Chapter 8 Flashcards
Special senses include
Smell
Taste
Sight
Hearing
Equilibrium
Special sense receptors
Large, complex sensory organs (eye and ear)
Localized clusters of receptors (taste buds and olfactory epithelium)
70 Percent of all sensory receptors are in
Eyes
How many nerve fibers in each eye?
Over 1 million nerve fibers per eye
Accessory structures in eye
Extrinsic eye muscles
Eyelids
Conjunctiva
Lacrimal apparatus
Extrinsic eye muscles
Eye movement
Conjunctiva
Cover sclera and cornea (connects w/)
Membrane line eyelids & eyeballs
Palpebra
Eyelid
Eyelids meet in
Commisure or canthus
Lateral commissure
Outer corner of eye
Medial commissure of eye
Inner corner of eye
Sclera
White part
Covered by conjunctiva
Iris
Colored part of eye
Cornea
Clear part of sclera
Pupil
Dark part of eye
Photons of light pass
Meets at medial and lateral commisures
Eyelids
Eyelashes
Prevent injury, keep debris out
Tarsal glands
Produce oily secretion that lubricates eye
Mebum
Oily secretion that lubricates eye
Ciliary glands located
Between eyelashes
What secretes mucus to lubricate the eye and keep it moist
Conjunctiva
Parts of Lacrimal apparatus
Lacrimal gland
Ducts
Lacrimal gland
Lacrimal fluid
On lateral end of each eye
Explain how tears drain
- Drain across eye into Lacrimal canaliculi
- Lacrimal sac
- Nasolacrimal duct
- Empties into Nasal cavity
What is inside tears?
Dilute salt solution
Mucus
Antibodies
Lysozyme (enzyme destroys bacteria)
Function of tears
Cleanse
Protect
Moisten
Lubricate eye
Extrinsic eye muscles
Attach to outer surface of the eye
Make gross eye movement
Name the extrinsic muscles of the eye
Superior, inferior oblique
2 Lateral, superior, inferior rectuses
Trochlea
Anchored superior oblique
Lateral rectus action
Moves eye laterally
Controlling cranial nerve of lateral rectus
VI
Abducens
Medial rectus action
Moves eye medially
Medial rectus controlled by
III (oculomotor)
Superior rectus action
Elevates eye
Turns it medially
Superior rectus controlled by
III oculomotor
Inferior rectus action
Depresses eye
Turns it medially
Inferior rectus controlled by
III oculomotor
Inferior oblique action
Elevates eye and turns it laterally
Inferior oblique controlling cranial nerve
III oculomotor
Superior oblique action
Depresses eye & turns laterally
Controlling cranial nerve superior oblique
IV (trochlear)
Tunics of eyeball
Fibrous
Vascular
Sensory
Humors
Fluids that fill inside of eyeball
Give shape
Lens divides eye into
Two chambers
Anterior posterior chambers
Fibrous layer
Outside layer
Sclera
Vascular layer
Middle layer
Sensory layer
Inside layer
Photoreceptors and pigment layer
Outermost fibrous layer of eye
Sclera
Middle layer or eye
Choroid
Vascular
Retina
Innermost layer
Sensory
rods
Cones
Photoreceptors
Focused light directed to
Fovea Centralis
Fovea Centralis
Higher concentration of photoreceptors
More cones
Higher visual acuity
Parts of fibrous layer
Sclera+ cornea
Cornea
Transparent,
Central anterior portion
Lets light pass through
What repairs itself easily?
Cornea
Only human tissue that can be transplanted w/o fear of rejection
Cornea (lack of blood vessels)
Choroid
Blood rich
Nutritive layer
Pigment that prevents light from scattering
Choroid modified anteriorly into two smooth muscle structures known as
Ciliary body
Iris
Ciliary body
Attached to lens by suspensory ligament called ciliary zonule
Iris
Regulates amount of light entering eye
Function of pigmented layer of iris
Gives eye color
Pupil
Rounded opening in iris
Point where light enters into eye from cornea
Pupil
Light passes from cornea to
Lens and after to retina
Layers of retina
Pigmented layer
Inner Neural layer
Inner neural layer
Has rods and cones
Outer pigmented layer
Absorbs light and prevents it from scattering
Sensory layer
Signals pass from photoreceptors via a
Two neuron chain
Two neuron chain made of
Bipolar cells
Ganglion cells
Signals leave retina towards brain through
Optic nerve
Optic disc
Blind spot
Optic nerve leaves eyeball
Cannot see images focused on
Optic disc
Phototransduction
Specialized outer segment of photoreceptors
Capture light and converts into electrical signals
Photoreceptors (rods)
Pick up photons peripheral vision
Cones
visualize visible light. Different colors
Axons of ganglion cells make
optic nerve
Three major types of neurons that make retina
Rods (photoreceptors)
Cones (visible light)
Bipolar cells
Central artery and vein of retina
Rich blood supply to and from eye
Rods found in
Edges of retina
What allows vision in dim light?
Rods
What allows peripheral vision
Rods
Perception is in grey tones
Rods
Where are cones densest ?
