-thirds of the tongue.
• glossopharyngeal IX nerve: carry taste sensation from posterior third of the tongue.
• vagus X nerve: carry taste sensation from palate, pharynx, and epiglottis.
• glossopharyngeal IX nerve: carry taste sensation from posterior third of the tongue.
• vagus X nerve: carry taste sensation from palate, pharynx, and epiglottis.
gustatory pathways: after the cranial nerves
• Information carried by cranial nerves to solitary nucleus in medulla. impulses then travel to medial lemniscus and join axons carrying somatic, touch, pressure, and proprioception information.
• Solitary nucleus relay signals to nuclei in hypothalamus and amygdala (to activate autonomic reflexes such as salivation, gagging, and vomiting) and to thalamus, which then relays signals to insula and postcentral gyrus of cerebrum, where we become conscious of the taste.
• Solitary nucleus relay signals to nuclei in hypothalamus and amygdala (to activate autonomic reflexes such as salivation, gagging, and vomiting) and to thalamus, which then relays signals to insula and postcentral gyrus of cerebrum, where we become conscious of the taste.
processed impulses from the gustatory pathway go where?
Processed signals are further relayed to the orbitofrontal cortex, to integrated with signals from nose and eyes and we form an overall impression of the flavor and palatability of food.
olfactory organ
– Paired, located in the nasal cavity on either side of the nasal septum
– responsible for smell sensation or olfaction
• The number of receptors and sensitivity decline with aging
– responsible for smell sensation or olfaction
• The number of receptors and sensitivity decline with aging
olfactory organ consists of two layers
• olfactory epithelium
• Underlying lamina propria
• Underlying lamina propria
olfactory organ: olfactory epithelium
– covers the inferior surface of the cribriform plate, superior portion of the ethmoid perpendicular plate, and the superior nasal conchae
– contains:
Olfactory receptor cells:
» supporting cells
» Basal cells
– contains:
Olfactory receptor cells:
» supporting cells
» Basal cells
olfactory epithelium: olfactory receptor cells
a bipolar neurons with radiating olfactory cilia, stimulated by water and lipid soluble substances
that diffuse into the overlying mucus
that diffuse into the overlying mucus
olfactory epithelium: supporting cell
surround olfactory receptors
olfactory epithelium: basal cells
lie at the base of the epithelium. New receptors produced by the division and differentiation of the basal cells
olfactory organ: underlying lamina propria
– consist of areolar connective tissue, blood vessels, nerves, and bowman’s glands or olfactory gland whose secretions absorb water and form a thick pigmented mucus
olfactory receptors
– respond to different odors (~300)
– Very sensitive; four odorant molecules can activate olfactory receptors
– The higher solubility the stronger the smell
• When bound to ligand these proteins initiate a G protein mechanism, which uses cAMP as a second messenger
• cAMP opens Na ion channels causing depolarization of the receptor membrane that triggers an action potential
– Very sensitive; four odorant molecules can activate olfactory receptors
– The higher solubility the stronger the smell
• When bound to ligand these proteins initiate a G protein mechanism, which uses cAMP as a second messenger
• cAMP opens Na ion channels causing depolarization of the receptor membrane that triggers an action potential
olfactory pathway
• 20 or more axons leaving the olfactory epithelium, bundle and penetrate cribriform plate to synapse at olfactory bulb
• Axons from olfactory bulb travel along olfactory tract to reach olfactory cortex, hypothalamus, and the limbic system which explains the emotional and behavioral responses, and memories associated with a smell
• Axons from olfactory bulb travel along olfactory tract to reach olfactory cortex, hypothalamus, and the limbic system which explains the emotional and behavioral responses, and memories associated with a smell
olfactory receptor adaptation
• The adaptation is central; olfactory receptors have little adaptation:
– Efferent fibers from elsewhere in the brain innervate olfactory bulbs. This provide central adaptation or facilitation
– Efferent fibers from elsewhere in the brain innervate olfactory bulbs. This provide central adaptation or facilitation
basic anatomy of the ear
– parts of the ear are the inner, outer, and middle ear
• The outer and middle ear are for hearing
• The inner ear for hearing and equilibrium
• The outer and middle ear are for hearing
• The inner ear for hearing and equilibrium
receptors for hearing and balance
– Respond to separate stimuli
– Are activated independently
– Are activated independently
external ear: auricle
– Surrounds the external acoustic canal
– Collects and directs sounds to the middle ear
– composed of helix (rim), lobule (earlobe)
– Collects and directs sounds to the middle ear
– composed of helix (rim), lobule (earlobe)
external ear: external auditory canal
– Short, curved tube, ends at the tympanic membrane
– contains ceruminous glands that secret cerumen which slows microorganism growth and denies access to insects and foreign objects
– The hairs provide tactile sensitivity through hair plexuses
– contains ceruminous glands that secret cerumen which slows microorganism growth and denies access to insects and foreign objects
– The hairs provide tactile sensitivity through hair plexuses
external ear: tympanic membrane
– Thin semitransparent connective tissue membrane.
– Separates between outer and middle ears
– Vibrates and transfers sound energy to the middle ear ossicles
– Separates between outer and middle ears
– Vibrates and transfers sound energy to the middle ear ossicles
middle ear
• A small, air-filled, mucosa-lined cavity located in the petrous region of the temporal bone.
