Special Senses (ch. 8)

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what are your special senses?

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1

what are your special senses?

smell, taste, sight, hearing, equilibrium

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2

what are your special sense receptors?

large, complex sensory organs (eye and ear)

localized clusters of receptors (taste buds and olfactory epithelium)

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3

how many receptors are in the eye?

70% of all sensory receptors are in the eye

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4

what are the accessory structures of the eye?

extrinsic eye muscles, eyelids, conjunctiva, lacrimal apparatus

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5

eyelid

opens and closes to protect the eye

meet at medial and lateral commissure (canthus)

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6

eyelashes

glands secrete different lubricants to moisture and protect eye

2 types of glands

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7

tarsal glands

produce an oily secretion that lubricates the eye

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8

ciliary glands

located between the eyelashes

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9

conjunctiva

membrane that lines the eyelid and eyeball

connects with the transparent cornea

secretes mucus to lubricate the eye and keep it moist

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10

Lacrimal apparatus

lacrimal gland and ducts

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11

lacrimal gland

produces lacrimal fluid

situated on lateral end of the eye

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12

lacrimal fluid

tears

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13

path of tears

tears drain across the eye into the lacrimal canaliculi, then the lacrimal sac, and into the nasolacrimal duct, which empties into the nasal cavity

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14

tears contain

dilute salt solution

mucus

antibodies

lysozyme (enzyme that destroys bacteria)

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15

function of tears

cleanses

protect

moisten

lubricate the eye

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16

extrinsic eye muscles

6 muscles attach to the outer surface of the eye

produce gross eye muscles

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17

lateral rectus

moves eye laterally

cranial nerve VI -- abducens

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18

medial rectus

moves eye medially

cranial nerve III -- oculomotor

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19

superior rectus

elevates eye and turns it medially

cranial nerve III -- oculomotor

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20

inferior rectus

depresses eye and turns it medially

cranial nerve III -- oculomotor

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21

inferior oblique

elevates eye and turns it laterally

cranial nerve III -- oculomotor

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22

superior oblique

depresses eye and turns it laterally

cranial nerve IV -- trochlear

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23

internal structures of the eyeball

layers/tunics

humors and fluids

lens

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24

how many layers form the wall of the eyeball?

3

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25

what are they three layers of the eyeball?

fibrous layer

vascular layer

sensory layer

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26

humors and fluids

fill the interior of the eyeball

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27

lens divides the eye. . .

into 2 chambers

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28

fibrous layer of the eyeball

sclera and cornea

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29

sclera

white connective tissue layer

seen anteriorly as the white of the eye

holds structure of the eye

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30

cornea

1st area where light enters the eye

transparent, central anterior portion

allows for light to pass through

repairs itself easily

the only human tissues that can be transplanted without fear or rejection due to lack of blood vessels

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31

vascular layer

blood supply

choroid

  • ciliary body

  • iris

    • pupil

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32

choroid

a blood rich nutritive layer that contains pigment (prevents light from scattering)

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33

how is the choroid modified anteriorly?

into two smooth muscle structures

ciliary body and iris

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34

ciliary body

attached to lens by a suspensory ligament called the ciliary zonule

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35

iris

regulates the amount of light entering the eye

the pigmented layer that gives the eye color

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36

pupil

rounded opening in the iris

while within iris, black part is the back of the retina

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37

sensory layer

photoreceptors

retina and rods and cones

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38

how many layers does the retina contain?

2

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39

what are the two layers of the retina?

  1. outer pigmented layer absorbs light and prevents it from scattering

  2. inner neural layer contains receptor cells (photoreceptors)

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40

what are the photoreceptors?

rods and cones

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41

electrical signals pass from photoreceptors via __________

two neuron chain

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42

what are the two neurons in a two neuron chain?

bipolar cells and ganglion cells

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43

how do signals leave the retina to go to the brain?

via the optic nerve

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44

optic disk

the blind spot

where the optic nerve leave the eyeball

cannot see images focused on the optic disc because it lacks rods and cones

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45

rods

most are found toward the edges of the retina

allow vision in dim light and peripheral vision

all perception is in gray tones

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46

cones

allow for detailed color vision

densest in the center of the retina

fovea centralis

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47

fovea centralis

lateral to the blind spot

area of the retina with only cones

visual acuity is here

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48

visual acuity

sharpest vision

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49

cone sensitivity

3 types of cones (RBG)

each cone type is sensitive to different wavelengths of visible light

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50

what segments does the lens divide the eye into?

  1. anterior segment

  2. posterior segment

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51

anterior segment

aqueous segment

anterior to the lens

contains aqueous humor

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52

posterior segment

vitreous segment

posterior to the lens

contains vitreous humor

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53

aqueous humor

watery fluid found between the lens and cornea

similar to blood plasma

helps maintain intraocular pressure

provides nutrients for the lens and cornea

reabsorbed into venous blood through the sclera venous canal/canal of schlemm

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54

vitreous humor

gel-like substance

prevents eye from collapsing

helps maintain intraocular pressure

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55

ophthalmoscope

instrument used to illuminate the interior of the eyeball and fundus (posterior wall)

can detect diabetes, arteriosclerosis, degeneration of the optic nerve and retina