Center of retina
Fovea Centralis location
Lateral to blind spot
Area of retina w/ only cones
Fovea Centralis
Highest visual acuity
Fovea Centralis
No ______ are at the optic disc or blind spot
Photoreceptor cells
Allow for detailed color vision
Cones
Point where optic nerve enters and exits eye
Optic disc
Photopsin 1
Red pigments
Photopsin 2
Green
Photopsin 3
Blue or violet pigments
Lens
Flexible,
Biconvex crystal-like structure
Lens held in place by
Held by suspensory ligament attached to ciliary body
Lens sits posterior to
Iris
Cornea
Pupil
Lens flexibility helps it
Focus and accommodate light passing through lens
Explain how focus happens
Ciliary muscle pulls on lens to let focus
Ciliary zonule
Suspensory ligaments
Aqueous segment
Anterior segment of lens
Has aqueous humor
Vitreous segment
Posterior segment of lens
Gel like vitreous humor
Aqueous humor
Watery fluid between lens and cornea, sim. to plasma
What helps maintain intraocular pressure?
Aqueous humor
Function of aqueous humor
Maintain intraocular pressure
Nutrients for lens and cornea
How is aqueous humor reabsorbed?
Scleral venous sinus
Canal of schlemm
Vitreous humor function
Prevents eye from collapsing
Maintain intraocular pressure
Ophthalmoscope
Illuminates inside of eyeball and fundus
Fundus
Posterior wall of eye
What can ophthalmoscopes detect?
Diabetes, arteriosclerosis,
Degeneration of optic nerve and retina
Dark area of eye
Macula
Houses fovea centralis
For optimal vision, light must be
Focused to a point on the retina for optimal vision (fovea centralis)
What bends or refracts light?
Cornea
Aqueous humor
Lens
Vitreous humor
Eye is set for _____ vision over 20 ft away
Distant
Accomodation
Lens must change shape to focus on objects less than 20 ft away
When looking at light from distant source lens is
Flatter
When looking at light from closer source lens is
More curved
Image formed on retina is a
Real image
Real images are:
Reversed from left to right
Upside down
Smaller than the object
Visual fields and visual pathways to the brain
Optic nerve
Optic chiasma
Optic tracts
Optic radiation
Optic nerve
Bundle of axons that exit back of eye carrying impulses through retina
Optic chiasma
Location where optic nerves cross
Fibers from the medial side of each eye cross over to the opposite side of the brain
Signals passed through ____ to the optic nerve
Transduction
Optic tracts synapse with
Synapse w/ neurons in thalamus
Optic tracts contain
Fibers from lateral side of eye on same lateral side
Fibers from medial side come from the opposite eye
Optic radiation
Axons from thalamus run to the occipital lobe
Optic radiation synapse with
Cortical cells and vision interpretation (sight) happens
Summary of the pathway from retina to point of visual interpretation
- Optic nerve
- Optic chiasma
- Optic tract
- Thalamus
- Optic radiation
- Visual cortex in occipital lobe of brain
Left visual field ends up on
Right cortex and vice versa
Binocular vision results and provides
Depth perception (3D vision)
Each eye sees a
Slightly different view
Field of view _____ for each eye
Overlaps
Emmetropia
Normal eye vision
Eye focuses images correctly on retina
Myopia
Nearsightedness
Myopia results from
Too long eyeball
How do distant objects appear with myopia
Blurry
What happens in myopia
Light from objects fails to reach retina
Focused in front of it
Hyperopia
Farsightedness
In hyperopia near objects are
Blurry, distant objects are clear
Describe focus in hyperopia
Distant objects focused behind retina
Hyperopia results from
Too short eyeball
or
“Lazy lens”
Astigmatism
Images are blurry
Unequal curvature of cornea or lens
Astigmatism results from
Light focusing as lines not points on the retina because of unequal curvatures of the cornea or lens
Concave lens correct which eye
Myopic
Move focus point further back
Convex lens move focal point ______ fix ______ eye
Forward
Hyperopic
Cylindrically ground lenses fix
Astigmatism
Convergence
Reflexive movement of the eyes medially when we focus on a close object
Photopupillary reflex
Bright light causes pupils to constrict
Accomodation pupillary reflex
Viewing close objects causes pupils to constrict
Ear houses 2 senses
Hearing
Equilibrium
Receptors in ear are called
Mechanoreceptors
Three areas of ear
External
Middle
Internal
Auricle aka
Pinna
Auricle or pinna is
Outer ear
Visible portion
Directs sound waves to canal
Parts of outer ear
Pinna (auricle)
External acoustic meatus
External acoustic meatus
Auditory canal
Narrow chamber in temporal bone
Lined with ceruminous glands
Cerumen
Earwax
Traps foreign objects
Repels insects
External acoustic meatus ends at
Tympanic membrane
Tympanic membrane is aka
Eardrum
Middle ear cavity
Tympanic cavity
Air filled, mucosa lined cavity within temporal bone
Tympanic cavity
Tympanic cavity is only involved in
Sense of hearing