• Contains auditory ossicles; malleus, incus, and stapes
• Flanked laterally by the eardrum and medially by the oval and round windows
• Contains auditory ossicles; malleus, incus, and stapes
• Flanked laterally by the eardrum and medially by the oval and round windows
middle ear: epitympanic recess
the superior portion of the middle ear
middle ear: pharyngotympanic tube
– Connects the middle ear to the nasopharynx
– Equalizes pressure in the middle ear cavity with the external air pressure
– The portion near the middle ear is narrow and supported by elastic tissue
– The portion near the nasal cavity is broad and funnel shaped
– Equalizes pressure in the middle ear cavity with the external air pressure
– The portion near the middle ear is narrow and supported by elastic tissue
– The portion near the nasal cavity is broad and funnel shaped
ossicles
• Transmit vibration of the eardrum to the oval window
• The articulations are synovial joints
• The articulations are synovial joints
ear drum dampened by two muscles
– tensor tympani: insert on the malleus, Innervated by V cranial nerve
– stapedius muscles: innervated by VII cranial nerve, insert on the stapes
– stapedius muscles: innervated by VII cranial nerve, insert on the stapes
ossicle name and position
• Malleus:
– Attaches to the interior surface of the tympanic membrane at three points
• Incus:
– Middle bone attaches malleus to stapes
• Stapes:
– Its base bind to oval window
– Attaches to the interior surface of the tympanic membrane at three points
• Incus:
– Middle bone attaches malleus to stapes
• Stapes:
– Its base bind to oval window
inner ear: bony labyrinth
– Tortuous channels in the temporal bone
– Contains vestibule, cochlea, and three semicircular canals
– Filled with perilymph
– Contains vestibule, cochlea, and three semicircular canals
– Filled with perilymph
inner ear: membranous labyrinth
– Series of membranous sacs within the bony labyrinth
– Filled with endolymph rich in potassium
– Filled with endolymph rich in potassium
inner ear: vestibule
• The central egg-shaped cavity of the bony labyrinth
• Has two sacs: the Saccule (extends into the cochlea) and utricle (extends into the semicircular canals) and are connected by a slender passageway that is continuous with the narrow endolymphatic duct that ends in a blind pouch called endolymphatic sac (projects into subarachnoid space to return excess fluid to the general circulation)
• These sacs house equilibrium receptors called maculae
• Has two sacs: the Saccule (extends into the cochlea) and utricle (extends into the semicircular canals) and are connected by a slender passageway that is continuous with the narrow endolymphatic duct that ends in a blind pouch called endolymphatic sac (projects into subarachnoid space to return excess fluid to the general circulation)
• These sacs house equilibrium receptors called maculae
inner ear: anatomy of maculae
• Hair cells processes embedded in gelatinous material that contains calcium carbonate (statoconia) on its surface, the complex is called otolith
• Distortion of processes provide sensation of gravity (head position) and linear acceleration
• Distortion of processes provide sensation of gravity (head position) and linear acceleration
inner ear: semicircular canals
• Three canals lateral, anterior, and posterior, lie in three planes of space
• Membranous semicircular ducts line each canal and communicate with the utricle
• Membranous semicircular ducts line each canal and communicate with the utricle
inner ear: semicircular canals: ampulla
is the swollen end of each canal and it houses equilibrium receptors (hairs cells) in a region called crista ampullaris
inner ear: semicircular canals: cupulla
a gelatinous structure, has a density close to the surrounding endolymph, float above the receptor surface
inner ear: semicircular canals: hair cells
– surrounded by supporting cells
– Has stereocila and one kinocilium on the free surface embedded in the cupula
– Monitored by the dendrites of sensory neurons
– Has stereocila and one kinocilium on the free surface embedded in the cupula
– Monitored by the dendrites of sensory neurons
inner ear: semicircullar canals: hair receptors respond to angular movements of the head ...
– Rotating the head in the plane of the duct, the movement of endolymph pushes the cupula and distorts the receptor processes
– Horizontal rotation stimulate the lateral duct
– Nodding stimulate anterior duct
– Tilting side to side stimulate posterior duct
• Movement of fluid in one direction stimulates the hair cells, and movement in the opposite direction inhibits them
– Horizontal rotation stimulate the lateral duct
– Nodding stimulate anterior duct
– Tilting side to side stimulate posterior duct
• Movement of fluid in one direction stimulates the hair cells, and movement in the opposite direction inhibits them
pathways for equilibrium sensation
• Sensory fibers from the vestibular ganglia form the vestibular branch of vestibulocochlear nerve (VIII) which innervate neurons within the
vestibular nuclei between the pons and medulla oblongata
• reflexive motor commands issued by the vestibular nuclei are distributed to the motor nuclei for cranial nerves involve the eye, head, and neck
movements (III, IV VI, and Xl)
vestibular nuclei between the pons and medulla oblongata
• reflexive motor commands issued by the vestibular nuclei are distributed to the motor nuclei for cranial nerves involve the eye, head, and neck
movements (III, IV VI, and Xl)
equilibrium sensation: vestibular nuclei functions
– Integrate balance sensory information that arrives from both sides
– Relay information from the vestibular complex to the cerebellum
– Relay information from the vestibular complex to the cerebral cortex, providing conscious sense of head position and movement
– Sending commands to motor nuclei in the brain stem and spinal cord
– Relay information from the vestibular complex to the cerebellum
