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HAN 200 > chapter 15 > Flashcards

chapter 15 Flashcards

1
Q

The eye and vision

A
  • > 70% of all sensory receptors are in the eye
  • nearly half of the cerebral cortex is involved in processing visual info
  • most of the eye is protected by a cushion of fat and bony orbit
  • eye is like a camera
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2
Q

accessory structures of the eye

A
  • protect the eye and aid eye function:
  • eyebrows: shade from sun
  • eyelids (palpebrae): protection/glands
  • conjunctiva: transparent membrane
  • lacrimal apparatus: tears
  • extrinsic eye muscles (CN 3,4,6)
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3
Q

eye muscles controlled by cranial nerves 3,4,6

A

yes

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4
Q

structure of the eyeball

A

wall of eyeball contains 3 layers:

  1. fibrous-sclera and cornea
    * avascular, outermost CT
  2. vascular: iris, ciliary body, choroid. *middle pigmented area
  3. sensory- retina
    * delicate 2 layered membrane
  • internal cavity is filled with fluids called humors
  • the lens separates the internal cavity into anterior and posterior segments (cavities)
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5
Q

fibrous layer

A
  1. sclera (white of your eye):
    - protects and shapes eyeball
    - anchors extrinsic eye muscles
    - continous w/ dura mater of brain posteriorly
  2. cornea:
    - transparent anterior portion of fibrous layer
    - bends light as it enters the eye
    - numerous pain receptors contribute to blinking and tearing reflexes
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6
Q

vascular layer (uvea)- middle pigmented layer

A
  1. choroid region:
    - supplies blood to all layers of the eyeball
  2. ciliary body:
    - smooth muscle bundles (ciliary muscles) control lens shape (accommodation)
  3. iris:
    - the colored part of the eye
    - pupil: central opening that regulates the amount of light entering the eye
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7
Q

what 2 muscles does the iris have and how does it affect the parasympathetic and sympathetic NS system?

A

Iris has 2 muscles:

  • sphincter pupillae
  • dilator pupillae

Parasympathetic division:
sphincter pupillae muscle contraction decreases pupil size

sympathetic division:
dilator pupillae muscle contraction increases pupil size. (think when you in a bad situation, say, running in a forest while being chased, you need to see everything so eyes dilate. fight or flight

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8
Q

sensory layer: retina

A
  1. pigmented layer (outer layer):
    - absorbs light and prevents its scattering
  2. Neural layer (inner layer):
    - photoreceptor- transduce light energy
    - photoreceptors (rods/cones)->bipolar cells-> ganglion cells where action potential is generated
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9
Q

the retina

A

ganglion cell axons:

  • run along the inner surface of the retina
  • leave the eye as the optic nerve (CN 2)

Optic disc (blind spot):

  • site where the optic nerve leaves the eye
  • lacks photoreceptors
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10
Q

Photoreceptors

A
  1. rods:
    - more numerous at peripheral region
    - operate in dim light
    - provide indistinct, fuzzy, non color peripheral vision
  2. cones:
    - found in macula lutea; concentrated in the fovea centralis
    - operates in bright light
    - provide high-acuity color vision

macular degeneration-loss of vision in the center of eye due to damage to the retina

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11
Q

fundus of eye

A

only place where small vessel can be observed directly

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12
Q

internal chambers and fluids

A
  • > Posterior segment contains VITREOUS humor that:
  • transmits light
  • holds the neural retina firmly against the pigmented layer
  • contributes to intraocular pressure
  • > Anterior segment contains aqueous humor:
  • -is composed of 2 chambers-
  • anterior chamber- between the cornea and the iris

*posterior chamber-between the iris and the lens

Glaucoma: compression of the retina and optic nerve if drainage of aqueous humor is blocked. 2nd leading cause of blindness in US

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13
Q

lens

A
  • biconvex, transparent, flexible, elastic, and avascular
  • allows precise focusing of light on the retina
  • lens become denser, more convex, and less elastic with age