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56

light must be focused to a point on the ___ for optimal vision

retina

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57

light is _______ by the cornea, aqueous humor, lens, and vitreous humor

bent/refracted

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58

the eye is set for _______

distant vision (over 20 ft away)

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59

accommodation

the lens must change shape to focus on closer objects (less than 20 ft away)

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60

image formed on the retina is a ________

real image

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61

real images are . . .

reversed L from R

upside down

smaller than the object

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62

optic nerve

bundles of axons that exit the back of the eye carrying impulses from the retina

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63

optic chiasma

location where the optic nerves cross

fibers from the medial side of each eye cross over to the opposite side of the brain

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64

optic tracts

contain fibers from the lateral side of the eye on the same side and the medial side of the opposite eye

synapse with neurons in the thalamus

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65

optic radiation

axons from the thalamus run to the occipital lobe

synapse with cortical cells and vision interpretation (seeing) occurs

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66

pathway of impulses from the retina to the point of visual interpretation

  1. optic nerve

  2. optic chiasma

  3. optic tract

  4. thalamus

  5. optic radiation

  6. visual cortex in occipital lobe of the brain

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67

visual fields

overlap for each eye

each eye sees a slightly different view

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68

binocular vision

results and provides depth perception

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69

depth perception

three-dimensional vision

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70

emmetropia

eye focuses images correctly on the retina (normal vision)

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71

myopia

nearsightedness

distant objects appear blurry

light from those objects fails to reach the retina and are focused in front of it

results from having an eyeball that is too long

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72

hyperopia

farsightedness

near objects appear blurry, whereas distant objects are clear

distant objects are focused behind the retina

results from an eyeball that is too short or from a lazy lens

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73

astigmatism

images are blurry

results from light focusing as lines, not points, on the retina because of unequal curvatures of the cornea or lens

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74

convergence

reflexive movement of the eyes medially when we focus on a close object (going cross eyed when a pen is brought to your nose)

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75

photopupillary reflex

bright light causes pupils to constrict

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76

accommodation pupillary reflex

viewing objects causes PUPILS to constrict

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77

how many senses does the ear house?

2 senses

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78

what are the two senses that the ear houses?

hearing and equilibrium (balance)

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79

what are the receptors in the ear?

mechanoreceptors

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80

how many areas is the ear divided into?

3

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81

what are the divisions of the ear?

external (outer) ear

middle ear

internal (inner) ear

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82

external (outer) ear

auricle (pinna)

external acoustic meatus (auditory canal)

only involved in collecting sound waves

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83

external acoustic meatus (auditory canal)

narrow chamber in the temporal bone

lined with skin and ceruminous (earwax) glands

  • glands secrete cerumen (earwax)

  • cerumen traps foreign objects and repels insects

ends at the tympanic membrane (eardrum)

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84

middle ear cavity (tympanic cavity)

air-filled mucosa-lined cavity within the temporal bone

involved in sense of hearing

located btwn tympanic membrane and by a bony wall with two openings

pharyngotympanic tube

3 bones (ossicles)

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85

what are the two openings in the middle ear?

oval window and round window

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86

pharyngotympanic tube

aka auditory tube

links the middle ear cavity with the throat

equalizes pressure in the middle ear cavity so the eardrum can vibrate

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87

what are the three bones in the middle ear?

the auditory ossicles are the malleus (hammer), incus (anvil), and stapes (stirrup)

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88

function of the auditory ossicles

transmit and amplify vibrations from the tympanic membrane to fluids of the inner ear

vibrations travel from the hammer→anvil→stirrup→oval window of the inner ear

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89

internal (inner) ear

includes sense organs for hearing and balance

bony labyrinth/osseous labyrinth

filled with perilymph (bony labyrinth)

filled with endolymph (membranous labyrinth)

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90

what does the osseous labyrinth consist of?

cochlea

vestibule

semicircular canals

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91

spiral of corti

located within the cochlear duct

receptors= hair cells on basilar membrane

gel-like tectorial membrane is capable of bending hair cells

cochlear nerve attached to hair cells transmits nerve impulses to auditory cortex on temporal lobe

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92

pathways of vibrations from the sound waves

  1. auricle (pinna)

  2. external acoustic meatus (auditory canal)

  3. Tympanic membrane

  4. ossicles amplify the sound waves

  5. oval window

  6. basilar membrane in the spiral organ of corti

  7. hair cells of the tectorial membrane are bent when the basilar membrane vibrates against it

  8. an AP starts in the cochlear nerve (cranial nerve VIII)

  9. impulse travels to the auditory cortex in the temporal lobe

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93

high pitched sounds

disturb the short, stiff hairs/fibers of the basilar membrane

  • receptor cells close to the oval window are stimulated

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94

low pitched sounds

disturb the long, floppy hairs/fibers of the basilar membrane

  • specific hair cells further along the cochlea are affected

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95

equilibrium

2 types

  • static

  • dynamic

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96

equilibrium receptors

vestibular apparatus

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97

static equilibrium

balance concerned with changes in the position of the head

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98

maculae

receptors in the vestibule

report on position of the head

help us keep our head erect

send info via vestibular nerve to the cerebellum of the brain

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99

anatomy of the maculate

hair cells are embedded in the otolithic membrane, otoliths float in a gel around hair cells, movements cause otoliths to roll and bend hair cells

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100

dynamic equilibrium

sense that reports on the rotatory or angular movements of the head in space

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