– Relay information from the vestibular complex to the cerebral cortex, providing conscious sense of head position and movement
– Sending commands to motor nuclei in the brain stem and spinal cord
descending pathways for equilibrium adjustment
• Instructions, descending in the vestibulospinal tracts of the spinal cord, adjust peripheral muscle tone and complement the reflexive movements
of the head or neck
of the head or neck
automatic eye movements in response to sensation of motion
– are directed by the superior colliculus of the mesencephalon
– keep your gaze focused on a specific point despite changes in body position and orientation
– keep your gaze focused on a specific point despite changes in body position and orientation
inner ear: cochlea
• A spiral bony chamber that:
– Extends from the anterior vestibule
– Coils around a bony pillar called the modiolus
– Contains the cochlear duct which ends at the cochlear apex
– Extends from the anterior vestibule
– Coils around a bony pillar called the modiolus
– Contains the cochlear duct which ends at the cochlear apex
inner ear: three chambers of the cochlea
• Scala media:
– filled with endolymph and lies between scala vestibule the and scala tympani
– Contains the organ of Corti (hearing receptor)
• Scala vestibuli and scala tympani: are filled with perilymph
– scala vestibule begins at the oval window and continues with scala tympani at the tip of the spiral, which in turn terminates at the round window
– filled with endolymph and lies between scala vestibule the and scala tympani
– Contains the organ of Corti (hearing receptor)
• Scala vestibuli and scala tympani: are filled with perilymph
– scala vestibule begins at the oval window and continues with scala tympani at the tip of the spiral, which in turn terminates at the round window
inner ear: organ of Corti
• Sits on the basilar membrane that separates the cochlear from the tympanic duct
• composed of supporting cells and hair cells that have stereocilia, but lack kinocilia
• A stereocilia contact the overlying tectorial membrane which attaches firmly to the inner wall of the cochlear duct
• Afferent fibers of the cochlear nerve attach to the base of hair cells
• composed of supporting cells and hair cells that have stereocilia, but lack kinocilia
• A stereocilia contact the overlying tectorial membrane which attaches firmly to the inner wall of the cochlear duct
• Afferent fibers of the cochlear nerve attach to the base of hair cells
sound is
– A pressure disturbance (alternating areas of high and low pressure) originating from a vibrating object
– Composed of areas of rarefaction and compression
– Represented by a sine wave in wavelength, frequency, and amplitude
– Composed of areas of rarefaction and compression
– Represented by a sine wave in wavelength, frequency, and amplitude
properties of sound waves
• Frequency: the number of waves that pass a given point in a given time
• Pitch: perception of different frequencies (we hear from 20–20,000 Hz)
– High pitch sound ->High-frequency, short wavelengths and Low pitch sound->low-frequency, long wavelengths of
• Amplitude or intensity:of a sound determines how loud it seems, the larger the amplitude (Energy) the louder the sound
• Pitch: perception of different frequencies (we hear from 20–20,000 Hz)
– High pitch sound ->High-frequency, short wavelengths and Low pitch sound->low-frequency, long wavelengths of
• Amplitude or intensity:of a sound determines how loud it seems, the larger the amplitude (Energy) the louder the sound
mechanisms of hearing
• Sound waves enter the auditory canal to the eardrum and vibrations beat against the eardrum
• The eardrum pushes against the ossicles which amplify the sound
• Stapes presses fluid in the inner ear against the oval windows creating pressure waves which travel through the perilymph of the vestibular and tympanic ducts to reach the round widow
• Wave movement will distort the basilar membrane
• The eardrum pushes against the ossicles which amplify the sound
• Stapes presses fluid in the inner ear against the oval windows creating pressure waves which travel through the perilymph of the vestibular and tympanic ducts to reach the round widow
• Wave movement will distort the basilar membrane
inner ear: distortion of cochlear basilar membrane and frequency
maximum distortion varies with the frequency of the sound.
• High-frequency sounds vibrate the basilar membrane near the oval window
• Low-frequency sounds vibrate the basilar membrane farther from the oval window
• High-frequency sounds vibrate the basilar membrane near the oval window
• Low-frequency sounds vibrate the basilar membrane farther from the oval window
mechanism of hearing and vibrations of basilar membrane
• Vibration of basilar membrane moves hair cells against the tectorial membrane which lead to displacement of stereocilia
• This opens channels that depolarize the hair cells which release neurotransmitters and the stimulation of sensory neurons
• Frequency of perceived sound is determined by
– which part of the cochlear duct is stimulated
– the location of and how many hair cells are stimulated
• This opens channels that depolarize the hair cells which release neurotransmitters and the stimulation of sensory neurons
• Frequency of perceived sound is determined by
– which part of the cochlear duct is stimulated
– the location of and how many hair cells are stimulated
auditory pathway
• hair cells activate sensory neurons whose cell bodies are in the spiral ganglion
• information is carried by the cochlear branch of vestibulocochlear nerve to the ventral and dorsal cochlear nuclei in the medulla oblongata
• The information then crosses to the opposite side of the brain and ascend to the inferior colliculus
• Ascending auditory sensation synapses in the medial geniculate nucleus and then to the auditory cortex of the temporal lobe
• information is carried by the cochlear branch of vestibulocochlear nerve to the ventral and dorsal cochlear nuclei in the medulla oblongata