Cataracts (clouding of lens) occur as a consequence of aging, diabetes mellitus, heavy smoking, and frequent exposure to intense sunlight

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14
Q

focusing light on the retina

A

pathway of light entering the eye: cornea, aqueous humor, lens, vitreous humor, neural layer of retina, photoreceptors

  • light is refracted (bending of light ray) 3X:
    1. at the cornea
    2. entering the lens
    3. leaving the lens

-change in lens curvature allows for fine focusing of an image

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15
Q

parasympathetic input contracts the ciliary muscle, allowing the lens to bulge and focus on near objects

A

yes

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16
Q

rods

A
  • best suited for night vision (dim light) and peripheral vision
  • perceived input is in gray tones only
  • fuzzy and indistinct images
  • rod pigment: RHODOPSIN, do not detect color. 120 million to 130 million rods, located in periphery
  • night blindness-condition in which rod function is impaired, most common cause is deficit in vitamin A
17
Q

cones

A

functional characteristics:
-need bright light for activation

  • cone pigment: 3 types of pigments, sensitive to primary colors (red, green, blue), 6-7 million cones, located in macula
  • detailed, high-resolution vision
18
Q

light adaptation

A
  • occurs when moving from darkness into bright light
  • large amounts of pigments are broken down instantaneously, producing glare
  • pupils constrict
  • cones and neurons rapidly adapt
  • visual acuity improves over 5-10 min
19
Q

dark adaptation

A

occurs when moving from bright light into darkness

  • cones stop functioning in low-intensity light
  • pupils dilate
  • Rhodopsin accumulates in the dark and retinal sensitivity increases within 20-30 min

takes longer to adapt to dark than it does to light

20
Q

visual pathway

A
  • axons of ganglion cells form the optic nerve
  • some fibers of the optic nerve cross at the optic chiasma
  • most fibers of the optic tracts continue to the thalamus
  • the optic fibers connect to the primary visual cortex in the occipital lobes
21
Q

depth perception

A

both eyes view the same image from slightly different angles

-depth perception (3-dimensional vision) results from cortical fusion of the slightly different images

22
Q

Focusing an object on the _______ provides the highest visual acuity

A

fovea centralis

23
Q

The ear: hearing and balance

A

3 parts of the ear:

  1. external (outer) ear
  2. middle ear (tympanic cavity)- air filled
  3. internal (inner) ear- fluid filled
24
Q

The ear: hearing and balance

A
  • external ear and middle ear are involved with hearing
  • internal ear functions in both hearing and balance
  • receptors (mechanoreceptors) for hearing and balance
  • respond to separate stimuli
25
Q

The cochlea-spiral bony chamber

A

The cavity of the cochlea is divided into 3 chambers:

  • scala vestibuli
  • scala media (cochlear duct)
  • scala tympani
26
Q

physiology of hearing

A
  • sound waves (vibrations in air) cause ear drum to vibrate
  • eardrum vibration causes movement of auditory ossicles (middle ear)
  • ossicle movement presses fluid of inner ear and waves are formed
  • tiny hair cells are excited and stimulate local neurons of Cranial Nerve VIII (8)(vestibulocochlear N)
27
Q

auditory processing

A
  • impulses from specific hair cells are interpreted as specific pitches
  • loudness is detected by increased numbers of action potentials that result when the hair cells experience larger deflections
  • localization of sound depends on relative intensity and relative timing of sound waves reaching both ears
28
Q

equilibrium and orientation

A

-vestibular apparatus consists of the equilibrium receptors utricle/saccule and semicircular canals

A.) Utricle and saccule receptors (in vestibule):
*effects of gravity, linear acceleration (ex: driving in a car)

B.) semicircular canal receptors monitor dynamic equilibrium
*angular movements (ex: spinning)

29
Q

equilibrium pathway to the brain

A
  • pathways are complex and poorly traced
  • impulses travel to the vestibular nuclei in the brain stem then to cerebellum (balance center)
  • 3 modes of input for balance and orientation
  • vestibular receptors
  • visual receptors
  • somatic receptors

HAN 200 (15 decks)

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