BIO 241 Final Exam

Conjunctivitis

- Inflammation of the conjunctiva resulting in reddened, irritated eyes - May be allergic, viral, bacterial

Otitis media

- Middle ear inflammation - Commonly seen in children with sore throat • Especially those with shorter, more horizontal pharyngotympanic tubes - Most frequent cause of hearing loss in children - Acute infectious forms cause eardrum to bulge outward & become inflamed • Most cases respond to antibiotics

Extrinsic eye: Superior rectus

B Elevates eye and turns it medially III (oculomotor)

Bulbar Conjunctiva

B membrane that covers white of eyes (not cornea) Small blood vessels found in this membrane; seen easily in "bloodshot" eyes

Ciliary Body (Middle Vascular Layer)

Body (B) Zonule (C) • Anteriorly, choroid becomes ciliary body • Thickened ring of tissue surrounding lens • Consists of smooth muscle bundles that control shape of lens • Capillaries secrete fluid for anterior segment of eyeball • Ciliary zonules (suspensory ligaments) extend from ciliary body to lens to hold lens in position

Hyperopia

(farsightedness) • Eyeball is too short, so focal point is behind retina • Corrected with convex lens

Myopia

(nearsightedness) • Eyeball is too long, so focal point is in front of retina • Corrected with concave lens

Conjunctiva

Transparent mucous membrane that produces lubricating mucous secretion

Extrinsic eye: Superior oblique

C Depresses eye and turns it laterally IV (trochlear)

Vestibule

• Central egg-shaped cavity of bony labyrinth - Contains two membranous sacs housing equilibrium receptor regions (maculae) that respond to gravity & changes in position of head 1. Saccule, continuous with cochlear duct 2. Utricle, continuous with semicircular canals

Sphincter pupillae

Causes pupil to constrict - circular muscle - triggered by lose vision, bright light - under parasympathetic control

Sound Detection

• Hearing is reception of an air sound wave that is converted to a fluid wave • Sound = pressure disturbance (alternating areas of high & low pressure) produced by vibrating object - Sound wave moves outward in all directions - Described by two physical properties: frequency & amplitude

Astigmatism

• Unequal curvatures in different parts of cornea or lens • Corrected with cylindrically ground lenses or laser procedures

Palpebral Conjunctiva

A Membrane that lines underside of eyelids

Extrinsic eye: lateral rectus

A Moves eye laterally VI Abducens

Extrinsic eye: Medial rectus

D Moves eye medially III (oculomotor)

Extrinsic eye: Inferior oblique

F Elevates eye and turns it laterally III (oculomotor)

Structural Types

Fibrous, Cartilaginous, Synovial

Iris

Iris: E Pupil: F Iris ("Eye color") • Lies between cornea & lens, continuous with ciliary body • Pupil - Central opening

Functional Joints Structure

Joined by dense fibrous connective tissue

Choroid region (Middle Vascular Layer)

• Posterior portion • Supplies blood to all layers of eyeball • Brown pigment absorbs light to prevent scattering of light, which would cause visual confusion

Maculae

• Sensory receptor organs that monitor static equilibrium - One located in each saccule wall & one in each utricle wall • Monitor position of head in space • Play key role in control of posture • Respond to linear acceleration forces, but not rotation

Cochlea

• Small spiral, conical, bony chamber, size of split pea - Extends from vestibule - Coils around bony pillar (modiolus) - Contains cochlear duct (13), which houses spiral organ (12) (organ of Corti) & ends at cochlear apex

Convex

- Curving outward, like a sexy, vexy breast"; view of bowl as table - Convex lenses bend light --> rays converge at one focal point * Image formed at focal point is up-side down and revered left to right.

Retinal Isomers

- Different 3-D forms • Retinal is in bent form in dark - cis-retinal • When pigment absorbs light, it straightens out - trans-retinal - Conversion of bent to straight initiates reactions that lead to electrical impulses along optic nerv

Glaucoma

- Drainage of aqueous humor is blocked, causing fluid to back up & increase pressure within eye - Pressure may increase to dangerous levels & compress retina & optic nerve, leading to blindness - Few early signs, but late signs include seeing halos around lights & blurred vision - Detected by directing puff of air at cornea & measuring amount of corneal deformation • Too much pressure = not enough deformation

Focusing for Close Vision

Light from close objects diverges - Requires eye to make active adjustments using three simultaneous processes: 1. Accommodation of lenses - Changing lens shape to increase refraction - Ciliary muscles are contracted in close vision --> ciliary zonules loosen --> lenses allowed to bulge 2. Constriction of pupils - Prevents most divergent light rays from entering eye - Mediated by parasympathetic nervous system 3. Convergence of eyeballs - Medial rotation of eyeballs toward object being viewed

Light Transduction Reactions

Light-activated rhodopsin triggers "molecular relay race" - In dark, cation channels of outer segment are held open • Na+ & Ca2+ enter --> cell depolarizes - In light, channels close, cell hyperpolarizes • Hyperpolarization is signal for vision!