• The information then crosses to the opposite side of the brain and ascend to the inferior colliculus
• Ascending auditory sensation synapses in the medial geniculate nucleus and then to the auditory cortex of the temporal lobe
auditory reflexes
– involve skeletal muscles of the head, face, and trunk
– Automatically change the head position in response to noise
– Automatically change the head position in response to noise
damage to the auditory cortex and the association area
damage to the auditory cortex
– The individual will respond to sounds and have normal auditory reflexes
– The individual cannot interpret sounds and recognize a pattern in them
• Damage to adjacent association area :
– The individual can detect the tones and patterns but unable to comprehend their meaning
– The individual will respond to sounds and have normal auditory reflexes
– The individual cannot interpret sounds and recognize a pattern in them
• Damage to adjacent association area :
– The individual can detect the tones and patterns but unable to comprehend their meaning
aging and hearing
• The tympanic membrane becomes less flexible
• Articulation between ossicles stiffen
• The round window begins to ossify
• As a result, older individuals show some degree of hearing loss
• Articulation between ossicles stiffen
• The round window begins to ossify
• As a result, older individuals show some degree of hearing loss
conduction deafness
– something hampers sound conduction to the fluids of the inner ear (e.g., impacted earwax, perforated eardrum, osteosclerosis of the ossicles)
sensorineural deafness
– result from damage to the neural structures at any point from the cochlear hair cells to the auditory cortical cells
tinnitus
– ringing or clicking sound in the ears in the absence of auditory stimuli
meniere's syndrome
– labyrinth disorder that affects the cochlea and the semicircular canals, causing vertigo, nausea, and vomiting
development of the ear
• Ear development begins in the three-week embryo
• Inner ears develop from otic placodes, which invaginate into the otic pit and otic vesicle
• The otic vesicle becomes the membranous labyrinth, and the surrounding mesenchyme
becomes the bony labyrinth
• Middle ear structures develop from the pharyngeal pouches and The brachial groove develops into outer ear structures
• Inner ears develop from otic placodes, which invaginate into the otic pit and otic vesicle
• The otic vesicle becomes the membranous labyrinth, and the surrounding mesenchyme
becomes the bony labyrinth
• Middle ear structures develop from the pharyngeal pouches and The brachial groove develops into outer ear structures
eye and associated structures
• 70% of all sensory receptors are in the eye
• Most of the eye is protected by a cushion of fat and the bony orbit
• Accessory structures include:
– Eyebrows
– Eyelids
– Conjunctiva
– Lacrimal apparatus
– Extrinsic eye muscles
• Most of the eye is protected by a cushion of fat and the bony orbit
• Accessory structures include:
– Eyebrows
– Eyelids
– Conjunctiva
– Lacrimal apparatus
– Extrinsic eye muscles
eyebrows
– Coarse hairs overlie the supraorbital margins
– Functions include:
• Shading the eye
• Preventing perspiration from reaching the eye
– Functions include:
• Shading the eye
• Preventing perspiration from reaching the eye
lacrimal caruncle
– Mass of soft tissue in the medial canthus
– contains glands that secrete a whitish, oily secretion (Sandman’s eye sand)
– contains glands that secrete a whitish, oily secretion (Sandman’s eye sand)
corrugator supercilli origin and insertion
• Origin
– Orbital rim of frontal bone near nasal suture
• Insertion
– Eyebrow
– Orbital rim of frontal bone near nasal suture
• Insertion
– Eyebrow
corrugator supercilli action and innervation
• Action
– move the eyebrows inferiorly and medially
• Innervation
– Facial nerve
– move the eyebrows inferiorly and medially
• Innervation
– Facial nerve
orbicularis oculi origin, insertion, action and innervation
• Origin:
– frontal bone and maxilla, medial margin of orbit
• Insertion:
– tissue around the eyes
• Action:
– depresses the eyebrows
• Innervation
– Facial nerve
– frontal bone and maxilla, medial margin of orbit
• Insertion:
– tissue around the eyes
• Action:
– depresses the eyebrows
• Innervation
– Facial nerve
palpebrae (eyelids)
• Palpebral fissure:
– The gap between the free margins of the lower and upper eyelids
• Eyelashes
– Project from the free margin of the eyelids
– Prevent foreign material from entering the surface of the eye
– The gap between the free margins of the lower and upper eyelids
• Eyelashes
– Project from the free margin of the eyelids
– Prevent foreign material from entering the surface of the eye
tarsal plates
• one in each eyelid.
• An elongated plate of dense connective tissue directly abut the lid margins.
• about 2.5 cm in length
• contributes to its form and support the eyelids internally
• Covered with thin skin
• An elongated plate of dense connective tissue directly abut the lid margins.
• about 2.5 cm in length
• contributes to its form and support the eyelids internally
• Covered with thin skin
tarsal glands
• Located in the inner margin of the eyelid
• secret lipid-rich product that keeps the eyes from sticking together
• secret lipid-rich product that keeps the eyes from sticking together
stye
– inflammation to sebaceous glands or sweat glands at the base of eyelashes
– Small in size, painful, and usually produce no lasting damage
– Small in size, painful, and usually produce no lasting damage
chalazion
– A cyst in the eyelid caused by inflammation of a blocked meibomian (tarsal) gland
– usually on the upper eyelid
– usually painless and larger than stye
– may disappear on its own after a few months, surgery often necessary.
– usually on the upper eyelid
– usually painless and larger than stye
– may disappear on its own after a few months, surgery often necessary.
