SPECIAL SENSES

internal ear

*2 divisions bony labyrinth = cave/system of channels; 3 regions 1. vestibule 2. semicircular canals 3. cochlea membranous labyrinth → series of interconnected membranous sacs & ducts → houses receptors for hearing & equilibrium → filled w endolymph

perilymph & endolymph

Conduct sound vibrations involved in hearing → respond to mechanical forces occurring during changes in the body position and acceleration

describe the path of light from the point where it enters the eye until the photoreceptors are stimulated, noting each structure through which the light passes

Cornea → aqueous humor → lens → vitreous humor → overlying cells of neural layer of retina → photoreceptors → bipolar → ganglia

identify in order the structures or materials through which light passes as it moves from the air to the retina

Cornea → aqueous humor → lens → vitreous humor → overlying cells of neural layer of retina → photoreceptors → bipolar → ganglia

photopigments

all have 2 parts: 1. retinal → key absorbing molecule → combines w one of 4 opsins to form visual pigments → cis form is bent; trans form is linear 2. opsins → 4 diff types of glycoproteins (rhodopsin in rods and 3 others in cones) → differs from one pigment to another

which of the papillae identified above (#47) contain taste buds?

all of them -- except filiform

continuation of pathway to brain

axons of retinal ganglion cells form optic nerve → medial fibers from each eye cross over at optic chiasm and continue on as optic tract →→ each optic tract carries info from same half of visual field to primary visual cortex → most tracts continue to lateral geniculate nucleic of thalamus →→ from there, fibers of 2nd order thalamic neurons form optic radiation which projects to primary visual cortex → conscious perception of visual images occurs in cerebral cortex

refraction

bending of light rays when they pass from a medium of one density to a medium of different density

olfactory receptor cells are an example of what type of neuron?

bipolar neuron

activation thresholds for primary tastes - rank

bitter is least threshold sour salty umami & sweet

which of the primary tastes uses a G protein mediated mechanism

bitter, sweet, umami

convergence of eyeballs

caused by medial rotation of eyeballs → convergence of eyes toward object being viewed

vestibule

central egg shaped cavity of bony labyrinth contains 2 membranous sacs 1. saccule = continuous w cochlear duct 2. utricle = continuous w semicircular canal

how do the above structures work together in accomodation for near vision?

ciliary muscles contract → loosens the zonule → allows lens to bulge

how does iris modify amount of light that enters the posterior segment of the eye?

close vision & bright light → sphincter pupillae (circular) contracts → pupils constrict distant vision & dim light → dilator pupillae (radial) contracts → pupils dilate allowing more light to enter

what is the functional significance of the near point of vision? Describe the typical agerelated changes in the near point of vision.

closest point that you can see close up → point you can see clearly is closer with children → point u can read close will gradually get farther

lacrimal apparatus

consists of lacrimal gland, lacrimal canals, & ducts lacrimal gland → continually releases a dilute saline solution (lacrimal solution) into superior part of conjunctival sac duct → tears drain into here → empties into nasal cavity at inferior nasal meatus canal → drains secretion into the lacrimal sac

wall of eyeball

contains 3 layers (tunic) 1. fibrous layer → includes sclera & cornea →→ cornea is most anterior →→ sclera is white, fibrous, collagenous part of eyeball 2. vascular layer → inclues choroid, ciliary body, iris →→ choroid is posterior; other 2 are anterior 3. sensory layer → includes retina function??

how are frequency and intensity of sound vibrations encoded by the spiral organ?

depending on frequency, the sound vibrates in a certain place → higher frequency = heard at beginning of tube by short hair cells

which muscle layer of iris is under sympathetic control?

dilator

semicircular canals

each oriented in one of 3 planes of space membranous semicircular duct within each canal → continuous w utricle → each duct ends w ampulla (enlarged area) which contains the receptor for dynamic equilibrium (crista ampullaris)

where is endolymph in cochlea? where is perilymph?