Tympanic cavity location
Between tympanic membrane (laterally)
Medially by bony wall w/ two openings
Oval window
Round window
Pharyngotympanic tube
links middle ear cavity with throat
Equalizes pressure in middle ear cavity so eardrum can vibrate
Ossicles (bones) inside tympanic cavity
Malleus (hammer)
Incus (anvil)
Stapes (stirrup)
Function of ossicles in middle ear
Transmit and amplify vibrations from tympanic membranes to fluids in the inner ear
Describe how vibrations travel in middle ear
Hammer>anvil>stirrup> oval window of inner ear
Hammer attached to
Tympanic membrane
Inner ear includes sense organs for
Hearing and balance
Bony labyrinth consists of
Cochlea
Vestibule
Semicircular canals
Bony labyrinth is filled with
Perilymph
Membranous labyrinth is suspended in _______
Perilymph
Membranous labyrinth contains
Endolymph
Parts of inner ear
Bony labyrinth
Spiral organ of corti located within
Cochlear duct
Spiral organ of corti
Has receptors=hair cells on basilar membrane
Gel, like tectorial membrane that can bend hair cells
Cochlear nerve attached to the hair cells transmits nerve impulses to
Auditory cortex on temporal lobe
Pathway of vibrations from sound waves
- Auricle (pinna)
- External acoustic meatus
- Tympanic membrane
- Ossicles amplify sounds
- Oval window
- Basilar membrane in spiral organ of corti
- Hair cells of tectorial membrane bent when basilar membrane moves against it
- Action potential starts in cochlear nerve (cranial nerve 8)
- Impulse travels to auditory cortex in temporal lobe
High pitched sounds disturb
Short, stiff fibers of basilar membrane
Receptor cells close to oval window are stimulated
Low pitched sounds disturb
Long, floppy fibers of basilar membrane
-specific hair cells further along cochlea are affected
Vestibular apparatus
Equilibrium receptors of inner ear
Vestibular apparatus has two functional parts
Static and dynamic equilibrium
Maculae
Receptor in vestibule
Report on position of head
Help keep head erect
How do maculae send information
Via vestibular nerve (part of cranial nerve 8) to cerebellum of brain
Anatomy of maculae
Hair cells embedded in otolithic membrane
Otoliths float in gel around hair cells
What causes otoliths to roll and bend hair cells
Movements
Otoliths
Tiny stones
Oto-
Ear
-Lith
Stone
Crista ampullaris
Responds to angular or rotational movements of head
Crista ampullaris location
In ampulla (expanded portion) of each semicircular canal
Tuft of hair cells in Crista ampullaris covered w/
Cupula (gelatinous cap)
If the head moves, the cupula,
Drags against the endolymph
If cupula drags against endolymph,
Hair cells are stimulated,
Impulse travels the vestibular nerve to the cerebellum
Deafness
Any degree of hearing loss
Conduction deafness
Sound vibrations hindered through external and middle ear
Sensorineural deafness
Damage to nervous system structures involved in hearing
Menieres syndrome
Affects inner ear
Progressive deafness
Often vertigo
Chemical senses
Smell
Taste
Chemoreceptors
Stimulated by chemicals
Taste has _ types of receptors
5
Smell can differentiate a
Wider range of chemicals
Taste and smell compliment each other; respond to
Many of same stimuli
Olfactory receptors are in
Roof of nasal cavity
Olfactory receptor cells are a type of
Neuron
Olfactory hairs
Long cilia on olfactory receptor cells
Detect chemicals
Olfactory receptors can only detect chemicals that are
Dissolved in mucus
Impulses are transmitted via the olfactory
Filaments to cranial nerve I (olfactory nerve)
Smells are interpreted in
The olfactory cortex
Taste buds house
Receptor organs
Locations of taste buds
Most of tongue
Soft palate
Superior part of pharynx
Cheeks
Tongue covered w/ projections called
Papillae
Fungiform papillae
Bumps on tongue
Button like
Foliate papillae
Ribbed lines on side of tongue
Vallate papillae
Posterior aspect of tongue
Straight line
Concentric nodules
Highest # of taste buds
Largest of taste buds
Gustatory cells
Taste receptors
Have gustatory hairs
Gustatory hairs
Long microvilli
Protrude through taste pore
How are gustatory hairs stimulated
Chemicals dissolved in saliva
Gustatory cells synapse with
Sensory nerve fibers and through basal cells into connective tissue layer
Impulses carried to gustatory complex by several cranial nerves because
Taste buds found in different areas
Taste buds are frequently replaced by
Basal cells
Nerves that carry gustatory impulses
Facial nerve (7)
Glossopharyngeal nerve (9)
Vagus nerve (cranial nerve 10)
Neuronal cells capable of regeneration
Taste buds
Olfactory cells
Sweet receptors
Most on top of tongue
Respond to sugars, saccharine,
Some aminoacids
Sour receptors respond to
H+ ions or acids
Sides
Bitter receptors respond to
Alkaloids
Salty receptors respond to
Metal ions
Umami receptors respond to
Amino acid glutamate
Or beefy taste of meat