levator palpebral superioris origin and insertion
• Origin
– Tendinous band around optic foramen
• Insertion
– Upper eyelid
– Tendinous band around optic foramen
• Insertion
– Upper eyelid
levator palpebral superioris action and innervation
• Action
– Elevates upper eyelid
• Innervation
– Oculomotor nerve (III)
– Elevates upper eyelid
• Innervation
– Oculomotor nerve (III)
conjunctiva
– Mucus membrane covered by specialized squamous epithelium that lubricates and protects the eye
– Goblet cells provide lubrication that prevent friction and drying
– Palpebral conjunctiva: Lines the inner surface of the eyelids
– Ocular conjunctiva: Covers the anterior surface of the eye to the edge of the cornea
– Conjunctivitis: inflammation of the conjunctiva
– Goblet cells provide lubrication that prevent friction and drying
– Palpebral conjunctiva: Lines the inner surface of the eyelids
– Ocular conjunctiva: Covers the anterior surface of the eye to the edge of the cornea
– Conjunctivitis: inflammation of the conjunctiva
cornea
– The transparent part of the outer fibrous layer of the eye
– Covered with 5 to 7 layers of delicate squamous epithelium, continuous with the ocular conjunctiva
– Covered with 5 to 7 layers of delicate squamous epithelium, continuous with the ocular conjunctiva
lacrimal apparatus consists of
– lacrimal gland:
– Paired lacrimal canaliculi:
– Lacrimal sac:
– Nasolacrimal duct:
– Paired lacrimal canaliculi:
– Lacrimal sac:
– Nasolacrimal duct:
lacrimal gland
about the size and shape of an almond, measures 12 to 20 mm. Located in the orbit, superior and lateral to the eye ball, within a depression in the frontal bone. Produce 1 ml of tears a day
function of tears
• Slightly alkaline, contain mucus, antibodies, and lysozyme
• Functions:
– Reduce friction, remove debris, prevent bacterial infection, provide nutrients and oxygen to the conjunctiva and cornea
– Lacrimal secretions reach the ocular surface and mixed with the oily secretions of tarsal glands that result in superficial “oil slick” which assist in lubrication and slows evaporation
• Functions:
– Reduce friction, remove debris, prevent bacterial infection, provide nutrients and oxygen to the conjunctiva and cornea
– Lacrimal secretions reach the ocular surface and mixed with the oily secretions of tarsal glands that result in superficial “oil slick” which assist in lubrication and slows evaporation
path of tears
– Tears enter the eye via superolateral excretory ducts
– Blinking sweeps the tears across the ocular surface
– Tears accumulate at the medial canthus
– Exit the eye via the lacrimal punctum which empty into lacrimal canaliculi that leads to the lacrimal sac to the nasolacrimal ducts which empties inferior and lateral to the inferior nasal concha, into the inferior meatus
– Blinking sweeps the tears across the ocular surface
– Tears accumulate at the medial canthus
– Exit the eye via the lacrimal punctum which empty into lacrimal canaliculi that leads to the lacrimal sac to the nasolacrimal ducts which empties inferior and lateral to the inferior nasal concha, into the inferior meatus
structure of the eye ball
• Slightly irregular hollow sphere, located in the orbit, and cushioned by orbital fat
• Measures 24 mm in diameter and weighs 8 grams
• The internal cavity is filled with humor that stabilizes the shape of the eye
• The lens separates the internal cavity into:
– smaller anterior cavity and larger posterior cavity
• The wall is composed of three tunics:
– Outer fibrous, middle vascular, inner neural
• Measures 24 mm in diameter and weighs 8 grams
• The internal cavity is filled with humor that stabilizes the shape of the eye
• The lens separates the internal cavity into:
– smaller anterior cavity and larger posterior cavity
• The wall is composed of three tunics:
– Outer fibrous, middle vascular, inner neural
fibrous tunic: sclera
• Outermost coat of the eye and is opaque sclera, white of the eye with Dense fibrous connective tissue (collagen and elastic) protects the eye
• Thin anteriorly and thick posteriorly, near the optic nerve
• anchors extrinsic eye muscles; the collagen fibers blend with the fibrous tunic
• Contains small blood vessels and nerves that penetrate the sclera to reach the internal structures
• Thin anteriorly and thick posteriorly, near the optic nerve
• anchors extrinsic eye muscles; the collagen fibers blend with the fibrous tunic
• Contains small blood vessels and nerves that penetrate the sclera to reach the internal structures
fibrous tunic: cornea
• Structurally continuous with the sclera
• The collagen fibers organized so as not to interfere with the passage of light
• the borders between the sclera on the cornea called Limbus
• Cornea has no blood vessels, obtain oxygen and nutrients from tears
• Cornea has numerous free nerve endings
• Has restricted ability to repair itself, damage to cornea cause blindness
• The collagen fibers organized so as not to interfere with the passage of light
• the borders between the sclera on the cornea called Limbus
• Cornea has no blood vessels, obtain oxygen and nutrients from tears
• Cornea has numerous free nerve endings
• Has restricted ability to repair itself, damage to cornea cause blindness
vascular tunic functions
aka uvea
– Provides route for blood and lymphatic vessels that supply the eye
– Regulates the amount of light ( iris)
– Secrets aqueous humor
– Controls the shape of the lens
– Provides route for blood and lymphatic vessels that supply the eye
– Regulates the amount of light ( iris)
– Secrets aqueous humor
– Controls the shape of the lens
vascular tunic: Iris
• The colored part of the eye, visible through the cornea that contains blood vessels, pigment cells,
• The body of the iris consists of highly vascular, pigmented, loose connective tissue
• The anterior surface has an incomplete layer of fibroblasts and melanocytes, but no epithelial covering
• The posterior surface covered by pigmented epithelium contains melanin granules and is part of the neural tunic
• The body of the iris consists of highly vascular, pigmented, loose connective tissue
• The anterior surface has an incomplete layer of fibroblasts and melanocytes, but no epithelial covering
• The posterior surface covered by pigmented epithelium contains melanin granules and is part of the neural tunic
vascular tunic: iris muscles
– Pupillary constrictor muscle: concentric circles around the pupil, decrease pupil diameter when contracted (parasympathetic)
– Pupillary dilator muscles: extend radially and enlarge the pupil when contracted (sympathetic)
– Pupillary dilator muscles: extend radially and enlarge the pupil when contracted (sympathetic)
pupil
– the central opening of the iris, regulates the amount of light entering the eye
– Close vision and bright light – pupils constrict
– Distant vision and dim light – pupils dilate
– emotional state: pupils dilate when the matter requires problem-solving skills
– Close vision and bright light – pupils constrict
– Distant vision and dim light – pupils dilate
– emotional state: pupils dilate when the matter requires problem-solving skills
vascular tunic: ciliary body
– A thick ring of tissue surrounding the lens
– Attaches to the iris anteriorly
– Extends posteriorly to the ora serrata
– Composed of smooth muscle (ciliary muscles) and ciliary processes that anchor suspensory ligament which holds the lens in place posterior to the pupil