endoylymph = scala media perilymph = scala vestibuli & tympani

which cranial nerves are involved in gustation? what is the location of the taste buds associated w each of CNs?

facial nerve (CN VII) → buds in anterior 2/3 of tongue glossopharyngeal nerve (CN IX) → buds in posterior third & pharynx vagus nerve (CN X) → buds in epiglottis & lower pharynx

perilymph

fills the bony labyrinth → membranous suspended in it similar to CSF ?

which region of retina produces sharpest vision?

fovea centralis → small pit at center of macula lutea why? → retinal structures are displaced to sides here (light passes directly to photoreceptors) → contains only cones

which cells generate an AP?

ganglion

What part of the gustatory receptor cell is the stimulus transducer?

gustatory hairs G-protein coupled receptors on membrane

amplitude

height of crests correlates to intensity of sound perceive as loudness unit = decibels (dB)

endolymph

interior of bony labyrinth contains this chemically similar to K+ rich intracellular fluid ?

how does the release of activated opsin during this cycle alter the rate of neurotransmitter release by photoreceptor cells?

isomerization of retinal & release of opsins cause enzyme to break down cGMP causes Na channels to close and the inhibition of glutamate release HYPERPOLARIZATION

what happens when a photoreceptor cell is exposed to light?

isomerization of retinal activates enzyme that breaks down cGMP → no cyclic GMP around to bind → inflow of cations slows/stops *hyperpolarizing receptor potential → closes Ca ion channels & turns off/slows release of glutamate → excited bipolar cells

focusing for close vision

light from close objects (<6 m) diverges requires eye to make adjustments using 3 processes 1. accommodation of lenses 2. constriction of pupils 3. convergence of eyeballs

what type of tissue comprises the conjunctiva?

loose CT

changes in amplitude are interpreted as changes in

loudness → interpretation of sound intensity

what occurs in the optic chiasm

medial fibers from eye cross over here

what two regions are connected by the auditory tube? how does the auditory tube contribute to hearing?

middle to pharynx helps equalize pressure in ear cuz pressure inside & outside have to be equal

oblique muscles

move the eye in vertical plane when eyeball is already turned medially by rectus muscles 1. superior oblique → originate w rectus muscles, runs along wall of orbit, and pass through trochlea → innervated by trochlear nerve → depress & lateral 2. inferior oblique →originates from medial orbit surface and run laterally/obliquely to eye furface → innervated by oculomotor nerve → elevate & lateral *allows eyes to be directly elevated or depressed

refraction abnormalities

myopia (nearsightedness) → light from distant object is brought into focus before reaching retina → distant objects focus in front of retina rather than on it → eyeball is too long relative to accommodation ability of lens → distant objects are blurred hyperopia (far-sightedness) → light from close object is brought into focus behind retina → eye is too short relative to focusing power of lens astigmatism → unequal curvature in diff parts of cornea or lens → lead to blurry images

frequency

number of waves that pass a fixed reference point in a given time measure it by measuring wavelength → shorter wave = higher frequency → distance between 2 peaks unit = cycles per second (cps) → 1 Hz = 1cps

specific site of olfactory transduction

olfactory cilia membrane

spiral organ *relationship to basilar & tectorial membranes?

organ of corti *sits on basilar membrane → composed of supporting cell & cochlear hair cells → hair cells arranged in 4 rows along membrane (1 row of inner hair cells; 3 rows of outer hair cells) → long hairs enmeshed in gel-like tectorial membrane *afferent nerve fibers coil around base of hair cells & form cochlear branch of CN VIII

rectus muscles

originate from a common tendinous ring in the posterior orbit and insert onto the outer surface of the eye 1. superior rectus → innervated by oculomotor n 2. inferior rectus → innervated by oculomotor n 3. lateral rectus → innervated by abducens n. 4. medial rectus → innervated by oculomotor n *produce all eye movements we require → superior & inferior cannot elevate or depress without also turning it medially

palpebral vs bulba conjunctiva

palpebral → lines eyelids bulbar → fold back over anterior surface of eyeball → covers only white of eye → very thin → blood vessels are clearly visible beneath it

which cell layer transduces visible light energy?