Steps of Phototransduction

Pigment synthesis - Opsin & cis retinal combine to form rhodopsin in dark • Pigment bleaching - When rhodopsin absorbs light, cis isomer of retinal changes to trans isomer - Retinal & opsin separate (rhodopsin breakdown) • Pigment regeneration - trans retinal converted back to cis isomer - Rhodopsin is regenerated in outer segments

Macula lutea

• Cones - Vision receptors for bright light - High-resolution color vision • Macula lutea (O) - Cone hotspot - Appears as dark disc through opthalmoscope

Rods

• Dim light, peripheral vision receptors • More numerous & more sensitive to light than cones • No color vision or sharp images • Numbers greatest at periphery

Structural Class

Three types based on the material of the joints that bind them together and whether it has a cavity.

Functional Class

Three types of joints based on the movement the joints allow

Function of Eyebrow

To shade eyes from the sun, to prevent perspiration reaching eyes.

Cornea (outermost fibrous layer)

B - Transparent anterior one -sixth of fibrous layer - Forms clear window: light enters & bends - Epithelium covers both surfaces - Outer surface protects from abrasions - Inner layer contains Na2+ pumps (help maintain clarity) - Pain receptors contribute to blinking & tearing reflexes

Refraction

Bending of light rays - Due to change in speed of light when it passes from one transparent medium to another and path of light is at an oblique angle - lenses of eyes can also refract light because they are curved on both sides

Lens

Biconvex, transparent, flexible, avascular - Changes shape to precisely focus light on retina - Lens fibers form bulk of lens • Filled with transparent protein crystallin • Continuously added, so lens becomes more dense, convex, & less elastic with age

Dilator pupillae

Causes pupil to dilate - Radial muscle - triggered by distant vision, dim light, appealing subject matter, problem-solving, excitement - under sympathetic control

Lacrimal Apparatus

Consists of lacrimal gland & ducts that drain into nasal cavity

Pathway of Light

Cornea --> aqueous humor --> lens -- vitreous humor --> neural layer of retina --> photoreceptors Light is refracted three times along path: (1) entering cornea (2) entering lens (3) leaving lens - Majority of refractory power is in cornea • Though constant & cannot change focus - Curvature of lens is adjustable (via ciliary muscles) • Can focus for distant vision or for close vision

Extrinsic eye: Inferior rectus

E Depresses eye and turns it medially III (oculomotor)

Color blindness

Lack of one or more cone pigments • Inherited as an X-linked condition, so more common in males

Functions of joints

Mobility and hold skeleton together

Homeostatic Imbalance 15.3

Nasal cavity mucosa is continuous with mucosa of lacrimal duct system, so a cold or nasal inflammation often causes lacrimal mucosa to swell - May provide microbes access to eyes (conjunctivitis) - Swelling constricts the ducts & prevents tears from draining, causing "watery" eyes

Concave

- "Caving inward", view of bowl as cereal - Concave lenses disperse light --> prevent focus

Cataract

- Clouding of lens due to clumping of crystallin proteins • Consequence of aging, diabetes mellitus, heavy smoking, frequent exposure to intense sunlight, vitamin C; some congenital • Lens can be replaced surgically with artificial lens

Activating receptors of a macula

- Hair cells release neurotransmitter continuously •Acceleration/deceleration causes a change in amount of neurotransmitter released - Leads to change in AP frequency to brain - Density of otolith membrane causes it to lag behind movement of hair cells when head changes positions • Base of stereocilia moves at same rate as head, but tips embedded in otolith are pulled by lagging membrane, causing hair to bend • Ion channels open, and depolarization occurs

Sclera (outermost fibrous layer)

- Opaque posterior region - Protects & shapes eyeball - Anchors extrinsic eye muscles - Posteriorly, where optic nerve exits, sclera is continuous with dura mater of brain