– Attaches to the iris anteriorly
– Extends posteriorly to the ora serrata
– Composed of smooth muscle (ciliary muscles) and ciliary processes that anchor suspensory ligament which holds the lens in place posterior to the pupil
vascular tunic: choroid region
– A dark brown membrane that forms the posterior portion of the uvea
– vascular layer separates the fibrous and neural tunics posterior to the ora serrata
– Supplies blood to all eye tunics
– Contains melanocytes; numerous near the sclera
– vascular layer separates the fibrous and neural tunics posterior to the ora serrata
– Supplies blood to all eye tunics
– Contains melanocytes; numerous near the sclera
neural tunic: retina
• Delicate Inner most layer
• Has two layers very close together but not tightly interconnected
• Pigmented layer: thin outer layer
• Neural layer: thick inner layer, extends anteriorly to the ora serrata
• Has two layers very close together but not tightly interconnected
• Pigmented layer: thin outer layer
• Neural layer: thick inner layer, extends anteriorly to the ora serrata
neural tunic: retina: pigmented layer
thin outer layer
– absorbs light and prevents its scattering
– Continues over the ciliary body and iris
– absorbs light and prevents its scattering
– Continues over the ciliary body and iris
neural tunic: retina: neural layer contains
Photoreceptors: close to the pigmented layer
Bipolar cells synapse with ganglion cells
Amacrine cells: found where bipolar cells synapse with ganglion cells
horizontal cells: found where bipolar cells synapse with photoreceptors
Horizontal and amacrine facilitate or inhibit communication between photoreceptors and ganglion cells thus altering retinal sensitivity;
important for eye adjustments to dim or bright light
Bipolar cells synapse with ganglion cells
Amacrine cells: found where bipolar cells synapse with ganglion cells
horizontal cells: found where bipolar cells synapse with photoreceptors
Horizontal and amacrine facilitate or inhibit communication between photoreceptors and ganglion cells thus altering retinal sensitivity;
important for eye adjustments to dim or bright light
photoreceptors
• transduce light energy
• synapse with bipolar cells
rods and cones
• synapse with bipolar cells
rods and cones
photoreceptors: rods
– Absorb all wavelengths of visible light
– Do not discriminate among colors; Perceive input is in gray tones
– Highly sensitive to light, respond to dim light; best suited for night vision
– Results in fuzzy and indistinct images
– Are used for peripheral vision
– Sum of visual input from many rods feeds into a single ganglion cell
– Do not discriminate among colors; Perceive input is in gray tones
– Highly sensitive to light, respond to dim light; best suited for night vision
– Results in fuzzy and indistinct images
– Are used for peripheral vision
– Sum of visual input from many rods feeds into a single ganglion cell
photoreceptors: cones
– Need bright light for activation (have low sensitivity)
– Have high-acuity color vision,
– Found in the macula lutea, no rods found here
– Concentrated in the fovea centralis
– Each cone synapses with a single ganglion cell
– Have high-acuity color vision,
– Found in the macula lutea, no rods found here
– Concentrated in the fovea centralis
– Each cone synapses with a single ganglion cell
retina and ganglionic cell axons
– Run along the inner surface of the retina
– Leave the eye as the optic nerve
– Leave the eye as the optic nerve
optic disc
– Circular region medial to the fovea
– Lacks photoreceptors (the blind spot)
– Is the site where the optic nerve leaves the eye to the diencephalon
– The central retinal artery and vein pass through the center of the optic nerve and emerge on the surface of the optic disc
– Lacks photoreceptors (the blind spot)
– Is the site where the optic nerve leaves the eye to the diencephalon
– The central retinal artery and vein pass through the center of the optic nerve and emerge on the surface of the optic disc
blood supply to the retina
• The neural retina receives blood supply from two sources:
– The outer one-third from the choroid
– The inner two-thirds from the central artery and vein
• Small vessels radiate out from the optic disc and can be seen with an ophthalmoscope
– The outer one-third from the choroid
– The inner two-thirds from the central artery and vein
• Small vessels radiate out from the optic disc and can be seen with an ophthalmoscope
posterior segment of the eye
Is filled with a clear gel called vitreous humor that:
– Transmits light
– Supports the posterior surface of the lens
– Holds the neural retina firmly against the pigmented layer
– Contributes to intraocular pressure
– Formed during the development of the eye and it is not replaced
– Transmits light
– Supports the posterior surface of the lens
– Holds the neural retina firmly against the pigmented layer
– Contributes to intraocular pressure
– Formed during the development of the eye and it is not replaced
anterior segment of the eye
• Composed of two chambers filled with aqueous humor
– Anterior: between the cornea and the iris
– Posterior: between the iris and the lens and ciliary body
– Anterior: between the cornea and the iris
– Posterior: between the iris and the lens and ciliary body
anterior segment of the eye and aqueous humor
– A plasma like fluid fills the anterior segment
– Secreted by the ciliary processes into the posterior chamber and passes to the anterior chamber through the pupil and drains via canal of Schlemm into veins in the sclera
– Retain the eye’s shape, stabilizes the position of the retina supports, nourishes, and removes wastes
– Secreted by the ciliary processes into the posterior chamber and passes to the anterior chamber through the pupil and drains via canal of Schlemm into veins in the sclera
– Retain the eye’s shape, stabilizes the position of the retina supports, nourishes, and removes wastes
lens of the eye
• A biconvex, transparent, flexible structure
• Allows precise focusing of light onto the retina
• Covered with fibrous capsule; the fibers intermingle with the suspensory ligaments
• In the interior of the lens have lens fibers; slender and elongated specialized cells that lost their organelle and nuclei and filled with transparent protein called crystallins
• With age, the lens becomes more compact and dense and loses its elasticity
• Allows precise focusing of light onto the retina
• Covered with fibrous capsule; the fibers intermingle with the suspensory ligaments
• In the interior of the lens have lens fibers; slender and elongated specialized cells that lost their organelle and nuclei and filled with transparent protein called crystallins
• With age, the lens becomes more compact and dense and loses its elasticity
refraction and lens
• When light passes from one transparent medium to another its speed changes and it refracts (bends)
• Light passing through a convex lens is bent so that the rays converge to a focal point
• Light passing through a convex lens is bent so that the rays converge to a focal point
focal distance
– The distance between the focal point and the center of the lens
– Focal distance depend on the:
• distance of the object from the lens
• the convexity of the lens
– Focal distance depend on the:
• distance of the object from the lens
• the convexity of the lens
when a convex lens forms an image...
