special senses Flashcards by L M

dominant sense

vision

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Outer layer made up of avascular connective tissue

fibrous layer

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sclera

“white” of the eye

protects eye muscle anchoring site

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Anterior portion; transparent; well innervated and responds reflexively to touch; able to regenerate
It has no blood vessels, so it is beyond the reach of the immune system
It is the only part of the body that can be transplanted with little fear of rejection

cornea

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eye’s Middle layer; pigmented

vascular layer

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Blood vessels here nourish all eye layers; melanocytes produce melanin to absorb light (to prevent it from reflecting and scattering)

choroid

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Consists mostly of smooth muscles that control lens shape

ciliary body

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Colored part of eye; pupil
Elastic fibers unique like fingerprints before birth!
eyes are due to light scattering in unpigmented regions

Iris

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only see dimly lit stars through peripheral vision

better looking at dim light

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allows light to enter

pupil

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retina

inner layer (pigmented and neural layer)

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pigmented layer

single layer of cells
pigment absorbs light and prevents scattering
phagocytes, photoreceptor cell renewal
store vitamin A for photoreceptor cells

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neural layer

direct role in vision

1) photoreceptors (sense light)
2) signal bipolar cells
3) signal ganglion cells (generate AP)

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rods

light

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cones

color

blue, green, red cones

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how many photoreceptors?

250 million

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optic disc

where optic nerve leaves the eye

where brain fills in blind spot

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macula lutea

lateral to optic disc

center is called fovea centralis, only contains cones

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Cone density decreases away from fovea

Rod density increases away from fovea, so rods dominate the periphery
don’t look directly dim star if you want to see it!

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Clouding of the lens

cataracts

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Divides eye
Biconvex, transparent, flexible, avascular
Changes shape to allow our eyes to focus near or far
anucleate cells

lens

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aqueous humor

Fluid similar to blood plasma that fills anterior segment

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drainage of aqueous humor is blocked, it can cause high intraocular pressure, compressing retina & optic nerve

glaucoma

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vitreous humor

“Jelly” in posterior segment
Transmits light; provides support; intraocular pressure
born with it

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Cornea =.> Aqueous humor =>Lens =>Vitreous humor =>Entire neural layer of retina to reach photoreceptors

light pathway

light refracted 3 times

enters cornea enters lens leaves lens

lens

image upside-down and left-right reversed

accomodation

lens changes shape to focus on near objects

presbyopia

lens is non-accommodating, why older people have to read text at arm's length

nearsightedness or farsightedness is not due to lens problem, it is...

misshapen eyeball

myopia=nearsighted

hyperopia=farsightedness

optic nerve

axons of ganglion cells in retinal neural layer

phototransduction

hyperpolarization serves as the activation signal, rather than depolarization

optic chiasma

Fibers from medial aspect of each eye cross over, and now fibers belong to optic tracts

Each carries information from same half of visual field | Left optic tract contains info for right half of visual field and vice versa

optic tracts

Primary visual cortex fuses image from each eye to create...

depth perception

panoramic vision

the hunted

olfactory epithelium

Organ of smell Pseudostratified epithelium Poorly located at roof of nasal cavity (air doesn’t easily get to it)

olfactory sensory neurons

regenerate (30-60 days)

we have about (blank) smell genes

400

Each sensory neuron only expresses...

one type of odor receptor protein

fungiform papillae

About 10,000 taste buds | Mostly located on tongue mushroom-shaped

taste cells

Gustatory epithelial cells

each cell can only taste one type of taste, but each bud has...

all of them

Long microvilli that serve as the sensitive portion of the cell that contains membrane receptors; extend through taste pore to epithelial surface

gustatory hairs

Stem cells replace gustatory epithelial cells 7-10 days

basal epithelial cells

6 taste sensations

``` Sweet salty sour bitter umami (maybe) fat ```

taste is 80% smell

yes

MSG

umami flavor

bitter

warning taste

wine tasting is...

snobbish nonsense

hearing only

external and middle ear

hearing and equilibrium balance

internal ear

cerumen

earwax

ceruminous glands

Sebaceous glands and modified apocrine sweat glands

timpanic membrane

transmits energy to bones of middle ear

know hammer, anvil stirrup on slide 22

yes

links middle ear to nasopharynx (upper throat)

pharyngotympanic tube

auditory ossicles

3 smallest bones in body | Transmit vibration of eardrum to oval window, which sets fluids of internal ear into motion

internal ear

bony labyrinth perilymph (similar to CSF) sac (membranous labyrinth filled with endolymph, similar to potassium rich fluid)

3 regions of bony labyrinth

vestibule semicircular canals cochlea

vestibule and semicircular canals

vestibular apparatus

Spiral-shaped and size of a split pea 3 chambers Cochlear duct (middle chamber) contains the spiral organ (hearing receptors) Spiral organ rests on top of basilar membrane, which plays key role (unique structure)

cochlea

(division of vestibulocochlear nerve (VIII)) transmits impulses to brain

cochlear nerve (hearing)

sound

Pressure disturbance; alternating high and low pressure regions

frequency

of waves that pass a given point in a given amount of time

amplitude

Height of wave; represents differences in pressure; related to energy Higher amplitude = more energy = louder sound

resonance

Maximum movement at a particular frequency

basilar membrane

responds to different frequencies of sound

microvilli in ear

stereocilia, moved by basilar membrane

membrane on top of hair cells

moved one way is depolarized, moved other way is repolarized

hearing pathway

Sound (vibration in air)=>Eardrum=>Auditory ossicles=>Internal ear fluids=>Membranes=>Hair cells=>Neurons=>Signal to brain

How do we perceive loudness?

more frequent AP's

How do we perceive pitch?

spot on basilar membrane

vestibular apparatus

maculae and cristae ampullares

maculae

in vestibule linear acceleration and position of head compared to gravity two sacs called saccule and utricule

cristae ampullares

detect rotation of head each semicirc canal oriented in one of 3 planes of space respond to changes in velocity (not airplane)

hairs embedded in

otolith membrane, which moves

otoliths

CAC03 cover membrane, increase inertia

in crista ampullaris

Gelled mass that contains hair cells rotational movement (ampullary cupula)

(division of vestibulocochlear nerve (VIII)) transmits impulses to brain

vestibular nerve