Lacrimal gland

3 • Located in orbit above lateral end of eye • Secretes tears - Dilute saline solution containing mucus, antibodies, antibacterial lysozyme - Blinking spreads tears - Tears drain into lacrimal sac, which empties into nasal cavity

Function

Synarthroses, amphiarthroses, diarthroses

lacrimal sac

Tears drain into lacrimal sac, which empties into nasal cavity

Neural Layer of Retina

Transparent layer that runs anteriorly to margin of ciliary body • Composed of three main types of neurons 1. Photoreceptors 2. bipolar cells 3. ganglion cells - Signals spread: photoreceptors --> bipolar cells --> ganglion cells - Ganglion cell axons exit eye as optic nerve - Optic disc • Site where optic nerve leaves eye • Lacks photoreceptors, so referred to as blind spot - Retina has quarter-billion photoreceptors of two types: • Rods • Cone

Pinkeye

conjunctival infection caused by bacteria or viruses - Highly contagious

Internal Ear

• Also referred to as the labyrinth • Located in temporal bone behind eye socket • Two major divisions: - Bony labyrinth: system of twisting channels & cavities that worm through bone • Divided into three regions: vestibule, semicircular canals, cochlea • Filled with perilymph fluid; similar to CSF - Membranous labyrinth; series of membranous sacs & ducts within bony labyrinth; filled with potassium-rich endolymph

Deafness

• Conduction deafness - Blocked sound conduction to fluids of internal ear • Causes include impacted earwax, perforated eardrum, otitis media, otosclerosis of the ossicles • Sensorineural deafness - Damage to neural structures at any point from cochlear hair cells to auditory cortical cells - Typically from gradual hair cell loss

Activating Receptors of Crista Ampullaris

• Cristae respond to changes in velocity • Inertia in ampullary cupula causes endolymph in semicircular ducts to move in direction opposite body's rotation, causing hair cells to bend • Bending hairs in cristae causes depolarization - Rapid impulses reach brain at faster rate • Bending hairs in opposite direction causes hyperpolarization - Fewer impulses reach brain • Axes of hair cells in complementary semicircular ducts are opposite - Depolarization occurs in one ear, while hyperpolarization occurs in other ear - Endolymph will come to rest after a while, so this system detects only changes in movements

Anatomy of a Crista Ampullaris

• Each crista has supporting cells & hair cells that extend into gel-like mass called ampullary cupula • Dendrites of vestibular nerve fibers encircle base of hair cells

Sound Transduction: Excitation of Inner Hair Cells

• Movement of basilar membrane deflects hairs of inner hair cells - Cochlear hair cells have stereocilia (hairs) that bend at their base - Longest stereocilia are enmeshed in gel-like tectorial membrane & connected to shortest stereocilia via tip links - Tip links, when pulled on, open ion channels they are connected to • Bending of stereocilia toward shorter ones causes tip links to relax - Ion channels close, leading to repolarization (even hyperpolarization)

Role of Outer Hair Cells

• Nerve fibers coiled around hair cells of outer row are efferent neurons that convey messages from brain to ear - Outer hair cells can contract & stretch, which changes stiffness of basilar membrane - This ability serves two functions: • Increase "fine-tuning" responsiveness of inner hair cells by amplifying motion of basilar membrane • Protect inner hair cells from loud noises by decreasing motion of basilar membrane

Frequency

• Number of waves that pass given point in given time • Pure tone has repeating crests & troughs • Wavelength - Distance between two consecutive crests - Shorter wavelength = higher frequency of sound • Pitch - Perception of different frequencies - Normal range 20-20,000 hertz (Hz) - Higher frequency = higher pitch • Quality - Most sounds mixtures of different frequencies - Richness & complexity of sounds (music)

Inner pigmented layer Retina

• Originates as an outpocketing of brain • Contains: - Millions of photoreceptor cells that transduce light energy - Neurons - Glial cells • Delicate two - layered membrane: - Outer pigmented layer • Single-cell-thick lining next to choroid • Extends anteriorly, covering ciliary body and iris • Functions: - Absorbs light and prevents its scattering - Phagocytizes photoreceptor cell fragments - Stores vitamin A - Inner neural layer

Structure of the Eyeball

• Wall of eyeball contains layers - Outermost fibrous layer of dense, avascular connective tissue: sclera & cornea - Middle vascular layer: choroid, ciliary body, iris - Inner retina • Filled internally with fluids called humors • Lens separates internal cavity into anterior & posterior segments