photoreceptors

What are the primary functions of the pigmented layer with respect to clear vision?

pigments absorb light & prevent it from scattering through eye → if light bounced in eye, we would not have good visual acuity

when frequency varies, we perceive changes in

pitch → perception of different frequencies → higher frequency = higher pitch

structural relationship between ciliary body, ciliary processes, ciliary zonule, & lens of eye

posterior surface of ciliary body has ciliary processes (radiating folds) → these processes secrete fluid that fills cavity → ciliary zonule extends from ciliary processes to the lens & helps hold lens in position

eyelashes

protect free margin of each eyelid glands secrete fluids that lubricates eyelids & prevent them from sticking together very sensitive cuz many nerves if anything touches you blink

Are olfactory receptors considered to be rapid or slow adapting?

rapid adapting neurons are sensitive

which of the primary tastes is associated with a transduction process involving Na+ inflow across the membrane of the gustatory hair?

salty

fibrous layer

sclera → bulk of fibrous layer → glistening white & opaque → tough, tendon-like → protects & shapes eyeball → provides sturdy anchoring site for eye muscles → continuous w dura mater cornea → crystal clear → forms a window that lets light enter eye → major part of light bending apparatus → epithelial sheets cover both faces →→ external = stratified squamous; protects cornea from abrasion; merges w bulbar conjunctiva →→ internal (corneal endothelial) = simple squamous; lines inner face; sodium pumps to maintain clarity → supplied w nerve endings (mostly for pain) → no blood vessels

eyebrows

short, coarse hairs that overlie the supraorbital margins of the skull *help shade the eyes from sunlight *prevent perspiration trickling down forehead from reaching eyes

extrinsic eye muscles - function

six of them *control movement of each eyeball → allow eyes to follow moving object → help maintain shape of eyeball → hold eyeball in orbit

which of the primary tastes is mediated by H+

sour

which muscle layer of iris is under parasympathetic control?

sphincter

rods vs cones

structure?

2 muscles of middle ear

tensor tympani and stapedius → reduce vibration of ossicles when its really strong so inner ear wont get damaged → protection

what is the dark current?

this refers to the depolarizing dark current that occurs when the rod is dark on left → cyclic GMP binds to Na & Ca gated ion channels and holds them open → the continuous inflow of cations into the photoreceptor cell produces dark current *maintains transmembrane potential of -30 mv (depolarization) → as a result, Ca ion channels in synaptic terminals of photoreceptor cells are held open →→ continuous release of glutamate occurs which inhibits bipolar cells

what is the functional significance of the far point of vision

to look at things that are far off no contraction

sound transduction

transmission of sound: 1. sound waves entering external acoustic meatus strike tympanic membrane → set it vibrating at same frequency → greater intensity = farther membrane is displaced in its vibratory motion 2. motion of tympanic is amplified and transferred to oval window by ossicle lever system → pressure exerted on window is 20x greater (cuz tympanic is bigger) → increased pressure overcomes stiffness & inertia of cochlear fluid and sets it into wave motion 3. stapes rocks bath & forth against oval window -- sets perilymph in scala vestibuli into similar motion → pressure wave travels through perilymph from basal end toward helicotrema two paths from there... 1. helicotrema path → sounds of low frequency create pressure wave that go through cochlea → goes up scala vestibuli, around helicotrema, and back toward round window through scala tympani → sounds do not activate spiral organ -- below range of hearing 2. basilar membrane path → sounds w high frequencies to create pressure waves → short cut -- transmitted through cochlear duct into perilymph of scala tympani → as pressure wave descends through duct, it vibrates basilar membrane →→ vibration activates hair cells causing APs to be sent to brain

