physio e3l2: eyes and ears

3 layers of eye

1. outer

   1. sclera

   2. cornea

2. middle

   1. choroid

   2. ciliary body

   3. iris + pupil

3. inner

   1. retina + photoreceptors

   2. fovea = sits on macula, highest # of cones

   3. optic disk (blind spot)

1. fovea

2. 2 parts of ciliary body

3. what wavelengths are visible light

1. fovea = sits on macula, highest # of cones

2. ciliary body

   1. zonular fibers (suspensory ligaments)

   2. ciliary muscle

3. 350-750 nm

2 fluid filled chambers in eye, what humors?

1. anterior segment = aqueous humor

   1. nourish the lens

2. posterior segment = vitreous humor

   1. gel-like, provides structure to eye

blind spot:

1. why do we have it

2. both eyes?

1. optic disk (optic nerve + blood vessels) = no retina

2. not visible if both eyes open = brain fills in picture

refraction:

1. what is it

2. 3 factors that influence degree of refraction

1. refraction = if not perpendicular, light waves bend as they pass from one medium disunite to another

2. 3 factors

   1. density difference

   2. angle of light waves

   3. curve of cornea and lens, which refract light as it enters the eye

concave v convex + effect on light

cornea and lens:

1. what do they do together

2. what are they individually responsible for

   1. level of curve?

1. refract light to create image

2. cornea = 3X more refraction than lens

   1. curve is fixed

3. lens = allows focusing

   1. curve is adjustable via ciliary + suspensory ligament (zonular fibers)

1. ciliary muscle and suspensory ligaments have ____ actions

2. what does that mean?

3. accommodation reflex

4. how does it work: for far object, for near object?

1. opposing

2. if one is contracting the other is relaxing

3. shifting focus from far to near

4. near object = increase curve

accommodation:

1. 3 parts involved

2. near v. far away objects:

   1. sympathetic or parasympathetic

   2. converge or diverge?

   3. puil contract or open?

   4. 3 steps

1. ciliary muscle → zonular fibers → lens

2. near:

   1. parasympathetic

   2. eyes converge

   3. pupil contracts

   4. close = CMus contracts → ZFib relax → lens bulge

1. far:

   1. sympathetic

   2. eyes diberge

   3. pupil opens

   4. far = CM relax → ZFib contract → lens flattens

emmetropia, myopia, hyperopia

1. what does the eye look like

2. where does the light focus

3. visual acuity?

4. near or far sighted?

5. -ve or +ve? (eye prescription)

6. what lens will fix?

1. emmetropia:

   1. eye circular, light on retina, VA = 20/20 = 1

2. myopia:

   1. eye large/oblong, light in front (near sighted), VA < 1 (10/20), concave lens (-ve) fixes

3. hyperopia:

   1. eye short, light behind (far sighted), VA > 1 (40/20), convex lens (+ve)

Visual acuity:

1. what is the numerator/denominator

2. VA < 1 =

3. VA > 1 =

1. d (in ft) subject can see chart v. the norm

2. myopia

3. hyperopia

1. astigmatism:

   1. 2 causes, which is the usual culprit?

   2. what is the result

   3. draw it

2. 
   

1. Irregularity in cornea thickness or lens curve

2. blurry image = light hits retina but varies in location

1. presbyopia/what is the result

2. cataract/why does it happen

3. glaucoma/what is the result

   1. cupping ?

1. hardening of the lens due to old age = can’t focus on near objects

2. shadowing/ gray/opaque eye behind iris = lens proteins breaking down

3. too much aqueous humor = pressure on CN 2

   1. eye bulges out of optic disk hole

Lens Rx:

1. left v right eye

2. + or - number = what ?

3. what if cylinder and axis #s on Rx?

   1. what do they do?

4. 1 # on Rx v. 3 #s on Rx?

5. which eye is worse

1. OD (oculus dexter) v. OS (oculus sinister)

2. + = hyperopia (far sighted), - = myopia (near sighted)

3. astigmatism

   1. cylinder = correction

   2. axis = location

4. 3 = near/far + astigmatism, 1 = near/far

5. smallest absolute value on Rx

2 parts iris:

1. what do they do

2. sympathetic or para?

1. inner circular muscle = constrictor

   1. para

2. outer radial muscle = dilator

   1. sympathetic

what do these eye muscles do:

1. rectus

2. oblique

3. ciliary

4. elevator papillae

5. constrictor/dilator

1. move that direction

2. rotation

3. focus/accomdation/zoom in

4. upper eyelid

5. iris/pupil size

eye muscle innervations of:

CN 3 = 5 muscles

CN 4 = 1 muscle

CN 6 = 1 muscle

1. oculomotor nerve

   1. inferior, medial, and superior rectus

   2. inferior oblique

   3. elevator papillae

   4. constrictor muscle of iris

   5. ancillary muscle

2. trochlear = superior oblique

3. abducens = lateral rectus

1. 3 steps of light in retina

2. 2 spots of convergence

1. rod/cone photoreceptors -(convergence)→

2. bipolar cells -(convergence) ganglion cells →

3. axons of ganglion cells form CN 2 (optic nerve)

Macula lutea:

1. what is it

2. what is it responsible for

3. what is macular degeneration?

   1. 2 types

      1. angiogenesis

      2. diabetic retinopathy

4. what is retinitis pigments

1. region of retina w/ high cones

2. central vision

3. lose central vision

   1. dry

   2. wet

      1. angiogenesis = making new blood vessels

      2. diabetic retinopathy

4. pigments on the retina affect the macula

1. distribution of rods and cones

2. 3 types of cones

   1. does each type only see one color?