Anatomy of a Macula

• Each is flat epithelium patch containing hair cells with supporting cells - Hair cells have stereocilia, embedded in otolith membrane, jelly-like mass studded with otoliths (tiny CaCO3 stones) • Otoliths increase membrane's weight & increase its inertia (resistance to changes in motion) - Utricle maculae are horizontal with vertical hairs • Respond to change along a horizontal plane, such as tilting head - Forward/backward movements stimulate utricle - Saccule maculae are vertical with horizontal hairs • Respond to change along a vertical plane - Up/down movements stimulate saccule (Example: acceleration of an elevator)

Maintenance of Equilibrium

• Equilibrium is response to various movements of head that rely on input from inner ear, eyes, & stretch receptors • Vestibular apparatus: equilibrium receptors in semicircular canals and vestibule - Vestibular receptors monitor static equilibrium - Semicircular canal receptors monitor dynamic equilibrium

Focusing for Distant Vision

• Far point of vision: distance beyond which no change in lens shape is needed (in normal eye) for focusing - Light focused precisely on retina at this distance - (Versus near point of vision: closest distance at which eye can focus) • Eyes are best adapted for distant vision • Ciliary muscles are completely relaxed in distant vision --> pull on ciliary zonules --> lenses stretched flat

Amplitude

• Height of crests • Perceived as loudness • Measured in decibels (dB) - Normal range is 0-120 decibels (dB) - Severe hearing loss can occur with prolonged exposure above 90 dB • Amplified rock music is 120 dB or more

Anterior and Posterior Segment of Eye

• Lens & ciliary zonule separate eye into two segments - Posterior segment (B) • Contains vitreous humor - Transmits light, supports posterior surface of lens, holds neural layer of retina firmly against pigmented layer, & contributes to intraocular pressure - Forms in embryo & lasts lifetime - Anterior segment (A) • Iris divides anterior segment into two chambers: - Anterior chamber—between cornea & iris - Posterior chamber—between iris & lens • Entire segment contains aqueous humor - Plasma-like fluid continuously formed by capillaries of ciliary body - Supplies nutrients & O2 to lens, cornea, retina, - Removes wastes

Auditory Processing

Perception of pitch: impulses from hair cells in different positions along basilar membrane are interpreted by brain as specific pitches • Detection of loudness is determined by brain as an increase in the number of action potentials (frequency) that result when hair cells experience larger deflections • Localization of sound depends on relative intensity & relative timing of sound waves reaching both ears - If timing is increased on one side, brain interprets sound as coming from that side

Function of Eyelids and Eyelashes (Palpebrae)

Protect eye anteriorly

Pupil

Regulate amount of light entering eye

Transmission of Sound to Internal Ear

• Pathway of sound 1. Sound waves vibrate tympanic membrane The higher the intensity, the more vibration 2. Auditory ossicles transfer vibration of eardrum to oval window Tympanic membrane is about 20x larger than oval window, so vibration transferred to oval window is amplified about 20x 3. Pressure waves move through perilymph of scala vestibuli Wave ends at round window, causing it to bulge outward into middle ear cavity 4. Waves with frequencies below threshold of hearing travel through helicotrema & scali tympani to round window 5. Sounds in hearing range go through cochlear duct, vibrating basilar membrane at specific location, according to frequency of sound

Information Processing in the Retina

• Photoreceptors & bipolar cells generate only graded potentials (EPSPs & IPSPs), not APs When light hyperpolarizes photoreceptor cells, they stop releasing inhibitory neurotransmitter to biopolar cells --> Bipolar cells (no longer inhibited) depolarize & release excitatory neurotransmitter onto ganglion cells --> Ganglion cells generate APs transmitted in optic nerve to brain

External ear

• Pinna surrounding ear canal funnels sound waves into auditory canal • External acoustic meatus (auditory canal) —lined with hairs, sebaceous glands, ceruminous glands — transmits sound waves to eardrum • Tympanic membrane (eardrum) vibrates in response to sound, transferring energy to bones of middle ear - Boundary between external & middle ears - Thin, translucent connective tissue

Phototransduction

• Process by which pigment captures light energy, which is converted into graded potential • Capturing light - Deep purple pigment of rods is rhodopsin • Arranged in rod's outer segment • Three steps of rhodopsin formation & breakdown: - Pigment synthesis - Pigment bleaching - Pigment regeneration - (Similar process in cones, but different types of opsins & cones require more intense light)