optic disc

where optic nerve exit the eye weak spot in posterior wall of eye → not reinforce by sclera AKA blind spot → lacks photoreceptors so light focus on it cannot be seen filled w axons

structure of iris

→ colored part of eye → most anterior portion → lies between cornea & lens; continuous w ciliary body → pupil = round central opening of iris; allows light to enter → includes 2 smooth muscle layers w bunches of sticky elastic fibers (sphincter pupillae & dilator pupillar) → muscle fibers allow it to act reflexively → contains only brown pigment

gustatory pathway

1. CNs receive impulses from various parts of tongue 2. afferent CN fibers synapse in solitary nucleus of medulla 3. from medulla, impulses stream to thalamus & gustatory cortex in insula 4. fibers project to hypothalamus & limbic system structures

middle ear

*auditory tube → connects middle ear to nasopharynx *auditory ossicles 1. malleus = attaches to tympanic membrane → articulates w incus 2. incus → articulates w stapes 3. stapes → vibrates in oval window

outer ear structures

*auricle (pinna) → hands on side of head → mostly cartilaginous → swirls help direct sounds waves to meatus *external acoustic meatus → carries sound to middle ear → boundary is tympanic membrane *tympanic membrane → boundary between external & middle ear → thin translucent CT membrane → vibrates in and out in response to sound & transfers energy to ossicles

internal structure of cochlea *note location of cochlear structures w respect to oval & round windows

*cavity is divided into 3 chambers 1. scala vestibuli → continuous w vestibule → abuts oval window → contains perilymph 2. scala media → cochlear duct → contains endolymph 3. scala tympani → terminates at round window → contains perilymph *2 membranes 1. vestibular membrane → roof of cochlear duct that separates scala media from scala vestibuli 2. basilar membrane → separates scala tympani from scala media → spiral organ sits on it *refer to images in notes

aqueous humor

*clear fluid similar to blood plasma *forms and drains continually location = in anterior segment of internal cavity function → maintains a constant intraocular pressure which helps support the eyeball → supplies nutrients & oxygen to lens & cornea and to some cells of retina → carries away metabolic wastes

vitreous humor

*clear gel that binds water location = posterior segment of cavity functions → transmits light → supports posterior surface of lens & holds neural layer of retina firmly against pigmented layer → contributes to intraocular pressure (helps counteract pulling force of eye muscles)

inner hair cells of spiral organ

*excitation of them results in transduction movement of basilar membrane deflects hairs of inner hair cells hair cells have microvilli that contain many sterocilia (hairs) that bend their base → these project into K+ rich endolymph w longest hairs enmeshed in gel-like tectorial → longest stereocilia in a bundle are connected to shortest ones via vertically oriented tip links →→ tip link filaments connect to spring gated ion channels →→ when tip links are stretched, they open cation selection channels (mechanotransduction) *bending of stereocilia toward tallest ones pull on tip links, causing K+ & Ca2+ ion channels in shorter stereocilia to open → ions flow into cell, creating receptor potential that can lead to release of glutamate →→ release can trigger AP in afferent neurons of cochlear nerve *bending of stereocilia toward shorter ones causes tip links to relax → ion channels close, leading to repolarization and even hypolarization

focusing for far vision

*eyes are best adapted for this → ciliary muscles are reflex here *distance beyond which no change in lens shape is needed for focusing → 20ft for normal eye → cornea & lens focus light on retina *ciliary muscles are relaxed → pulls ciliary zonule --- lens are stretched flat

process through which the tympanic membrane and ossicles work together to transmit and amplify sound waves

*flashcard 96

humors

*internal cavity of eye filled w these fluids 1. aqueous humor 2. vitrous humor

accommodation

*involves increasing lens' curvature to increase refraction → parasympathetic input contracts cililiary muscle → this loosens ciliary zonule; lens bulges *zonule has a ring of collagenous fibers that attach to lens

constriction of pupils

*managed by accommodation pupillary reflex → constriction of pupils to prevent divergent light rays from entering eye →→ such rays would pass through extreme edge of lens and would not focus properly