– the image is miniature
– upside down
– reversed right to left
– the brain compensates for the image reversal
– upside down
– reversed right to left
– the brain compensates for the image reversal
focusing light on the retina
• The pathway of light entering the eye:
– cornea, aqueous humor, lens, vitreous humor, neural layer of the retina, photoreceptors
• Light is refracted:
– At the cornea; greatest refraction
– Entering the lens
– Leaving the lens
• The lens curvature and shape allow for fine focusing of an image
– cornea, aqueous humor, lens, vitreous humor, neural layer of the retina, photoreceptors
• Light is refracted:
– At the cornea; greatest refraction
– Entering the lens
– Leaving the lens
• The lens curvature and shape allow for fine focusing of an image
focusing for distant vision
• Light from a distance needs little adjustment for proper focusing
• Far point of vision: the distance beyond which the lens does not need to change shape to focus (20ft)
• Far point of vision: the distance beyond which the lens does not need to change shape to focus (20ft)
focusing for close vision: accommodation
– Ciliary muscle contracts and moves toward the lens
– Suspensory ligaments relax
– The lens becomes more spherical
– Increases refractory power
– Relaxed ciliary muscles make the lens flatter
– Suspensory ligaments relax
– The lens becomes more spherical
– Increases refractory power
– Relaxed ciliary muscles make the lens flatter
focusing for close vision not including accommodation
• Near point of vision:the inner limit of vision
• Constriction:
– the pupillary reflex constricts the pupils to prevent divergent light rays from entering the eye
• Convergence:
– medial rotation of the eyeballs toward the object being viewed
• Constriction:
– the pupillary reflex constricts the pupils to prevent divergent light rays from entering the eye
• Convergence:
– medial rotation of the eyeballs toward the object being viewed
problems of refraction that use corrective lenses to fix
• Emmetropic eye: normal eye with light focused properly
• Myopic eye (nearsighted): the focal point is in front of the retina, corrected with a concave lens
• Hyperopic eye (farsighted): the focal point is behind the retina, corrected with a convex lens
• Astigmatism: the degree of curvature in the cornea or lens varies from one axis to another
• Myopic eye (nearsighted): the focal point is in front of the retina, corrected with a concave lens
• Hyperopic eye (farsighted): the focal point is behind the retina, corrected with a convex lens
• Astigmatism: the degree of curvature in the cornea or lens varies from one axis to another
other problems of refraction
• Blindness: a total absence of vision; caused by total damage to the eye or optic pathway
• Scotomas: A blind spot in the field of vision, other than the optic disc. Permanent abnormalities that are fixed in position.
• Floaters: spot(s) that drift; temporary phenomena
• Scotomas: A blind spot in the field of vision, other than the optic disc. Permanent abnormalities that are fixed in position.
• Floaters: spot(s) that drift; temporary phenomena
light
• Electromagnetic radiation – all energy waves from short gamma rays to long radio waves
• Our eyes respond to a small portion of this spectrum (700-400) called the visible spectrum
• Different cones in the retina respond to different wavelengths of the visible spectrum
• Our eyes respond to a small portion of this spectrum (700-400) called the visible spectrum
• Different cones in the retina respond to different wavelengths of the visible spectrum
anatomy of photoreceptors and the inner segment
– contains cellular organelles
– synapse with other cells, where the neurotransmitters are released
– synapse with other cells, where the neurotransmitters are released
anatomy of photoreceptors and the outer segment and the connecting stalk
– contains discs that have visual pigments that absorb light
• Connecting stalk
– attaches the outer and the inner segments
• Connecting stalk
– attaches the outer and the inner segments
anatomy of photoreceptors general info
• The disc will shed after 10 days in small droplets
• pigmented cells absorb the droplets, breakdown the membrane, and convert the retinal to vitamin A
• vitaminA is stored in pigmented cells and transferred to photoreceptors
• The discs are continuously assembled at the base of the outer segment
• pigmented cells absorb the droplets, breakdown the membrane, and convert the retinal to vitamin A
• vitaminA is stored in pigmented cells and transferred to photoreceptors
• The discs are continuously assembled at the base of the outer segment
rods
– Elongated cylinder outer segment
– Each disc is an independent entity
– The visual pigment is rodopsin
– Rodopsin: consist of a protein opsin bound to the pigment retinal (synthesized from vitamin A)
– One opsin is characteristic of all rods
Rod and cones refer to the outer segment’s shape
– Each disc is an independent entity
– The visual pigment is rodopsin
– Rodopsin: consist of a protein opsin bound to the pigment retinal (synthesized from vitamin A)
– One opsin is characteristic of all rods
Rod and cones refer to the outer segment’s shape
cones
– The outer segment tapers
– The discs are infoldings of the cell membrane
– Have the same retinal as rods but different opsin that determine the light wavelength to be absorbed
Rods and cones refer to the outer segment’s shape
– The discs are infoldings of the cell membrane
– Have the same retinal as rods but different opsin that determine the light wavelength to be absorbed
Rods and cones refer to the outer segment’s shape
photoreception
• The outer segment of the cell membrane contains chemically regulated Na channels. In the dark, the channels are kept open in the presence of cGMP
• the photoreceptors are continuously releasing neurotransmitter across synapses in the inner segment; The membrane potential is - 40mv
• The inner segment continuously pumps Na out of the cytoplasm
• Dark current is the movements of Na ions into the outer segment on to the inner segment and out of the cell
• the photoreceptors are continuously releasing neurotransmitter across synapses in the inner segment; The membrane potential is - 40mv
• The inner segment continuously pumps Na out of the cytoplasm
• Dark current is the movements of Na ions into the outer segment on to the inner segment and out of the cell
photoreception and changes in the opsin
• The photon strikes the retinal, changing it from 11-cis to 11-trans form which activates the opsin molecule
• Opsin activates transduction (G protein) which activates phosophdiesterase; PDE breaks down cGMP which results in inactivation of Na channels
• The dark current reduces and the potential drops to -70mv (hyperpolarization).