The Cristae Ampullares

• Receptor for rotational acceleration is crista ampullaris (crista) - Small elevation in ampulla of each semicircular canal • Cristae are excited by acceleration & deceleration of head - Major stimuli are rotational (angular) movements, such as twirling of the body - Semicircular canals are located in all three planes of space, so cristae can pick up on all rotational movements of head

Resonance of the Basilar Membrane

• Resonance: movement of different areas of basilar membrane in response to a particular frequency • Basilar membrane changes along its length: - Fibers near oval window are short & stiff --> Resonate with high-frequency waves - Fibers near cochlear apex are longer, floppier --> Resonate with lower-frequency waves • So basilar membrane mechanically processes sound even before signals reach receptors

Visual Pigments

• Retinal: key light-absorbing molecule that combines with one of four proteins (opsins) to form visual pigments - Synthesized from vitamin A • Four opsins are rhodopsin (found in rods only), & three found in cones: green, blue, red (depending on wavelength of light they absorb) - Cone wavelengths do overlap, so same wavelengths may trigger more than one cone, enabling us to see variety of hues of colors • Example: yellow light stimulates red & green cones, but if more red are triggered, we see orange

photoreceptors

• Rods (A) & cones (B) = modified neurons • Consists of cell body, synaptic terminal, & two segments: - Outer segment: light-receiving region; portioned into discs • Contains visual pigments (photopigments) that change shape as they absorb light - Inner segment of each joins cell body •Photoreceptors are vulnerable to damage - Degenerate if retina detached - Destroyed by intense light - Vision is maintained because outer segment is renewed every 24 hours • Tips fragment off & are phagocytized

Comparing Rod and Cone Vision

• Rods are very sensitive to light, making them best suited for night vision & peripheral vision - Contain a single pigment, so vision is perceived in gray tones only - Pathways converge (as many as 100 into one ganglion), causing fuzzy, indistinct images • Cones have low sensitivity, so require bright light for activation - React more quickly than rods - Have one of three pigments, which allow for vividly colored sight - Nonconverging pathways (some cones have their own ganglion cell) result in detailed, high-resolution vision

Cavity of Cochlea Divided into Three Chambers

• Scala vestibuli - Abuts oval window, contains perilymph - Continuous with scala tympani at helicotrema (apex) • Scala media (cochlear duct) - Separated from scala vestibuli by vestibular membrane - Contains endolymph, secreted by stria vascularis - Basilar membrane comprises "floor", supports spiral organ • Contains cochlear hairs cells, inner & outer • Scala tympani - Terminates at round window, contains perilymph

Extrinsic Eye Muscles

• Six straplike eye muscles • Originate from bony orbit & insert on eyeball • Enable eye to follow moving objects, maintain shape of eyeball, & hold it in orbit • Four rectus muscles; names indicate movements - Superior, inferior, lateral, & medial rectus • Two oblique muscles move eye in vertical plane & rotate eyeball - Superior & inferior oblique muscles

Middle Ear Anatomy

• Small, air-filled, mucosa-lined cavity in temporal bone - Flanked laterally by eardrum & medially by bony wall containing oval & round membranous windows • Pharyngotympanic tube: connects middle ear to nasopharynx - Formerly called eustachian tube - Usually flattened tube, but can be opened by yawning or swallowing to equalize pressure in middle ear cavity with external air pressure • Tympanic membrane cannot vibrate efficiently if pressures on both sides are not equal (sounds are distorted)

Semicircular Canals

• Three canals oriented in three planes of space: anterior, lateral, posterior - Anterior & posterior are at right angles to each other, whereas lateral canal is horizontal - Membranous semicircular ducts line each canal & communicate with utricle - Enlarged area of each duct houses equilibrium receptor region called crista ampullaris • Receptors respond to angular (rotational) movements of head

Structure of the Ear

• Three major areas: - External (outer) ear: hearing only - Middle ear: hearing only - Internal (inner) ear: hearing & equilibrium • Receptors for hearing & balance respond to separate stimuli & are activated independently

Auditory Ossicles

• Three small bones in middle ear, named for their shape: - Malleus: "hammer"; secured to eardrum - Incus: "anvil" - Stapes: "stirrup"; base fits into oval window • Malleus articulates with incus, which articulates with stapes • Suspended by ligaments; transmit vibratory motion of eardrum to oval window