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 and stretch, which changes stiffness of basilar membrane *ability serves two functions: 1. increase "fine-tuning" responsiveness of inner hair cells by amplifying motion of basilar membrane 2. protect inner hair cells from loud noises by decreasing motion of basilar membrane

olfactory pathway

*olfactory sensory neurons form olfactory nerves that synapse in olfactory bulb (in nasal cavity) → filaments of olfactory nerves here synapse w mitral cells (2nd order sensory neurons in glomeruli) *mitral cells refine the signal, amplify it and then relay it → impulses flow from olfactory bulbs (via olfactory tract) to piriform lob or olfactory cortex *in cortex, 2 pathways take info to various parts of brain → one goes to frontal lobe -- smells are consciously interpreted and identified → one goes to hypothalamus, amygdaloid body, and other regions of brain stem -- emotional responses

photoreceptor cells structure

*resemble tall epithelial cells consistant of 2 main parts 1. outer segment → receptor region → contains photopigments that change shape as they absorb light 2. inner segment → joins cell body → connected to outer via cilium → contains nucleus & cellular organelles → site of ATP & photopigment production → slender process extends from cell body & extends in synaptic terminals

papillae on tongue

*where most taste buds are found peg-like projections of tongue mucosa that make tongue abrasive types 1. fungirom = mushroom shaped → taste buds mainly here → scatted over entire tongue 2. foliate = epithelium of side walls 3. vallate papillae = round & large → least numerous → in the back

vascular layer

1. choroid → blood-vessel rich, dark brown membrane → blood vessels nourish all eye layers → brown pigment helps absorb light, prevent it from scattering and reflecting → has a posterior opening where optic nerve leaves eye 2. ciliary body → choroid becomes this anteriorly → thickened ring of tissue that encircles lens → consists mainly of smooth muscle bundles (ciliary muscles) which control lens shape → also includes ciliary processes & zonule 3. iris → colored part of eye → most anterior portion → lies between cornea & lens; continuous w ciliary body → pupil = round central opening of iris; allows light to enter → includes 2 smooth muscle layers w bunches of sticky elastic fibers → muscle fibers allow it to act reflexively

2 types of hearing loss/deafness

1. conduction deafness → occurs when smth hampers sound conduction to fluids of internal ear → most common causes are middle ear inflammations & otosclerosis of ossicles 2. sensorineural deafness → results from damage to neural structures at any point from cochlear hair cells & auditory cortical cells → usually due to gradual loss of hair cells throughout life → loud noise, high intensity sounds may cause loss of hair cells → degeneration of cochlear nerve, strokes, & tumors are other causes

what two eye structures account for virtually all of the eye's refractive ability

1. cornea → when light strikes it & moves from air to cornea (change in density), refraction occurs → 75% of total refraction → constant & cannot change focus 2. lens → 25% of total refraction → varies in refractive power

cell types of taste buds

1. gustatory epithelial cells → taste cells → gustatory hairs (long microvilli) project from it and extend through taste pore to surface of epithelium →→ sensitive portion of cell → sensory dendrites coiled around cell →→ receive signals from many cells within taste bud 2. basal epithelial cells → act as stem cells → divide and differentiate into new gustatory epithelial cells

describe the process of transduction in an olfactory receptor cell

1. odorants stimulate olfactory sensory neurons by binding to receptors 2. binding activates G proteins which activate enzymes (adenylate cyclases) 3. enzymes synthesize cyclic AMP (cAMP) as a second messenger 4. cAMP acts causes plasma membrane cation channel to open → allows Na+ & Ca2+ to enter 5. Na influx leads to depolarization & impulse transmission 6. Ca influx causes transduction process to adapt → decreases response to sustained stimulus