1. rods = periphery, on the sides

2. cones = fovea, center, 0 degrees

1. blue (S)

2. Green (m)

3. Red (L)

4. each type responds best to but not exclusively its color

1. color perception =

2. opponent-process theory

3. color adaptation

4. color blindness affects who

1. cone comparison

2. some colors inhibit perception of other and vice versa

   1. high red, low green / high green, low red

   2. same for blue- yellow

   3. same for black-white

3. staring at color then shifting gaze and get ghost image of opposite color^

4. 4% of men

neural pathway for vision (lab):

1. 3 parts in pathway

2. what happens to nasal and retina axons in optic chiasm?

3. why does a tumor on the pituitary gland result in peripheral vision loss

1. CN 2

2. optic chiasm

   1. nasal retina axons = contralateral

   2. temporal retina axons = ipsilateral

3. optic tract

1. presses on the optic chiasma

depth of perception:

1. what is it

2. how does it form

3. what is one eye’s visual field?

1. getting a 3D image

2. binocular visual field = overlapping of the left and right visual fields (central vision) = 3D image

3. each eye has central and peripheral vision, central overlaps

CN 8:

1. what is it

2. 2 parts / what they do

   1. structure

1. vestibulacochlear nerve

2. vestibule = balance

3. cochlea = hearing

   1. snail-like structure

ear anatomy outside → inside:

1. 2 parts outer ear

2. 4 parts middle ear

3. 2 parts inner ear = what job?

4. other

1. outer

   1. pinna = ear lobe

   2. external auditory meatus = ear canal

2. middle

   1. tympanic membrane

   2. ossicles

      1. mallus

      2. incus

      3. stapes

   3. oval and round windows

3. inner = transduction of sound E

   1. cochlea

   2. vestibular apparatus

4. Eustachian tube (auditory canal) = pressure equilibrium

1. loudness:

   1. what is it

   2. units, scale?

   3. coding + how coded?

2. pitch:

   1. what is it?

   2. units

   3. coding + how coded? where do high/low freq sounds vibrate?

1. loudness = sound wave amplitude

   1. dB = logarithmic

   2. intensity coding = degree of deflection and opening of stereo cilia ion channels

2. Pitch = sound wave freq

   1. Hz = waves/sec

   2. frequency coding = location of deflection on the basilar membrane

      1. high freq = basilar membrane deflected close to oval window

      2. low = deflect at helicotrema (end of cochlea)

1. 2 steps of sound amplification in middle ear.

   1. what happens at each step

2. what in general is causing the amplification?

3. 2 steps how does the cochlea work?

4. round window?

1. sound enters at tympanic membrane = membrane vibrates at sound freq

2. 1st amp = increase vibration at each ossicle

3. 2nd amp = movement of oval window

1. large to small surface areas (tymp. mem. → oval window) = amplification

1. last ossicle, the stapes, vibrates → oval window (membrane) vibrates → cochlea fluid vibrates

1. its another cochlear membrane that will bend/bulge out to protects cochlea from high pressure waves

Cochlea structure:

1. where does sound enter

2. 3 layers

3. 2 lymphs. diff b/t / where

4. 2 membranes?

1. oval window

2. scalavestibuli and scalatympani

   1. perilymph

3. scala media = where the magic happens

   1. endolymph = more K+ than peri

   2. basilar membrane = where hair cells of the organ of court (sensory tissue) sit

   3. tectorial membrane = hold cilia of hair cells still so not randomly activated

1. what is the functional unit of the ear? in what 2 ways?

2. hair cell structure

3. how hair cells activate (depolarize +)

   1. why?

1. hair cell

   1. movement translated into electrical signals; branches of hair cells form CN 8

2. structure

   1. kinocilia = long fiber

   2. 2 stereo cilia = 2 short fibers

   3. tip links = connect ciao and stereo = move together

3. cell activation

   1. cilia move toward kino = depolarize +

   2. toward stereo = repol -

4. cilia move towards kino = opens hair cell K+ gate. endolymph high in potassium = AP → Ca+ opens + neurotransmitters

semicircular canal and macula:

1. what is their job

2. similar structure to cochlea

3. different structure to cochlea

4. 2 parts macula

1. function

   1. macula = linear balance.

   2. ss canal = rotational balance

2. hair cells and how they work/depolarize (depolarize towards kinocilia)

3. not called tectorial membrane (what holds hair cells still)

   1. macula = otolithic membrane

   2. ss canal = cupula (gelatinous)

4. utricle and saccule

1. one hair cell =

2. what are the 2 branches of CN 8 made of?

3. where do they go

1. one cochlear nerve of cn 8

2. cochlea hair cells → cochlear branch of CN 8

3. ss canal and vestibule hair cells → vestibular branch of CN8

4. merge into vestibularcochlear → thalamus → auditory cortex for tonotopic/topographical arrangement

1. conductive deafness

2. sensorineural deafness =

3. central deafness

1. conductive deafness = problem in external/middle ear

2. sensorineural deafness = inner ear or CN8

3. central deafness = damage outside the ear like a brain tumor

1. 2 steps how does ss canals detect rotation

2. what direction is depolarized?

3. 3 ss canals/ what they do

1. head rotation = acceleration; hair cells on opposite side of head are oriented differently

   1. depolarization on one side (hair cells moved toward kinecilia), hyperpol on other

2. post rotation = deceleration; opposite effect

3. ss canals

   1. anterior canal = nodding = head movement up/down on axis

   2. posterior canal = tilting head to shoulder = left/right on axis

   3. lateral/horizontal canal = turning head side to side