• This results in a decrease the neurotransmitter release, indicating to the bipolar cells that the photoreceptors has absorbed a photon
• Opsin activates transduction (G protein) which activates phosophdiesterase; PDE breaks down cGMP which results in inactivation of Na channels
• The dark current reduces and the potential drops to -70mv (hyperpolarization).
• This results in a decrease the neurotransmitter release, indicating to the bipolar cells that the photoreceptors has absorbed a photon
recovery after retina stimulation
• Bleaching: The rodopsin begins to break down
• The retinal is then converted to 11-cis form (requires ATP) and binds to opsin to make rodopsin
• The membrane permeability returns to normal
• Other enzymes generate cGMP
• Chemically gated Na ion channels reopen
• Insufficient vitaminA can lead to decrease amount of visual pigment which result in night blindness
• The retinal is then converted to 11-cis form (requires ATP) and binds to opsin to make rodopsin
• The membrane permeability returns to normal
• Other enzymes generate cGMP
• Chemically gated Na ion channels reopen
• Insufficient vitaminA can lead to decrease amount of visual pigment which result in night blindness
color vision
• You see white light when photon stimulate rods alone or all three cones
• If all photons bounce off the object you see white
• If all photons absorbed by the object you see black
• Intermediate colors are perceived by activation of more than one type of cone
• Method of excitation is similar to rods
• If all photons bounce off the object you see white
• If all photons absorbed by the object you see black
• Intermediate colors are perceived by activation of more than one type of cone
• Method of excitation is similar to rods
three types of cones
– Blue (16%), Red (74%), Green (10%)
– Each have different kind of opsin
– Each sensitive to a specific wavelength
• Color blindness: unable to see certain color due to non functional cones
– Each have different kind of opsin
– Each sensitive to a specific wavelength
• Color blindness: unable to see certain color due to non functional cones
adaptation to bright light
– Dramatic decreases in retinal sensitivity – rod function is lost
– Switching from the rod to the cone system – visual acuity is gained
– Switching from the rod to the cone system – visual acuity is gained
adaptation to dark
– Cones stop functioning in low light
– Rhodopsin accumulates in the dark and retinal sensitivity is restored
– Rhodopsin accumulates in the dark and retinal sensitivity is restored
visual pathways
• Medial fibers of the optic nerve decussate at the optic chiasm
• Most fibers of the optic tracts continue to the lateral geniculate body of the thalamus,
• Optic radiations travel from the thalamus to the visual cortex
• Some nerve fibers send tracts to the superior colliculi and hypothalamus
• Visual information from the left half of both fields reach the right occipital lobe and vice versa
• Most fibers of the optic tracts continue to the lateral geniculate body of the thalamus,
• Optic radiations travel from the thalamus to the visual cortex
• Some nerve fibers send tracts to the superior colliculi and hypothalamus
• Visual information from the left half of both fields reach the right occipital lobe and vice versa
depth perception
• Achieved by both eyes viewing the same image from slightly different angles
• Three-dimensional vision results from cortical fusion of the slightly different images
• If only one eye is used, depth perception is lost and the observer must rely on learned clues to determine depth
• Three-dimensional vision results from cortical fusion of the slightly different images
• If only one eye is used, depth perception is lost and the observer must rely on learned clues to determine depth
developmental aspects of vision
• Vision is not fully functional at birth
• Babies are hyperopic (farsighted)
• see only gray tones
• eye movements are uncoordinated
• Depth perception and color vision is well developed by age five
• emmetropic eyes are developed by year six
• With age the lens loses clarity, dilator muscles are less efficient, and visual acuity is drastically decreased by age 70
• Babies are hyperopic (farsighted)
• see only gray tones
• eye movements are uncoordinated
• Depth perception and color vision is well developed by age five
• emmetropic eyes are developed by year six
• With age the lens loses clarity, dilator muscles are less efficient, and visual acuity is drastically decreased by age 70
About this deck
By: Amanda Duncan
Created: 2012-04-30
Size: 143 flashcards
Views: 17
Created: 2012-04-30
Size: 143 flashcards
Views: 17
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