3 cell types of olfactory epithelial

1. olfactory sensory neurons → pin shaped receptor cells → unusual bipolar neurons → has thin apical dendrite that terminates in a knob → typically lie flat on nasal epithelium → covered by coat of thin mucous produced by supporting cells and glands → nonmyelinated axons are gathered into fasciles that form the filaments of the olfactory nerve → open cation channels to make receptor potential 2. columnar supporting-cells → surrounded and cushioned by neurons → make up bulk of epithelial membrane → contain yellow-brown pigment 3. olfactory stem cells → at base of epithelium → short cells → make new cells

the ear - 3 areas

1. outer ear 2. middle ear 3. inner ear

cell layers of retina

1. photoreceptor cells → outermost 2. bipolar cells 3. ganglion cells → innermost

processing of visual input that occurs in the retina

1. photoreceptors generate receptor potentials → light hyperpolarizes cell → cell stops releasing glutamate (inhibitory) to bipolar cell 2. bipolar cells generate excitatory or inhibitory postsynaptic potentials (EPSPs or IPSPs) → if it does not receive glutamate, it will depolarize and release neurotransmitter onto ganglion cells 3. ganglion cells generate APs which are transmitted to optic nerve in brain *involves convergence (rods converge; cones converge a little) amacrine cells facilitate/inhibit synapses between ganglion & bipolar cells horizontal cells facilitate/inhibit synapses between photoreceptors & bipolar cells

cyclic pathway of photopigment formation & breakdown

1. pigment synthesis → light strikes photopigment & is absorbed by it → causes a cis to trans conversion of retinal → trans cannot combine w opsin -- retinal has to separate 2. pigment bleaching → retinal separates from opsin → products = trans retinal + opsin 3. pigment regeneration → opsin available to combine w another cis retinal to create a new color photopigment → complex conversion of trans retinal to cis retinal → after cis retinal is regenerate & shuttled back to outer segment, it is available to bind w an opsin (new photopigment)

retina layers

1. pigmented layer → outer layer → single cell layer thick → close to choroid → extends anteriorly to cover ciliary body & posterior surface of iris 2. neural layer → inner → extends anteriorly to posterior edge of ciliary body →→ junction w ciliary body is AKA ora serrata

types of photoreceptors

1. rods → dim light & peripheral vision receptors → more numerous → ore sensitive to light → do not provide sharp images or color vision → high convergence 2. cones → vision receptors for bright light → provide high resolution color vision → low convergence

identify and locate w respect to each other the 3 unique regions of the bony labyrinth

1. semicircular canals 2. vestibule 3. cochlea

2 types of equilibrium

1. static → monitor position of head in space → play key role in control of posture → respond to linear acceleration forces but not rotation 2. dynamic → changes in head rotation

What are the 5 primary taste sensations?

1. sweet → elicited by many organic substances 2. sour → produced by acids 3. salty → produced by metal ions 4. bitter → produced by alkaloids, nonalkaloids 5. umami → produced by amino acids glutamate & asparate

eye fatigue

3 mechanisms 1. continuous accommodation 2. pupillary constriction 3. convergence

different extrinsic eye muscles

4 rectus muscles; 2 oblique muscles

eyelids

AKA palpebrae protect eyes blinking spreads mucous

describe auditory pathway from the sensory afferents at the base of the hair cells to the auditory cortex and subcortical areas

transmits info primarily from inner hair cells to cerebral cortex 1. impulses generated in the cochlea pass through the spiral ganglion & along afferent fibers of cochlear nerve to cochlear nuclei of medulla 2. neurons project to the superior olivary nucleus → lies at junction of medulla & pons 3. axons ascend in lateral lemniscus to the inferior colliculus (auditory reflex center) → colliculus project to medial geniculate nucleus of thalamus 4. axons of thalamic neurons project to primary auditory cortex → provides conscious awareness of sound *each auditory cortex receives impulses from both ears

conjunctiva

transparent mucous membranes *lines eyelids as palpebral conjuctiva; folds back over as bulbar conjunctiva → bulbar covers white of eye ?

what structures create the borders of the middle ear

tympanic membrane oval window